U.S. patent application number 10/611801 was filed with the patent office on 2004-07-01 for methods and devices for improving ultrasonic measurements using multiple angle interrogation.
Invention is credited to Lang, Philipp, Mendlein, John D..
Application Number | 20040127793 10/611801 |
Document ID | / |
Family ID | 22104033 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127793 |
Kind Code |
A1 |
Mendlein, John D. ; et
al. |
July 1, 2004 |
Methods and devices for improving ultrasonic measurements using
multiple angle interrogation
Abstract
The invention provides for ultrasonic methods, compositions and
devices, particularly methods, compositions and devices that
provide for interrogating with ultrasonic transducer(s) at multiple
transmission angles in an anatomic region. The invention provides
for improved interrogation devices that reduce tissue artifacts
arising from heterogenous structures in tissues.
Inventors: |
Mendlein, John D.;
(Encinitas, CA) ; Lang, Philipp; (San Francisco,
CA) |
Correspondence
Address: |
HALE AND DORR, LLP
60 STATE STREET
BOSTON
MA
02109
|
Family ID: |
22104033 |
Appl. No.: |
10/611801 |
Filed: |
July 1, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10611801 |
Jul 1, 2003 |
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09071854 |
May 2, 1998 |
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6585649 |
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09071854 |
May 2, 1998 |
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09036940 |
Mar 9, 1998 |
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6013031 |
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Current U.S.
Class: |
600/442 |
Current CPC
Class: |
A61B 8/4281 20130101;
A61B 8/4209 20130101; A61B 8/0875 20130101 |
Class at
Publication: |
600/442 |
International
Class: |
A61B 008/00 |
Claims
We claim:
1. An ultrasonic system for multiple transmission angle ultrasonic
interrogation in tissues with heterogenous structures that alter
ultrasonic properties, comprising: a) a first ultrasonic transducer
with an axis of transmission in common with a second ultrasonic
transducer, said axis of transmission is through a portion of a
tissue, b) an x, y positioner that engages said first ultrasonic
transducer and said second ultrasonic transducer, said x, y
positioner controllably 1) positions said first ultrasonic
transducer and said second ultrasonic transducer in a desired
manner between at least a first and a second position while
generally maintaining said axis of transmission and 2) establishes
predetermined transmission angles for said first ultrasonic
transducer and said second ultrasonic transducer to interrogate
said portion at multiple transmission angles through heterogenous
structures in said portion, and c) a computational unit designed to
manage ultrasonic signal transmission and reception of said first
ultrasonic transducer and said second ultrasonic transducer with
either BUA or SOS or both and may optionally be designed to control
movement of said x, y positioner; wherein said ultrasonic
measurements with multiple transmission angles are improved
compared to the absence of multiple transmission angles.
2. The ultrasonic system of claim 1, further comprising a z
positioner that positions at least one of said first or second
ultrasonic transducers, and said z positioner changes the distance
of transmission along said axis of transmission between said first
ultrasonic transducer and said second ultrasonic transducer.
3. The ultrasonic system of claim 2, wherein said computational
unit can estimate broadband ultrasonic attenuation at multiple
transmission angles.
4. The ultrasonic system of claim 3, wherein said x, y positioner
can establish at least three predetermined transmission angles.
5. The ultrasonic system of claim 4, wherein said transmission
angles vary overall by at thirty degrees.
6. The ultrasonic system of claim 1, wherein said first transducer
and said second transducer can transmit and receive signals to
change the direction of transmission between said first transducer
and said second transducer to reduce ultrasonic artifacts due to
variations in tissue interposed along the transmission path.
7. The ultrasonic system of claim 6, wherein said x, y positioner
comprises a frame to maintain said axis of transmission between
said first and second ultrasonic transducers, said frame engages an
x track and said x track engages a y track, thereby an operator can
move said first and second ultrasonic transducers manually in
either an x or y dimension or combination thereof with respect to
an anatomical region.
8. The ultrasonic system of claim 7, wherein said x, y positioner
can accommodate an appendage and said appendage is held in a
predetermined position in said ultrasonic system relative to said
x, y positioner.
9. The ultrasonic system of claim 1, wherein said x, y positioner
is automatically controlled by said computational unit.
10. The ultrasonic system of claim 9, wherein said computational
unit comprises a computational program to calculate BUS or SOS or
both at multiple transmission angles.
11. The ultrasonic system of claim 10, wherein said computational
unit is designed to instruct said x, y positioner to position said
first ultrasonic transducer and said second ultrasonic transducer
to interrogate said tissue with respect to an anatomic landmark and
said x,y positioner generally maintains said axis of transmission
between said first ultrasonic transducer and said second ultrasonic
transducer at a preselected set of coordinates in relation to said
anatomic landmark.
12. The ultrasonic system of claim 10, wherein said computational
unit is designed to remove or filter interference or scatter
detected at multiple transmission angles.
13. The ultrasonic system of claim 11, wherein said anatomic
landmark is part of an anatomical region selected from the group
consisting of a knee, an ankle, and tibia, and further wherein said
x, y positioner is adapted to accommodate said anatomical region
and said first ultrasonic transducer and said second ultrasonic
transducer are adapted for interrogation using broadband ultrasonic
attenuation of dense tissue comprising bone.
14. The ultrasonic system of claim 1, wherein said computational
unit can 1) average signals from multiple transmission angles and
2) instruct said x, y positioner to a position over said anatomic
landmark, thereby said first ultrasonic transducer and second
ultrasonic transducer have an axis of transmission generally
through said anatomic landmark.
15. An ultrasonic system for automated ultrasonic measurements at
multiple transmission angles, comprising: a) an ultrasonic
transducer unit comprising 1) an ultrasonic transducer that can
transmit and receive signals and 2) a multiple transmission angle
positioner to vary the transmission angle of said ultrasonic
transducer with respect to the plane of a tissue in a predetermined
fashion and with necessarily changing the general position of said
ultrasonic transducer with respect to said tissue, and b) a
computational unit designed to manage ultrasonic signal
transmission and reception of said ultrasonic transducer unit and
to process signals from said ultrasonic transducer unit using
multiple transmission angles.
16. The ultrasonic system of claim 15, wherein said computational
unit is designed to average ultrasonic signals received from said
ultrasonic transducer unit using multiple transmission angles.
17. The ultrasonic system of claim 15, wherein said computational
unit is further designed to process received ultrasonic signals
from said ultrasonic transducer to generate at least one data set
of an ultrasonic property determined at predetermined, multiple
transmission angles.
18. The ultrasonic system of claim 17, wherein said ultrasonic
property is selected from the group consisting of broadband
ultrasonic attenuation, echogenicity, reflective surfaces,
distances from said transducer unit, speed of sound, ultrasonic
images, and Doppler information.
19. The ultrasonic system of claim 18, wherein said computational
unit is further designed to compare ultrasonic signals at
predetermined, multiple transmission angles to determine artifact
pattern(s) or location(s) of anatomical structures.
20. The ultrasonic system of claim 16, wherein said computational
unit directs a positioning unit to position said transducer unit
with reference to an anatomical landmark.
21. The ultrasonic system of claim 20, wherein said computational
unit is designed to instruct said transducer unit to transmit and
receive signals after positioning said transducer unit with respect
to said anatomical landmark.
22. The ultrasonic system of claim 17, wherein said computational
unit further comprises a display for showing ultrasonic properties
as a function of predetermined, multiple transmission angles.
23. The ultrasonic system of claim 17, wherein said ultrasonic
system further comprises a positioning unit for changing the
spatial relationship between an anatomic landmark in an anatomical
region and said ultrasonic transducer unit, thereby permitting
interrogation with reference to said anatomic landmark in said
anatomical region by positioning said transducer unit with respect
to said anatomical landmark.
24. The ultrasonic system of claim 15, wherein said multiple
transmission angle positioner is not a C arm unit or can be engaged
in frame that offers multiple position at different anatomical
regions.
25. The ultrasonic system of claim 15, wherein said multiple
transmission angle positioner maintains said ultrasonic transducer
unit in substantially the same anatomical region while varying
transmission angles of said ultrasonic transducer unit
positioner.
26. The ultrasonic system of claim 23, wherein said system is
adapted for an ankle.
27. An ultrasonic system for tissue ultrasonic interrogation for
broadband ultrasonic attenuation, comprising: a) a first ultrasonic
transducer with an axis of transmission through an anatomical
region to be interrogated and said first ultrasonic transducer is
adapted for BUA, b) a second ultrasonic transducer with said axis
of transmission through said anatomical region to be interrogated
and adapted for BUA, wherein monitoring broadband ultrasonic
attenuation between said first ultrasonic transducer and said
second ultrasonic transducer is permitted, c) a positioning unit to
vary the transmission angle of the axis of transmission with
respect to said, and d) a computational unit designed to manage
ultrasonic signal transmission of said first ultrasonic transducer,
to manage ultrasonic signal reception of said second ultrasonic
transducer and to control the transmission angle of the axis of
transmission.
28. The ultrasonic system of claim 27, wherein said positioning
unit comprises an x,y positioner for said first ultrasonic
transducer and said second ultrasonic transducer at can establish
at least 3 predetermined transmission angles.
29. The ultrasonic system of claim 27, wherein said x,y positioner
is designed to position said first ultrasonic transducer and said
second ultrasonic transducer, wherein said first axis of
transmission at each transmission angle generally passes through
the same anatomical region that is no more than about 5 to 8 cm
squared.
30. The ultrasonic system of claim 28, wherein said computational
unit comprises a program to generate an anatomic landmark at
multiple transmission angles and said positioning unit comprises a
z positioner controlled by said computational unit.
31. An ultrasonic method for ultrasonic interrogation, comprising:
a) positioning, with respect to an anatomical region suspected of
having tissue heterogenity that causes variations in acoustic
properties, an ultrasonic transducer unit comprising either 1) a
first ultrasonic transducer that can transmit and receive signals
or 2) a pair of ultrasonic transducers where a first member of said
pair is designed to transmit signals and a second member of said
pair is designed to receive signals, b) interrogating said
anatomical region with said ultrasonic transducer unit at
predetermined, multiple transmission angles, and c) recording an
ultrasonic property of said anatomical region, and d) storing said
ultrasonic property in a storage device.
32. The ultrasonic method of claim 31, further comprising the steps
of comparing ultrasonic signals at different predetermined,
multiple transmission angles.
33. The ultrasonic method of claim 31, wherein steps a, b, and c
are repeated and each positioning step is performed in relation to
an anatomic landmark.
34. The ultrasonic method of claim 33, wherein said positioning
steps are performed to generate an axis of transmission
substantially through said anatomic landmark.
35. The ultrasonic method of claim 34, wherein said positioning
steps are performed in relation to a reference anatomic landmark of
said anatomical region stored in retrievable form in a storage
device.
36. An ultrasonic method for determining broadband ultrasonic
attenuation or speed of sound measurements in dense tissues,
comprising: a) interrogating a tissue at predetermined, multiple
transmission angles with an ultrasonic transducer unit adapted for
either 1) broadband ultrasonic attenuation or 2) speed of sound
measurements or both, b) determining dense tissue broadband
ultrasonic attenuation, dense tissue speed of sound or both at two
or more predetermined, multiple transmission angles, wherein said
determining step generates a dense tissue broadband ultrasonic
attenuation value, dense tissue speed of sound value or both that
is more indicative of broadband ultrasonic attenuation or speed of
sound in dense tissue than interrogation in the absence of
predetermined, multiple transmission angles.
37. The ultrasonic method of claim 36, wherein said determining
step further comprises determining either 1) broadband ultrasonic
attenuation or 2) speed of sound in said tissue or both at five or
more predetermined transmission angles.
38. The ultrasonic method of claim 36, wherein said determining
step further comprises adjusting either 1) broadband ultrasonic
attenuation, 2) speed of sound in said tissue or 3) both for
differences in the transmission path at two or more predetermined
transmission angles.
39. The ultrasonic method of claim 36, wherein said tissue
comprises a heel.
40. The ultrasonic method of claim 39, wherein said determining
step further comprises calculating speed of sound for transmission
in at least two different transmission directions.
41. An ultrasonic method for generating an anatomic landmark for
ultrasonic interrogation of an anatomical region, comprising: a)
positioning, if necessary, on the surface of a patient, with
respect to an anatomical region, an ultrasonic transducer unit
comprising either 1) a first ultrasonic transducer that can
transmit and receive signals or 2) a pair of ultrasonic transducers
wherein a first member of said pair is designed to transmit signals
and a second member of said pair is designed to receive signals,
and b) interrogating said anatomical region with said ultrasonic
transducer unit at a first transmission angle, c) interrogating
said anatomical region with said ultrasonic transducer unit at a
second transmission angle, d) identifying an anatomic landmark in
common with the signals obtained in steps (b) and (c) in said
anatomical region with an ultrasonic property of said anatomical
region.
42. The ultrasonic method of claim 41, further comprising the step
of storing said anatomic landmark in a storage device, and wherein
positioning is through a positioning unit and said transducer unit
has a plurality of predetermined transmission angles for
interrogation and said second transmission angle increases the
accuracy of said anatomical landmark compared to interrogation with
a single transmission angle.
43. The ultrasonic method of claim 41, wherein said anatomic
landmark was not previously identified in said patient.
44. The ultrasonic method of claim 41, wherein said positioning is
automated and not hand held and steps b through c are repeated
automatically by a computational unit.
45. An ultrasonic method for determining broadband ultrasonic
attenuation or speed of sound measurements in dense tissues,
comprising: a) interrogating a patient's tissue with at least a
first ultrasonic transducer unit at a first transmission angle and
a second ultrasonic transducer unit at a second transmission angle,
wherein said first ultrasonic transducer unit and said second
ultrasonic transducer unit are a) adapted for either 1) broadband
ultrasonic attenuation or 2) speed of sound measurements or both
and b) have an angle of least about 150 degrees between said first
ultrasonic transducer unit and said second transducer unit, b)
interrogating said patient's tissue with said first ultrasonic
transducer unit at a third transmission angle and said second
ultrasonic transducer unit a fourth transmission angle while
maintaining an angle of at least about 150 degrees between said
first transducer unit and said second transducer unit, and c)
determining dense tissue broadband ultrasonic attenuation, dense
tissue speed of sound or both for said tissue; wherein said
determining step generates a dense tissue broadband ultrasonic
attenuation value, dense tissue speed of sound value or both that
is more indicative of broadband ultrasonic attenuation or speed of
sound in dense tissue than in the absence of interrogating said
patient's tissue with at least said first ultrasonic transducer
unit at a third transmission angle and said second ultrasonic
transducer unit a fourth transmission angle.
46. The ultrasonic method of claim 45, further comprising the steps
of: d) transmitting ultrasonic pulses into said tissue with said
first ultrasonic transducer unit and receiving ultrasonic signals
with said second ultrasonic transducer unit, and e) correcting
dense tissue broadband ultrasonic attenuation, dense tissue speed
of sound or both for soft tissue acoustic variations, wherein said
correcting step generates a dense tissue broadband ultrasonic
attenuation value, dense tissue speed of sound value or both that
is more indicative of broadband ultrasonic attenuation or speed of
sound in dense tissue than in the absence of correcting for soft
tissue acoustic variations.
47. The ultrasonic method of claim 45, wherein said first
ultrasonic transducer unit and said second ultrasonic transducer
unit have a common axis of transmission in at least one step.
48. The ultrasonic method of claim 47, wherein said first
ultrasonic transducer unit and said second ultrasonic transducer
unit have a common axis of transmission in at least step (a) or (b)
and said first ultrasonic transducer and a said second ultrasonic
transducer unit have a common axis of transmission through an
anatomical region that is non-orthogonal with respect to the tissue
plane by about 5 to 20 degrees.
49. The ultrasonic method of claim 48, wherein said anatomical
region includes the calcaneus.
50. The ultrasonic method of claim 47, wherein said step (a)
includes transmitting ultrasonic waves for a first time duration
and step (b) includes transmitting ultrasonic waves for a second
time duration, wherein difference in said first time duration and
said second time duration is not more than about 1,000 ms.
51. The ultrasonic method of claim 47, wherein said step (e)
includes averaging BUA values obtained from (1) said first and
second transmission angles and (2) said third and fourth
transmission angles and comparing averaged BUA values from (1) with
averaged BUA values from (2) to determine the highest or lowest BUA
value.
52. The ultrasonic method of claim 47, wherein said step (e)
includes averaging SOS values obtained from (1) said first and
second transmission angles and (2) said third and fourth
transmission angles and comparing averaged SOS values from (1) with
averaged SOS values from (2) to determine the highest or lowest SOS
value.
53. The ultrasonic method of claim 47, wherein said first and
second transmission angles are robotically established and (2) said
third and fourth transmission angles are robotically
established.
54. The ultrasonic method of claim 47, wherein said interrogating
in steps (b) and (c) further comprises generating said first and
second transmission angles at a first time point with a means for
generating a transmission angle and generating said third and
fourth transmission angles at a second time point with said means
for generating a transmission angle.
55. The ultrasonic method of claim 54, wherein said first time
point and said second time point are separated by a predetermined
length of time instructed by a computational unit.
56. The ultrasonic method of claim 47, wherein said first and
second transmission angles establish a first common axis of
transmission between said first ultrasonic transducer and said
second ultrasonic transducer and said third and fourth transmission
angles establish a second common axis of transmission between said
first ultrasonic transducer and said second ultrasonic transducer;
further wherein said first common axis of transmission and second
common axis of transmission are generally through a single
interrogation site of an anatomical region and have substantially
more than about a 10 degree difference with respect to a common
plane of said anatomical region.
57. An ultrasonic system for determining broadband ultrasonic
attenuation or speed of sound measurements in a tissue, comprising:
a) a transducer unit comprising at least a first ultrasonic
transducer engaged with a first multiple transmission angle unit to
controllably vary first transmission angles and a second ultrasonic
transducer engaged with a second multiple transmission angle unit
to controllably vary second transmission angles, wherein said first
ultrasonic transducer unit and said second ultrasonic transducer
unit are adapted for either 1) broadband ultrasonic attenuation or
2) speed of sound measurements or both, and b) a computational unit
for controllably adjusting transmission angles of said first and
second transducer; wherein said ultrasonic system will measure
broadband ultrasonic attenuation value, speed of sound value or
both if so desired.
58. An ultrasonic system of claim 57, further comprising an
ultrasonic transducer to determine soft tissue thickness in an
anatomical region and a means for correcting dense tissue broadband
ultrasonic attenuation, dense tissue speed of sound or both for
said soft tissue thickness.
59. A computer program product, comprising: a) instructions for a
positioning unit to vary the transmission angle of a transducer or
plurality of transducers at a plurality of transmission angles in
an anatomical region, b) instructions for interrogating said
anatomical region with said transducer or said plurality of
transducers at said plurality of transmission angles, and c)
instructions for recording at least one ultrasonic property at said
plurality of transmission angles, wherein instructions (a) through
(c) facilitates a clinically relevant measurement and instructions
(a) through (c) are stored on a computer retrievable medium.
60. The computer program product of claim 61, further comprises: f)
instructions for comparing ultrasonic singals at a plurality of
transmission angles.
61. The computer program product of claim 61, wherein said clinical
measurement is BUA or SOS.
62. The computer program product of claim 61, wherein said clinical
measurement is echogencity, reflective surface or ultrasonic image
information.
63. The computer program product of claim 61, wherein said clinical
measurement is tissue and flow information obtained after
administration of ultrasonic contrast agents.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
09/071,854, filed on May 2, 1998, now U.S. Pat. No. 6,585,649,
which is a continuation of application Ser. No. 09/036,940, filed
on Mar. 9, 1998, now U.S. Pat. No. 6,013,031, the contents of each
of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The invention relates to ultrasonic methods, compositions
and devices, particularly methods, compositions and devices that
provide for multiple angle interrogation with ultrasonic
transducer(s) over an anatomical region.
BACKGROUND
[0003] Ultrasonic techniques are often used as methods free of
ionizing radiation for non-invasive assessment of anatomy, such as
skeletal status in patients with osteoporosis. Quantitative aspects
of these ultrasonic techniques can permit assessment of bone mass
and density, as well as bone structure. Ultrasonic techniques for
evaluating skeletal status also include measurements of speed of
sound ("SOS") that reflect the transmission velocity of ultrasonic
waves passing through bone tissue and soft tissue, measurements of
broadband ultrasonic attenuation ("BUA") that assess the frequency
dependence of ultrasonic attenuation, and pulse echo techniques
that measure the energy scattered from the internal structure of
the bone.
[0004] Many different measurement sites have been proposed for
osteoporosis, such as the tibia, the patella, the phalanges, or the
calcaneus. The calcaneus is preferred for quantitative ultrasonic
measurement of skeletal status. It is composed of predominantly
trabecular bone with only a thin cortical bone envelope medially
and laterally, which together provide an excellent medium for
detecting changes in SOS and BUA measurements. The calcaneus also
permits convenient ultrasonic interrogation for the operator and
the patient alike.
[0005] Although a number of commercial devices exist for diagnosis
of osteoporosis, clinicians have recognized the limitations of such
devices and methods. Correlations between quantitative ultrasonic
measurements and assessments of bone mineral density using
quantitative computed tomography, dual x-ray absorptiometry, and
single photon absorptiometry have been reported to be poor at the
calcaneus, as well as at other sites.
[0006] In addition, ultrasonic measurements of tissue, particularly
in the calcaneus, often suffer from heterogenous tissue structures.
Such structures as described herein can interfere with
interrogation, which leads to deceased accuracy and precision of
such measurements.
[0007] Consequently, the inventors have recognized the need, among
other things, to provide reliable ultrasonic devices and accurate,
and qualitative or quantitative methods for ultrasonic measurements
in the diagnosis of osteoporosis, as well as methods and devices to
generally improve diagnostic tools based on ultrasonic
measurements. The methods and devices provided herein permit, among
other things, correction of ultrasonic parameters, such as speed of
sound and broadband ultrasonic attenuation, for soft tissue
structures interposed in the ultrasonic beam and tissue
heterogeneity and variations.
SUMMARY
[0008] While many of the embodiments of the invention will find
particular application in clinical measurements, such as BUA or
SOS, and surgical procedures, such trocar procedures and catheter
procedures, the invention provides for general ultrasonic devices
and methods that will be applicable to many clinical
applications.
[0009] The invention includes an ultrasonic system for multiple
transmission angle ultrasonic interrogation in tissues with
heterogenous structures that alter ultrasonic properties. The
system can comprise a first ultrasonic transducer with an axis of
transmission in common with a second ultrasonic transducer, said
axis of transmission is through a portion of tissue suspected of
having heterogenous structures that alter ultrasonic properties.
The system can include an x, y positioner that can engage the first
ultrasonic transducer and the second ultrasonic transducer. The x,
y positioner controllably 1) positions the first ultrasonic
transducer and the second ultrasonic transducer in a desired manner
between at least a first and a second position while generally
maintaining the axis of transmission and 2) establishes
predetermined transmission angles for the first ultrasonic
transducer and the second ultrasonic transducer to interrogate the
portion of the tissue at multiple transmission angles through
heterogenous structures in the tissue. A computational unit can be
included that is designed to manage ultrasonic signal transmission
and reception of the first ultrasonic transducer and the second
ultrasonic transducer with either BUA or SOS or both. It may
optionally be designed to control movement of the x, y positioner.
The ultrasonic measurements with multiple transmission angles are
typically improved compared to interrogation in the absence of
multiple transmission angles.
[0010] In addition, the invention includes an ultrasonic system for
automated ultrasonic measurements at multiple transmission angles.
The system comprises an ultrasonic transducer unit comprising 1) an
ultrasonic transducer that can transmit and receive signals and 2)
a multiple transmission angle positioner to vary the transmission
angle of the ultrasonic transducer with respect to the plane of a
tissue in a predetermined fashion. Preferably, the transducer unit
is designed to vary the transmission angle without necessarily
changing the general position of the ultrasonic transducer with
respect to the tissue. This allows the substantially same region to
be interrogated at different angles. The system can include a
computational unit designed to manage ultrasonic signal
transmission and reception of the ultrasonic transducer unit and to
process signals from the ultrasonic transducer unit at multiple
transmission angles, for example using signal averaging, filtering
unwanted signals or pattern recognition of desired types of
acoustic signatures. Preferably, the computational unit is designed
to process received ultrasonic signals from the ultrasonic
transducer to generate at least one data set of an ultrasonic
property determined at predetermined, multiple transmission angles.
Such an ultrasonic property can be selected from the group
consisting of broadband ultrasonic attenuation, echogenicity,
reflective surfaces, distances from the transducer unit, speed of
sound, and ultrasonic images.
[0011] In addition, the invention includes an ultrasonic system for
tissue ultrasonic interrogation for broadband ultrasonic
attenuation at multiple transmission angles. The system comprises a
first ultrasonic transducer with an axis of transmission through an
anatomical region to be interrogated and the first ultrasonic
transducer is adapted for BUA and a second ultrasonic transducer
adapted for BUA with the axis of transmission through the
anatomical region to be interrogated, wherein monitoring broadband
ultrasonic attenuation between the first ultrasonic transducer and
the second ultrasonic transducer is permitted. The system includes
a positioning unit to vary the transmission angle of the axis of
transmission with respect to the tissue plane. The system may have
a computational unit designed to manage ultrasonic signal
transmission of the first ultrasonic transducer, to manage
ultrasonic signal reception of the second ultrasonic transducer and
to control the transmission angle of the axis of transmission.
Typically, the positioning unit comprises an x,y positioner for the
first ultrasonic transducer and the second ultrasonic transducer
that can establish at least 3 predetermined transmission angles
while maintaining a common axis of transmission. Preferably, the
x,y positioner is designed to position the first ultrasonic
transducer and the second ultrasonic transducer with first axis of
transmission at each transmission angle generally passing through
the same anatomical region. Typically, the center of axis of
transmission at each angle passes through an area of the anatomical
region that is no more than about 5 to 8 cm squared.
[0012] The invention also includes an ultrasonic method for
ultrasonic interrogation at multiple transmission angles. The
method comprises positioning, with respect to an anatomical region,
an ultrasonic transducer unit comprising either 1) a first
ultrasonic transducer that can transmit and receive signals or 2) a
pair of ultrasonic transducers where a first member of the pair is
designed to transmit signals and a second member of the pair is
designed to receive signals. The methods includes interrogating the
anatomical region with the ultrasonic transducer unit at
predetermined, multiple transmission angles, and recording an
ultrasonic property of the anatomical region. The method further
comprises storing the ultrasonic property in a storage device.
[0013] The invention also includes an ultrasonic method for
determining broadband ultrasonic attenuation or speed of sound
measurements in dense tissues. The method comprises intrrogating a
tissue at predetermined, multiple tranmission angles with an
ultrasonic transducer unit adapted for either 1) broadband
ultrasonic attenuation or 2) speed of sound measurements or both.
The method includes determining dense tissue broadband ultrasonic
attenuation, dense tissue speed of sound or both at two or more
predetermined, multiple transmission angles, wherein the
determining step generates a dense tissue broadband ultrasonic
attenuation value, dense tissue speed of sound value or both that
is more indicative of broadband ultrasonic attenuation or speed of
sound in dense tissue than interrogation in the absence of
predetermined, multiple transmission angles.
[0014] The invention also includes an ultrasonic method for
generating an anatomic landmark for ultrasonic interrogation of an
anatomical region, comprising:
[0015] positioning, if necessary, on the surface of a patient, with
respect to an anatomical region, an ultrasonic transducer unit
comprising either 1) a first ultrasonic transducer that can
transmit and receive signals or 2) a pair of ultrasonic transducers
wherein a first member of the pair is designed to transmit signals
and a second member of the pair is designed to receive signals,
and
[0016] interrogating the anatomical region with the ultrasonic
transducer unit at a first transmission angle,
[0017] interrogating the anatomical region with the ultrasonic
transducer unit at a second transmission angle,
[0018] identifying an anatomic landmark in common with the signals
obtained in the above steps in the anatomical region with an
ultrasonic property of the anatomical region.
[0019] The invention also includes an ultrasonic method for
determining broadband ultrasonic attenuation or speed of sound
measurements in dense tissues, comprising:
[0020] interrogating a patient's tissue with at least a first
ultrasonic transducer unit at a first transmission angle and a
second ultrasonic transducer unit at a second transmission angle,
wherein said first ultrasonic transducer unit and said second
ultrasonic transducer unit are a) adapted for either 1) broadband
ultrasonic attenuation or 2) speed of sound measurements or both
and b) have an angle of least about 150 degrees between said first
ultrasonic transducer unit and said second transducer unit,
[0021] interrogating said patient's tissue with said first
ultrasonic transducer unit at a third transmission angle and said
second ultrasonic transducer unit at a fourth transmission angle
while maintaining an angle of at least about 150 degrees between
said first transducer unit and said second transducer unit, and
[0022] determining dense tissue broadband ultrasonic attenuation,
dense tissue speed of sound or both for said tissue; wherein said
determining step generates a dense tissue broadband ultrasonic
attenuation value, dense tissue speed of sound value or both that
is more indicative of broadband ultrasonic attenuation or speed of
sound in dense tissue than in the absence of interrogating said
patient's tissue with at least said first ultrasonic transducer
unit at a third transmission angle and said second ultrasonic
transducer unit at a fourth transmission angle.
[0023] The invention also includes an ultrasonic system for
determining broadband ultrasonic attenuation or speed of sound
measurements in a tissue, comprising:
[0024] a transducer unit comprising at least a first ultrasonic
transducer engaged with a first multiple transmission angle unit to
controllably vary first transmission angles and a second ultrasonic
transducer engaged with a second multiple transmission angle unit
to controllably vary second transmission angles, wherein the first
ultrasonic transducer unit and the second ultrasonic transducer
unit are adapted for either 1) broadband ultrasonic attenuation or
2) speed of sound measurements or both, and
[0025] a computational unit for controllably adjusting transmission
angles of the first and second transducer; wherein the ultrasonic
system will measure broadband ultrasonic attenuation value, speed
of sound value or both if so desired.
[0026] The invention also includes a computer program product,
comprising:
[0027] instructions for a positioning unit to vary the transmission
angle of a transducer or plurality of transducers at a plurality of
transmission angles in an anatomical region,
[0028] instructions for interrogating the anatomical region with
the transducer or the plurality of transducers at the plurality of
transmission angles, and
[0029] instructions for recording at least one ultrasonic property
at the plurality of transmission angles, wherein the above
instructions facilitates a clinically relevant measurement and such
instructions are stored on a computer retrievable medium.
BRIEF DESCRIPTION OF FIGURES
[0030] FIG. 1A and FIG. 1B show a tissue interrogated by an
ultrasonic transducer (140; T) that transmits to an ultrasonic
receiver (150; R) (or detector) at different transmission angles
and with different axes of transmission. The axis of transmission
is shown as .alpha. (or .beta.) and has a transmission path from T
to R.
[0031] FIG. 1C and FIG. 1D show the same tissue as FIG. 1A and FIG.
1B in a different physiological state that changes the dimensions
of the tissue and its underlying structure. The tissue is
interrogated by an ultrasonic transducer (140; T) that transmits to
an ultrasonic receiver (150; R) (or detector) at different
transmission angles and with different axes of transmission as in
FIG. 1C and FIG. 1D. The axis of transmission is shown as .alpha.
(or .beta.) and has a transmission path from T to R.
[0032] FIG. 1E shows received signals in such tissue in different
physiological states and at different transmission angles.
[0033] FIG. 2A shows an example of a typical prior art device for
measuring the speed of sound or broadband ultrasonic attenuation in
a healthy non-edematous patient.
[0034] FIG. 2B shows an example of a typical prior art device for
measuring the speed of sound or broadband ultrasonic attenuation in
a patient with peripheral edema. Edema increases the thickness of
the soft tissue inferior and posterior to the calcaneus.
[0035] FIG. 3A shows another embodiment of the invention comprising
two ultrasonic transducers 300 attached to an x-positioner 310 and
a y-positioner 320. The heel 330 and the calcaneus 340 are seated
on a foot holder 350. The ultrasonic transducer 300 is brought in
contact with the heel 330 using a z-positioner member 360 that can
move in and out of a frame 370 continuously or in a stepwise
fashion. The ultrasonic transmission axis 380 is also shown.
[0036] FIG. 3B is a side view of the ultrasonic transducer (T) 300,
the x-positioner 310, and the y-positioner 320 shown in FIG. 3A
showing the tracks of each postioner. Typically, one positioner
will engage the other positioner to permit x, y movement either
concurrently (moving in both directions simultaneously) or
sequentially (moving in one dimension first and then in a second
dimension).
[0037] FIG. 3C shows another embodiment of the invention. The
ultrasonic transducers 300 are attached to a positioning system 390
that affords movement of the transducers in x, y-, and z-direction,
as well as angulation of the transducers 300 and the resultant
ultrasonic transmission axis 380. The angulation position of the
transducers 300 and the ultrasonic transmission axis 380 is
substantially zero.
[0038] FIG. 3D shows the ultrasonic transducers 300 attached to a
positioning system 390 that affords movement of the transducers in
x, y-, and z-direction, as well as angulation of the transducers
300 and the resultant ultrasonic transmission axis 380. The
angulation position of the transducers 300 and the ultrasonic
transmission axis 380 is substantially different from zero.
[0039] FIG. 3E shows an expanded view of the embodiment presented
in FIGS. 3A-D. The ultrasonic transducer 300 is attached to a
positioning system 390 that affords movement of the transducers in
x, y-, and z-direction, as well as angulation of the transducers
300. The ultrasonic beam 395 has substantially zero angulation.
[0040] FIG. 3F shows an expanded view of the positioning system 390
and the ultrasonic transducers 300 with inferior angulation of the
ultrasonic beam 395.
[0041] FIG. 3G shows a magnification view of the positioning system
390 and the ultrasonic transducers 300 with superior angulation of
the ultrasonic beam 395.
DETAILED DESCRIPTION OF THE INVENTION
1.0 Abbreviations and Definitions
[0042] ABBREVIATIONS include broadband ultrasonic attenuation (BUA)
and speed of sound (SOS).
[0043] Acoustic communication refers to the passage of ultrasonic
waves between two points in a predetermined manner. Usually, this
is accomplished by selecting a desired pathway between the two
points that permits the passage of ultrasonic waves either directly
or indirectly. Direct passage of ultrasonic waves would occur, for
instance, when an ultrasonic crystal is directly disposed to
(usually touching) an acoustic coupling material, such as a
composite. Indirect passage of ultrasonic waves would occur, for
instance, when an ultrasonic crystal is located at a predetermined
distance from an acoustic coupling material or when a number of
acoustic coupling materials, often heterogenous materials, form two
or more layers.
[0044] Acoustic coupler refers to a connection or plurality of
connections between an ultrasonic crystal and a substance that
reflects or passes ultrasonic pulses and is not part of the device
or object being interrogated. The acoustic coupler will permit
passage of ultrasonic waves. It is desirable for such couplers to
minimize attenuation of ultrasonic pulses or signals and to
minimize changes in the physical properties of an ultrasonic wave,
such as wave amplitude, frequency, shape and wavelength. Typically,
an ultrasonic coupler will either comprise a gel or other
substantially soft material, such as a pliable polymer matrix, that
can transmit ultrasonic pulses.
[0045] Acoustic coupling material is a material that passes
ultrasonic waves, usually from a probe to a subject or tissue to be
interrogated it is usually not a living material and is most often
a polymer or gel or acoustic coupler.
[0046] Acoustic mirror refers to a device that can reflect an
ultrasonic wave and redirect the ultrasonic wave in a predetermined
manner. If the original ultrasonic waves are transmitted at an
angle .alpha., which is measured relative to the surface of the
plane of the acoustic mirror, the reflected ultrasonic waves can be
oriented at an angle .alpha.'=180.degree.-.alpha. relative to the
plane of the acoustic mirror. An acoustic mirror(s) can be used in
an ultrasonic system to vary the transmission angle.
[0047] Anatomical region refers to a site on the surface of the
skin, tumor, organ or other definable biomass that can be
identified by an anatomical feature(s) or location. Anatomical
region can include the biomass underlying the surface. Usually,
such a region will be definable according to standard medical
reference methodology, such as that found in Williams et al.,
Gray's Anatomy, 1980.
[0048] BUA means broadband ultrasonic attenuation and when measured
a BUA value is expressed as dB/MHz. Note that actual attenuation of
broadband ultrasonic waves increases as soft tissue thickness
increases, while BUA values (dB/MHz) decrease as soft tissue
thickness increases. This distinction is often not recognized in
the literature, which leads to misleading or potentially misleading
conclusions about the effect of soft tissue on actual attenuation
of broadband ultrasonic waves and BUA values.
[0049] A--scan refers to an ultrasonic technique where an
ultrasonic source transmits an ultrasonic wave into an object, such
as a patient's body, and the amplitude of the returning echoes
(signals) are recorded as a function of time. Structures that lie
along the direction of propagation are interrogated. As echoes
return from interfaces within the object or tissue, the transducer
crystal produces a voltage that is proportional to the echo
intensity. The sequence of signal acquisition and processing of
A--scan data in a modern ultrasonic instrument usually occurs in
six major steps:
[0050] Detection of the echo (signal) occurs via mechanical
deformation of the piezoelectric crystal and is converted to an
electric signal having a small voltage.
[0051] Preamplification of the electronic signal from the crystal,
into a more useful range of voltages is usually necessary to ensure
appropriate signal processing.
[0052] Time Gain Compensation compensates for the attenuation of
the ultrasonic signal with time, which arises from travel distance.
Time gain compensation may be user-adjustable and may be changed to
meet the needs of the specific application. Usually, the ideal time
gain compensation curve corrects the signal for the depth of the
reflective boundary. Time gain compensation works by increasing the
amplification factor of the signal as a function of time after the
ultrasonic pulse has been emitted. Thus, reflective boundaries
having equal abilities to reflect ultrasonic waves will have equal
ultrasonic signals, regardless of the depth of the boundary.
[0053] Compression of the time compensated signal can be
accomplished using logarithmic amplification to reduce the large
dynamic range (range of smallest to largest signals) of the echo
amplitudes. Small signals are made larger and large signals are
made smaller. This step provides a convenient scale for display of
the amplitude variations on the limited gray scale range of a
monitor.
[0054] Rectification, demodulation and envelope detection of the
high frequency electronic signal permits the sampling and
digitization of the echo amplitude free of variations induced by
the sinusoidal nature of the waveform.
[0055] Rejection level adjustment sets the threshold of signal
amplitudes that are permitted to enter a data storage, processing
or display system. Rejection of lower signal amplitudes reduces
noise levels from scattered ultrasonic signals.
[0056] B--scan refers to an ultrasonic technique where the
amplitude of the detected returning echo is recorded as a function
of the transmission time, the relative location of the detector in
the probe and the signal amplitude. This is often represented by
the brightness of a visual element, such as a pixel, in a
two-dimensional image. The position of the pixel along the y-axis
represents the depth, i.e. half the time for the echo to return to
the transducer (for one half of the distance traveled). The
position along the x-axis represents the location of the returning
echoes relative to the long axis of the transducer, i.e. the
location of the pixel either in a superoinferior or mediolateral
direction or a combination of both. The display of multiple
adjacent scan lines creates a composite two-dimensional image that
portrays the general contour of internal organs.
[0057] Chip refers to any current and future electronic hardware
device that can be used in a computational unit and can be used as
an aid in controlling the components of an ultrasonic unit
including: 1) timing and synchronizing trigger pulses and
subsequent transmission of ultrasonic waves, 2) measuring and
analyzing incoming ultrasonic signals, 3) comparing data to
predetermined standards and data cut-offs (e.g. electronic
filtering), and 4) performing multiple other simple and complex
calculations. Typically, a chip is silicon-based, micro-electronic
ciruit.
[0058] Computational unit refers to any current or future hardware,
software (e.g. computer program), chip or other device used for
calculations or for providing instructions now developed or
developed in the future. The computational unit may be used for
controlling the ultrasonic generator or source, for defining or
varying the firing rate and pulse repetition rate (as well as other
parameters related to the ultrasonic generator or source), for
measuring the reflected signal, for image reconstruction in B-scan
mode and for filtering and thresholding of the ultrasonic signal.
Other applications of the computational unit to the methods and
devices described herein will be recognized by those skilled in the
art. The computational unit may be used for any other application
related to this technology that may be facilitated with use of
computer software or hardware. The computational unit may comprise
a computer program product with instructions to control the
ultrasonic system. Such computer program products may be stored in
storage devices, such as hard drives, floppy discs, electronic
storage devices or any other storage device capable of relible
storage and retrieval of information (including electronic
signals).
[0059] Detector refers to any structure capable of measuring an
ultrasonic wave or pulse, currently known or developed in the
future. Crystals containing dipoles are typically used to measure
ultrasonic waves. Crystals, such as piezoelectric crystals, shift
in dipole orientation in response to an applied electric current.
If the applied electric current fluctuates, the crystals vibrate to
cause an ultrasonic wave in a medium. Conversely, crystals vibrate
in response to an ultrasonic wave that mechanically deforms the
crystals, which changes dipole alignment within the crystal. This,
in turn, changes the charge distribution to generate an electric
current across a crystal's surface. Electrodes connected to
electronic circuitry sense a potential difference across the
crystal in relation to the incident mechanical pressure. A
transducer can be a detector.
[0060] Echogenicity refers to the brightness of a tissue in an
ultrasonic image relative to the adjacent tissues, typically on a
B-scan image. Echogenicity is dependent on the amount of ultrasonic
waves reflected by the tissue. Certain tissues are more echogenic
than other tissues. Fatty tissue, for example, is more echogenic
than muscle tissue. For identical imaging parameters, fatty tissue
will thus appear brighter than muscle tissue. Consequently, image
brightness can be used to identify different tissues.
[0061] Frame time, when used in the context of positioning an
ultrasonic source, refers to the time that is required to move an
ultrasonic source from a first to a second position (or other
additional positions) and back using a mechanical motor or other
current and future devices. Frame time typically ranges from 10 ms
to 2,000 ms.
[0062] Linear array refers to a transducer design where the
crystals are arranged in a linear fashion along one or more axes.
Crystals can be fired in sequential, as well as non-sequential and
simultaneous firing patterns or a combination thereof. With
sequential firing, each crystal can produce an ultrasonic beam and
receive a returning echo for data collection. The number of
crystals in one array usually determines the number of lines of
sight for each recording. With segmental firing, a group or segment
of crystals can be activated simultaneously resulting in a deeper
near field and a less divergent far field compared with sequential
activation. A segmental linear array produces, however, a smaller
number of lines of sight when compared to a sequential linear array
with the same number of crystals.
[0063] Mechanically connected refers to a connection between two or
more mechanical components, such as an ultrasonic source having at
least two transmission positions. A mechanical connection between
two transmission positions may be accomplished using a mechanical
motor to rotate or move an ultrasonic source. Optionally, the
ultrasonic source can be rotated or moved on a track to vary the
transmission angle.
[0064] Mechanical motor refers to any device that can move a
device, such as the ultrasonic source, from at least a first to a
second position and, if desired, to additional positions. A
mechanical motor may employ a spring-like mechanism to move the
ultrasonic source from the first to the second position. A
mechanical motor may also employ a hydraulic, a magnetic, an
electromagnetic mechanism or any other current and future mechanism
that is capable of moving the ultrasonic source from a first to a
second position.
[0065] Programmed mechanical motor refers to any motor controlled
by a program, such as a program in a chip or computer. Such motors
include mechanical, electrical or hydraulic devices to move an
ultrasonic source from a first to a second position, and if desired
to additional positions. The program usually defines the frame time
that the mechanical motor moves the ultrasonic source from a first
to a second position and back. If more than two positions are used,
the program can move the ultrasonic source to many different
positions, as desired.
[0066] Oscillate refers to moving the ultrasonic source
repetitively from a first to a second position or other additional
positions and moving it back from the second position or other
additional positions. Oscillating from the first to the second
position and back may be achieved using a mechanical motor.
Typically, transducers will be oscillated to vary the transmission
angle.
[0067] Osteoporosis refers to a condition characterized by low bone
mass and microarchitectural deterioration of bone tissue, with a
consequent increase of bone fragility and susceptibility to
fracture. Osteoporosis presents most commonly with vertebral
fractures due to the decrease in bone mineral density and
deterioration of structural properties of the bone. The most severe
complication is hip fracture due to its high morbidity and
mortality.
[0068] Plane refers to the surface of a cross-sectional area of
tissue interrogated by an ultrasonic probe. In ultrasonic
measurements, the portion of the tissue included in the measurement
or image is more accurately referred to as a volume. The
x-dimension of this volume reflects the length of the tissue plane,
i.e. the length of imaged tissue. The x-dimension typically varies
between 1 and 10 cm or more. The y-dimension of this volume
reflects tissue depth from the plane, e.g. the distance from the
skin surface to a reflection point in the tissue. Interrogation of
the y-dimension (or depth of the interrogation) depends, among
other things, on the type of transducer, the type of tissue, and
the frequency with which the ultrasonic beam is transmitted. With
higher frequencies, tissue penetration decreases and the maximum
depth from the tissue plane will decrease. The y-dimension
typically varies between 1 and 30 cm. The z-dimension corresponds
to the width of the plane that is interrogated. It typically varies
between 1 and 15-20 mm. It is understood that such dimensions are
in reference to ultrasonic signals and interrogation. In addition,
x, y, and z dimensions are also used with different meaning in the
context of positioning probes, and devices for locating probes in
different areas of an anatomical region.
[0069] Transmission angle refers to the angle of an ultrasonic beam
that intersects the object or tissue plane. The transmission angle
is normally measured with respect to the object or tissue plane.
The object or tissue plane has a reference angle of zero degrees.
For example, as the transmission angle increases toward 90 degrees
relative to the tissue plane, the ultrasonic beam approaches an
orthogonal position relative to the tissue plane. Preferably,
ultrasonic measurements are initiated when the ultrasonic beam is
orthogonal to the plane of the tissue. Typically, the transmission
angle is varied in a predetermined and controllable manner in order
to interrogate anatomical region as a function of a preselected
transmission angle(s). Varying the transmission angle is
particularly useful for ultrasonic methods used for BUA and SOS
measurements. Transmission angle can be varied by changing the
position of a transducer with respect to the object to be
interrogated.
[0070] First position refers to a position of an ultrasonic source
(or transducer) that detects or transmits an ultrasonic signal or
pulse, respectively. Typically, the first position will have a
predetermined transmission angle associated with it (e.g. 90, 80,
70 or 60 degrees). BUA and SOS can also be measured at the first
position and if desired compared with measurements from other
positions, particularly positions that vary the transmission
angle.
[0071] Second position refers to a position of an ultrasonic source
(or transducer) that transmits or detects an ultrasonic pulse or
signal, respectively and having either a different transmission
angle from the first position or a different anatomical location
than the first position. It is understood that the second position
may have the same anatomical location as the first position while
having a different transmission angle compared to the first
position. Typically, the first position will have a predetermined
transmission angle associated with it (e.g. 90, 80, 70 or 60
degrees). BUA and SOS can also be measured at the second position
and if desired compared with measurements from other positions. In
some applications it will be desirable for the first and second
positions to generally have the same anatomical location while
varying the transmission angle. Additional positions can be readily
achieved by relocating the ultrasonic source to either vary the
anatomical location of interrogation or the transmission angle.
[0072] Transmission frequency refers to the frequency of the
ultrasonic wave that is being transmitted from the ultrasonic
source. Transmission frequency typically ranges between 0.2 MHz and
25 MHz. Higher frequencies usually provide higher spatial
resolution. Tissue penetration decreases with higher frequencies.
Lower transmission frequencies are generally characterized by lower
spatial resolution with improved tissue penetration.
[0073] Ultrasonic pulse refers to any ultrasonic wave transmitted
by an ultrasonic source. Typically, the pulse will have a
predetermined amplitude, frequency, and wave shape. Ultrasonic
pulses may range in frequency between 20 kHz and 20 Mhz or higher.
Ultrasonic pulses may consist of sine waves with single frequency
or varying frequencies, as well as single amplitudes and varying
amplitudes. In addition to sine waves, square waves or any other
wave pattern may be employed. Square waves may be obtained by
adding single-frequency sine waves to other sine waves. The
summation of waves can then result in a square wave pattern.
[0074] Ultrasonic signal refers to any ultrasonic wave measured by
an ultrasonic detector after it has been reflected from the
interface of an object or tissue. Ultrasonic signals may range in
frequency between 20 kHz and 20 Mhz or higher.
[0075] Ultrasonic source refers to any structure capable of
generating an ultrasonic wave or pulse, currently known or
developed in the future. Crystals containing dipoles are typically
used to generate an ultrasonic wave above 20 khz. Crystals, such as
piezoelectric crystals, that vibrate in response to an electric
current applied to the crystal can be used as an ultrasonic source.
In some ultrasonic generators, multiple ultrasonic sources may be
arranged in a linear fashion. This arrangement of ultrasonic
sources is also referred to as a linear array. With linear arrays,
ultrasonic sources are typically fired sequentially, although
simultaneous firing of groups of adjacent ultrasonic sources or
other firing patterns of individual or groups of ultrasonic sources
with various time delays can be achieved as described herein or
developed in the art. The time delay between individual or group
firings can be used to vary the depth of the beam in an object.
[0076] Ultrasonic wave refers to either an ultrasonic signal or
pulse.
2.0 Introduction
[0077] The present invention recognizes for the first time that
errors arising from heterogenous tissue structure in ultrasonic
measurements of speed of sound and broadband ultrasonic attenuation
of trabecular and cortical bone can be reduced or corrected by
measuring BUA or SOS at different transmission angles. Previously,
it was not recognized that ultrasonic measurements at predetermined
transmission angles can be used to correct measured SOS and BUA
values for errors introduced by overlying soft tissues. Nor was it
recognized that tissue heterogenity is a potential source of
decreased accuracy and reproducibility of SOS and BUA measurements
in patients with peripheral edema undergoing diuretic or other
types of medical treatment of edema with resultant fluctuations in
tissue heterogenity. The present invention includes measuring BUA
and SOS using various transmission angles to reduce artifacts
imposed by variations in tissue structure that can affect BUA and
SOS measurements. The present invention also includes applying
appropriate corrections to SOS and BUA based on ultrasonic
measurements at predetermined, multiple transmission angles.
[0078] Without limiting aspects of the invention to a particular
mechanism of action, the inventors believe that the poor
correlations between quantitative ultrasonic techniques and other
methods for assessing bone mineral density are often caused by
structural variations in the interrogated tissue (including the
interrogated bone) with respect to the position of the ultrasonic
transducers. Sources of such interrogation artifacts include
variations in the thickness of the posterior or inferior heel pads,
variations in water content, variations in extracellular matrix
density or content (e.g. protein), variations in soft-tissue
organization, variations in cortical bone density or structure, and
variations in trabecular bone density or structure. Such variations
in tissue structure can affect transmission of ultrasonic waves or
pulses from the transmitter to the detector in other tissues as
well. Ultrasonic measurements of the tissue can also vary even if
the transducer is reproducibly located at an interrogation site
because ultrasonic transmission through the tissue's structure may
change as a function of position or transmission angle. In all
cases, differences in the tissue structures interposed in the
ultrasonic beam path can ultimately change the speed of sound and
broadband ultrasonic attenuation as well as other ultrasonic
properties.
[0079] In addition, interrogation artifacts in SOS and BUA
measurements are particularly pronounced in patients with
abnormally increased soft tissue thickness that is commonly
encountered in patients suffering from peripheral edema due to
cardiovascular, renal, or hepatic disorders. Previous work failed
to recognize that soft tissue swelling or fluctuations in soft
tissue thickness in patients with peripheral edema changes the
acoustic properties of the interrogated tissue. The inventors were
the first to recognize that changes in ultrasonic properties of
interrogated tissue induced by local or generalized soft tissue
swelling or fluctuations in soft tissue physiology can reduce
short-term and long-term in vivo precision of SOS and BUA
measurements. The inventors were also the first to recognize that
soft tissue swelling induced changes in ultrasonic properties of
interrogated tissue overlying bone can be particularly significant
in patients with edema undergoing diuretic or other types of
medical treatment of edema with resultant fluctuations in soft
tissue physiology or homeostasis.
[0080] For example, FIG. 1A through FIG. 1D illustrate tissue
structure variations that can lead to acoustic variations in
ultrasonic measurements due to changes in the interrogation path.
Three types of tissue structure variations are present in such
figures: 1) soft tissue structure heterogenity (as shown FIG. 1A
through FIG. 1D), 2) dense tissue heterogenity (compare for example
FIG. 1A with FIG. 1C) and 3) tissue structure variations due to
changes in the physiology of the tissue (compare FIG. 1A with FIG.
1C).
[0081] FIG. 1A and FIG. 1B show a tissue interrogated by an
ultrasonic transducer (140; T) that transmits to an ultrasonic
receiver (150; R) (or detector) at different transmission angles
and with different axes of transmission. The axis of transmission
is shown as .alpha. (or .beta.) and has a transmission path from T
to R. The transmission path passes through the tissue comprising
skin (100), soft tissue (represented as white), locations of
organized biomaterial (110) with acoustic properties different from
that of the extracellular fluid in the soft tissue (e.g.
differences in echogenicity, scatter, SOS, BUA, or reflection),
amorphous, insoluble biomaterial deposits (120) with acoustic
properties different from that of the extracellular fluid in the
soft tissue (e.g. differences in echogenicity, scatter, SOS, BUA,
or reflection), and dense tissue (130) with acoustic properties
different from that of the extracellular fluid in the soft tissue.
Comparison of the transmission paths of FIG. 1A and FIG. 1B shows
that the transmission path traverses tissue structures with
different acoustic properties. Hence, the ultrasonic measurements,
such as the BUA or SOS, will not be the same depending on the
transmission path, which can be changed by either varying the
transmission angle or the axis of transmission in an anatomical
region.
[0082] In addition, the transmission path from R to T traverses
tissue structures with different acoustic properties in a spatial
or time order that is different from the transmission path from T
to R. Hence, the ultrasonic measurements, such as the BUA or SOS,
will not be the same depending on the direction of the transmission
path, which can be changed by either varying the direction of
transmission in an anatomical region from T to R or from R to
T.
[0083] FIG. 1C and FIG. 1D show the same tissue as FIG. 1A and FIG.
1B in a different physiological state that changes the dimensions
of the tissue and its underlying structure. The tissue is
interrogated by an ultrasonic transducer (140; T) that transmits to
an ultrasonic receiver (150; R) (or detector) at different
transmission angles and with different axes of transmission as in
FIG. 1C and FIG. 1D. The axis of transmission is shown as .alpha.
(or .beta.) and has a transmission path from T to R. The
transmission path passes through the tissue comprising skin (100),
soft tissue (represented as white), locations of organized
biomaterial (110) with acoustic properties different from that of
the extracellular fluid in the soft tissue (e.g. differences in
echogenicity, scatter, SOS, BUA, or reflection), amorphous,
insoluble biomaterial deposits (120) with acoustic properties
different from that of the extracellular fluid in the soft tissue
(e.g. differences in echogenicity, scatter, SOS, BUA, or
reflection), and dense tissue (130) with acoustic properties
different from that of the extracellular fluid in the soft tissue.
Comparison of the transmission paths of FIG. 1A and FIG. 1C shows
that the transmission path traverses tissue structures with
different acoustic properties due to the different physiological
states in the tissue at different times. Hence, the ultrasonic
measurements, such as the BUA or SOS, may not be the same depending
on the physiological state of the interrogated tissue. Assessment
of such differences in physiological states can be more accurately
determined by either varying the transmission angle or the axis of
transmission in an anatomical region. FIG. 1E shows received
signals in such tissue in different physiological states and at
different transmission angles.
[0084] By way of introduction, and not limitation of the various
embodiments of the invention, the invention includes at least four
general aspects:
[0085] 1) an ultrasonic method of measuring speed of sound and
broadband ultrasonic attenuation at predetermined, multiple
transmission angles;
[0086] 2) a method of correcting measured speed of sound and
broadband ultrasonic attenuation for errors introduced by soft
tissues interposed in the beam path between the ultrasonic
transducers and the object to be measured using predetermined,
multiple transmission angles;
[0087] 3) an ultrasonic method reducing the artifacts from
variations in tissue structure that alter ultrasonic properties or
the ultrasonic transmission path by measuring ultrasonic properties
at predetermined, multiple transmission angles; and
[0088] 4) devices and systems to achieve or facilitate the methods
1 through 3.
[0089] These aspects of the invention, as well as others described
herein, can be achieved using the methods and devices described
herein. To gain a full appreciation of the scope of the invention,
it will be further recognized that various aspects of the invention
can be combined to make desirable embodiments of the invention. For
example, the aspects 1 and 3 of the invention can be combined
thereby improving reproducibility of measurements of SOS and BUA
even further.
3.0 Automated System for Interrogating at Multiple Transmission
Angles Using Ultrasonic Transducers and Related Methods
[0090] Predetermined Axis of Transmission and Automated Multiple
Transmission Angle System
[0091] The present invention includes an ultrasonic system for
ultrasonic interrogation of tissue at multiple transmission angles
at single or multiple axes of transmission. The system is based, in
part, on improving ultrasonic measurements by creating a desired
axis of transmission or spatial relationship typically between two
ultrasonic transducers and their transmission paths (or reception
paths). In the preferred embodiments, the ultrasonic system is
adapted to interrogate dense tissues to measure either broadband
ultrasonic attenuation or speed of sound.
[0092] Typically, such a system includes a first ultrasonic
transducer with an axis of transmission in common with a second
ultrasonic transducer. The axis of transmission is usually through
a portion of a dense tissue and usually the transducers are not
permanently fixed but are capable of being repositioned to a
predetermined or desired location. In addition, in some embodiments
the positioner may also vary the transmission angle of the
transducer(s) in a predetermined fashion while maintaining an axis
of transmission in common between the two transducers. In other
embodiments, especially single transducer unit embodiments, the
transmission angle may vary and no axis of transmission is present
or maintained.
[0093] Typically, the two transducers can be aligned (e.g.
mechanically aligned) to have a common axis of transmission. In
such situations, the transducers will be generally directed at each
other to receive signals from each other. In some applications, the
transducers may not have an axis of transmission in common but are
instead arranged to each have a predetermined axis of transmission,
wherein each transducer may send signals that can be received by
the other transducer without having a common axis of transmission.
The axis of transmission for each transducer will have an angle of
transmission associated with it that can be varied. Preferably, the
transducers are adapted for BUA or SOS or both.
[0094] Alternatively, tandem transducers can be used wherein each
tandem transducer is comprised of 1) a transducer designed for A
scan or B scan, and 2) a transducer designed for either broadband
ultrasonic attenuation or speed of sound measurements or both. It
is understood that a tandem transducer can be paired so that, for
instance, the broadband ultrasonic transducer in the first tandem
transducer transmits signals and the broadband ultrasonic
transducer in the second tandem transducer receives signals.
[0095] In some embodiments the axis of transmission of each
transducer is predetermined or selected in advance of, or during,
transmission or reception of, ultrasonic waves. The axis of each
transducer can be adjusted or directed to permit either 1) a
partial overlap (typically less than about a twenty percent overlap
in the acoustic field), 2) a substantial overlap (typically more
than about a twenty percent overlap in the acoustic field), 3) a
complete overlap (typically more than about a ninety percent
overlap in the acoustic field) or 4) no overlap (typically less
than about a five percent overlap in the acoustic field) with an
axis of transmission of another transducer.
[0096] Partial overlap of each axis of transmission facilitates
interrogation of tissue from two separate interrogation sites while
permitting 1) interrogation of tissue by a single transducer (where
there is no substantial overlap of each axis of transmission) or 2)
interrogation of tissue by two or more transducers (where there is
a partial overlap of each axis of transmission). Typically, the
sites of interrogation are at least about 1 cm apart, often at
least about 4 cm apart and sometime 6 cm or more cm apart.
Transducers at interrogation sites can also be positioned on
different faces or sides of a tissue to be interrogated (e.g. on
the medial and lateral portion of an appendage). In many of these
embodiments the transducers receive signals from each other.
Preferably, tandem transducers are used that are adapted or
programmed to receive signals from each other. The invention,
however, is not limited to such embodiments and a plurality of
predetermined axes of transmission for plurality of transducers can
be established, wherein the transducers are either adapted to
receive signals from other transducers in the system or the signals
received and transmitted by each transducer are separately
processed. Similarly, substantial or complete overlaps can be
achieved if so desired in some embodiments.
[0097] Multiple transducers can also be used to create multiple
overlaps between each axis of transmission. Each axis of
transmission can overlap the same area in a tissue to permit
interrogation of the tissue by multiple transducers from separate
interrogation sites. For example, multiple transducers can be
directed to have overlapping axes of transmission to form a desired
interrogation volume or path in the tissue (e.g. an interrogation
volume substantially shaped like a column or cone). Multiple
transducers creating common interrogation volumes from separate
interrogation sites using overlapping axes of transmission can
improve resolution of internal structures or surfaces.
[0098] Without limiting aspects of the invention to a particular
mechanism of action, multiple transmission angles, multiple axes of
transmission and common interrogation volumes can give rise to
enhanced, or more precise, ultrasonic measurements due to any one
or combination of the following factors. In addition, these factors
may be applied to embodiments of the invention with a single
transducer unit or multiple transducers.
[0099] One, reduction in interference and scatter by comparing
ultrasonic properties (e.g. ultrasonic data in the form of A scan
or B scan) from each transducer and selecting the data with the
least amount of interference to use in a reconstruction, map or
ultrasonic analysis of the tissue.
[0100] Two, reduction in ultrasonic wave attenuation (not
necessarily broadband ultrasonic attenuation) by comparing
ultrasonic properties (e.g. ultrasonic data in the form of A scan
or B scan) from each transducer and selecting the data with the
least amount of attenuation to use in a reconstruction, map or
ultrasonic analysis of the tissue.
[0101] Three, signal averaging between each transducer
participating in multiple transmission angles, multiple axes of
transmission and common interrogation volumes. Such signal
averaging would typically account for the different interrogation
sites of each transducer, the amount of axis of transmission
overlap or selection of the most accurate data generated for each
transducer or a combination thereof.
[0102] Four, unreceived, anticipated signal analysis, which entails
analysing the absence of, or change in, signals that are
anticipated or predicted to be received by a detector. The absence
or change in signals will be indicative of the presence of
structures in the path that remove or alter the transmitted
ultrasonic signal.
[0103] In addition, interference, scattering and attenuation, as
well as other sources of error, may vary between transducers
because the transducers are located at separate interrogation sites
offering different interrogation paths with varying levels of
interference, scattering, attenuation, etc. This is based, in part,
on the property of ultrasonic hysteresis meaning either 1) the path
of an ultrasonic signal transmitted by a transducer through an
object of varying compositions with a heterogenous organization
returns to the transducer by a different path and with an altered
wave form or 2) the path of an ultrasonic signal transmitted by a
first transducer through an object of varying compositions with a
heterogenous organization will be received by a second transducer
by a different path and with an altered wave form compared to an
ultrasonic signal transmitted by the second transducer through the
same object and received by the first transducer.
[0104] For example, a model interrogation site has layers, from the
first side of the object to the second side of the object, of A, B,
and C. Wherein layer A, B and C all have different speed of sound
constants, and different microstructures contributing to
interference, attenuation and scatter. A signal moving from A to C
and back again will have traveled a different path than a signal
moving from C to A and back again. A transducer that transmits and
receives signals at an interrogation site on the surface of layer A
will receive a different set of signals compared to a transducer
that transmits and receives signals at an interrogation site on the
surface of layer C. Alternatively, a signal moving from A to C will
have traveled a different path than a signal moving from C to A. A
transducer that receives signals at an interrogation site on the
surface of layer C from a transducer sending signals from layer A
will receive a different set of signals compared to a transducer
that receives signals at an interrogation site on the surface of
layer A from a transducer located on the surface of layer C.
Consequently, the received signals will have different properties
dependent on the path taken through the object. In addition, these
observations may be applied to embodiments of the invention with a
single transducer unit or multiple transducers.
[0105] The different interrogation paths of each transducer offers
the ability to sample the data from each path and select the best
or appropriate data using defined selection criteria, thereby
reducing the source of error or enhancing interrogation of the
tissue. For example, in an interrogation of a tibial region a
transducer placed on the anterior surface of the tissue may have a
sharp and intense reflective surface 1 cm below the surface of the
skin indicating bone. The same interrogation site will have little
ability to interrogate the muscle "behind" the bone. A second
transducer positioned at a second interrogation site on the
posterior region of the same tibial region will offer relatively
greater ability to interrogate the muscle "behind" the bone
compared to the first interrogation site since the muscle is now
interrogated using ultrasonic waves that have not been deflected
off or attenuated by bone. Data analysis that selects and combines
data from each interrogation, and optionally including signal
averaging, can be used to generate a reconstruction, map, or
ultrasonic analysis of the tissue. Such positioning methods and
devices can be used with BUA or SOS, as well as imaging
techniques.
[0106] Methods and devices used to generate multiple transmission
angles, multiple axes of transmission and common interrogation
volumes, as well as other methods and devices herein, can aid in
producing ultrasonic assessments of the tissue, anatomic maps of
the tissue or imaging of the tissue. It can also be used in
conjunction with invasive procedures as a guide or monitor of the
progress of the procedure, such as catheterization, trocar based
procedures or other types of surgery.
[0107] Some examples of different embodiments of tandem transducers
related to an axis of transmission are as follows:
[0108] 1) a common axis of transmission with each transducer
substantially orthogonal to the tissue plane,
[0109] 2) a common axis of transmission with each transducer not
substantially orthogonal to the tissue plane (e.g. a first
transducer has a transmission angle 75 degrees and a second
transducer has a transmission angle of 105 degrees),
[0110] 3) a predetermined axis of transmission for a first
transducer and a second transducer, wherein there is a partial
overlap of each predetermined axis of transmission of the first and
second transducer and each transducer is substantially orthogonal
to the tissue plane, and
[0111] 4) a predetermined axis of transmission for a first
transducer and a second transducer, wherein there is a partial
overlap of each predetermined axis of transmission of the first and
second transducer and each transducer is not substantially
orthogonal to the tissue plane.
[0112] In addition, some examples of different embodiments of a
plurality of transducers (e.g., 2, 3, 4, 5, 6 or more) related to a
desired interrogation volume are as follows:
[0113] 1) a desired interrogation volume generated from a common
axis of transmission with each transducer substantially orthogonal
to the tissue plane,
[0114] 2) a desired interrogation volume generated from a plurality
of transducers each having an axis of transmission at a
predetermined angle with respect to the other transducers or the
tissue plane (e.g. a first transducer has a predetermined angle of
60 degrees with respect to a second transducer and a predetermined
angle of 120 degrees with respect to a third transducer), and
[0115] 3) a desired interrogation volume generated from a
predetermined axis of transmission for a first transducer and a
second transducer, wherein there is a partial overlap of each
predetermined axis of transmission of the first and second
transducer and each transducer is substantially orthogonal to the
tissue plane.
[0116] Generally, the system will include an x, y positioner that
engages the first ultrasonic transducer and the second ultrasonic
transducer to locate each transducer in the appropriate position on
the object to be interrogated. The x,y positioner can be designed
to vary the transmission angle of the transducer(s). Usually, the
x, y positioner positions the first ultrasonic transducer and the
second ultrasonic transducer while generally maintaining the axis
of transmission. The x,y positioner can be designed to include
positioning of each transducer independently or positioning of each
transducer while simultaneously maintaining a common axis of
transmission. The x, y positioner can position the ultrasonic
transducer at a desired location along the x axis and y axis of the
system. Typically, the x axis is the horizontal axis and the y axis
is vertical axis.
[0117] A computational unit can be included in the system to manage
ultrasonic measurements. Typically, the computational unit is
designed to manage ultrasonic signal transmission and reception of
the first ultrasonic transducer and the second ultrasonic
transducer. It may also be designed to optionally control movement
of the x, y positioner. By monitoring signal transmission and
reception the computational unit can instruct the x, y positioner
to appropriately locate the transducers in order to achieve the
desired relationship between the axis of transmission of each
transducer. For example, one method of instructing a positioner and
interrogating a tissue is based on predetermined multiple angles of
interrogation with respect to common anatomical region in the
tissue. In such case, all transmission paths substantially pass
through such point.
[0118] In many instances the computational unit can be programmed
to instruct the x, y positioner to establish a common axis of
transmission between the two transducers. As described herein, this
is a particularly useful embodiment for broadband ultrasonic
attenuation and speed of sound measurements in the human heel. It
is also contemplated to use such a system in other anatomical
regions where ultrasonic measurements would benefit from controlled
or predetermined x, y positioning with two or more probes (e.g.
imaging) along with multiple interrogation paths. Typically, the
computational unit is programmed to generate multiple transmission
paths or angles using either A scan or B scan data or both.
Multiple transmission paths can also be generated using other
ultrasound parameters, e.g. flow information acquired with
ultrasonic contrast agents.
[0119] Another embodiment of the invention relates to methods of
interrogating a tissue, generating multiple interrogation paths at
an anatomical region and instructing a positioner to change the
angle of transmission of the transducer(s). Multiple transmission
paths are generated from data obtained by interrogating the tissue
at a first transducer(s) transmission angle(s) (n.sub.1). This can
be done using any ultrasonic measurement, such as A scan or B scan
or both. A clinical measurement is then made at the first
transmission angle n.sub.1. Any clinical measurement can be used
including, SOS, BUA, echogenicity, reflective surfaces, and
ultrasonic images. Multiple transmission paths can also be used to
guide a surgical procedure. The process of interrogating with
multiple transmission angles can be repeated at subsequent
transmission angles (n.sub.1, n.sub.2, . . . ). Optionally, the
ultrasonic measurements can be can be compared at different angles
or averaged and stored in the computational unit. The process of
obtaining measurements at multiple angles can be repeated until the
desired data is obtained. Typically, the positioner moves the
transducer in increments until the desired predetermined
transmission angle has been reached and the tissue is interrogated
for clinical measurement, such as speed of sound or broadband
ultrasonic attenuation measurement. Such methods can be adapted as
instructions for components of a monitoring system that form a
computer program product.
[0120] A system that includes one, two, or more ultrasonic
transducers, an x,y positioner for generating multiple transmission
angles and a computational unit for signal management and
transducer positioning offers a number of advantages. First,
transducer positioning for multiple transmission angles can be
automatically established without significant operator
intervention, as well as with operator direction to a desired
position. Second, accuracy and reproducibility of transducer
positioning and generation of transmission angles can be improved
by appropriately programming the computational unit. Finally,
adjustments to transducer transmission angles during interrogation
can be accomplished with minimized interruption of the
interrogation process.
[0121] The system may optionally include a z positioner that
engages and/or positions at least one or more ultrasonic
transducers. Preferably, both transducers can be positioned in the
z dimension by the z positioner. The z positioner changes the
distance of transmission along the axis of transmission between the
first ultrasonic transducer and the second ultrasonic transducer.
Typically, it changes the distance between the transducer and the
interrogation with minimal compression of the interrogated tissue.
A pressure sensor can be included on the surface of the transducer
or other location to monitor transducer pressure against the
interrogated tissue. The pressure sensor can be part of control
unit to regulate the amount of transducer pressure at the
interrogation site by adjusting the transducer location in the z
dimension with the z positioner. If desired, an electronic feedback
loop can be included to adjust the transducer position in the z
dimension in response to changes in pressure, which could arise
from patient movement, tissue swelling or other factors that
contribute to changes in transducer pressure. The z positioner can
position the ultrasonic transducer at a desired location along the
z axis of the system. Typically, the z axis is the axis
perpendicular to the x axis which is the horizontal axis, and the y
axis is the vertical axis. The z positioner moves the transducer(s)
along the z-axis further or closer to the surface of the anatomical
location.
[0122] The system may optionally include, or be designed as a
dedicated device, to achieve speed of sound or broadband ultrasonic
attenuation measurements or both. Typically, in such a system the
computational unit can estimate speed of sound or broadband
ultrasonic attenuation in an interrogated tissue. Preferably, the
computational unit can correct the speed of sound or broadband
ultrasonic attenuation measurements for errors generated by soft
tissue effects. The database may also be comprised of factors
related to empirical measurements of soft tissue and broadband
ultrasonic attenuation, including historic patient records for
comparison.
[0123] The x, y positioner included in the system can be any
positioner that can accurately position a transducer and maintain
the transducer position during interrogation. The x, y positioner
can be those known in the art of positioning devices or those
developed in the future or disclosed herein. In selecting an x, y
positioner the following features should considered and
incorporated into the x, y positioner design depending on the
application: 1) ease of movement of the positioner preferably with
automated control, 2) integration of the positioner into a computer
control system, 3) accuracy of positioning (preferably within about
.+-.5 mm, more preferably about .+-.1 mm and most preferably about
.+-.0.05 mm), 4) speed of achieving a new position should typically
be less than 2 to 4 seconds, and 5) ability of the x, y positioner
to either locate one transducer or two transducers. It is
understood that the x, y positioner may be configured in many
arrangements. For instance, the x, y positioner may designed as one
positioning system that moves each transducer concurrently or as
two x, y positioners that move each transducer independently yet in
a coordinated fashion with respect to each transducer. The x, y
positioner can be manually controlled, operator computer
controlled, or automatically controlled with minimal or no operator
intervention or a combination thereof. Preferably, the system is
capable of all three modes of operation. If a manual mode is
incorporated into the device, the x, y positioner typically
includes a grip to manually direct the first and second transducers
over a desired anatomic region. Positioners in the art may used as
well, such as those provided by Newport (Irvine, Calif.), including
stages for rectilinear motion.
[0124] In one embodiment the x, y positioner can comprise a frame
to maintain the axis of transmission between the first and second
ultrasonic transducers. In this embodiment the x, y positioner
maintains a "fixed" axis of transmission. Typically, these types of
positioners can be less expensive to operate and robust under a
variety of clinical conditions because the axis of transmission is
fixed, typically during manufacture or in an adjustment protocol.
Thus, the x, y positioner is not required to locate the transducer
with respect to one another since this is predetermined. Instead
the x, y positioner can be primarily designed to locate the
transducer in tandem with a fixed common axis of transmission in
relation to the anatomic region of interrogation. Typically, the
frame engages an x track and the x track engages a y track, thereby
an operator can move the first and second ultrasonic transducers
manually in either an x or y dimension or combination thereof with
respect to an anatomic region. It is understood, however, that such
tracks could also be located on separate frames without a fixed
common axis of transmission between the two transducers and that a
common axis of transmission could be established. The x,y
positioner can be designed to accommodate an appendage. Typically,
the appendage is held in a predetermined position in the ultrasonic
system relative to the x,y positioner. Preferably, the x,y
positioner is automatically controlled by the computational unit.
In one arrangement, the computational unit instructs an x
servo-motor to drive the first ultrasonic transducer and second
transducer in the x dimension and a y servo-motor to drive the
first ultrasonic transducer and second transducer in the y
dimension.
[0125] FIG. 2A shows an example of a typical prior art device for
measuring the speed of sound or broadband ultrasonic attenuation in
a healthy non-edematous patient. The position of the patient's foot
200, of the calcaneus 210, and of the ultrasonic interrogation site
220 are fixed with respect to the device frame 230.
[0126] FIG. 2B shows an example of a typical prior art device for
measuring the speed of sound or broadband ultrasonic attenuation in
a patient with peripheral edema. Edema increases the thickness of
the soft tissue inferior and posterior to the calcaneus. Since the
position of the ultrasonic interrogation site 220 is fixed relative
to the device frame 230, a more inferior and posterior region is
measured within the calcaneus 210 when compared to FIG. 2A that is
even partially outside the calcaneus 210.
[0127] By interrogating at multiple transmission angles as
described herein, changes in probe position, such as those
described in FIG. 2A and FIG. 2B, can be compensated for or reduced
(see FIG. 3C through FIG. 3G).
[0128] FIG. 3A shows an embodiment of the invention comprising two
ultrasonic transducers 300 attached to an x-positioner 310 and a
y-positioner 320. The heel 330 and the calcaneus 340 are seated on
a foot holder 350. The ultrasonic transducer 300 is brought in
contact with the heel 330 using a z-positioner member 360 that can
move in and out of a frame 370 continuously or in a stepwise
fashion. The ultrasonic transmission axis 380 is also shown.
[0129] FIG. 3B is a side view of the ultrasonic transducer (T) 300,
the x-positioner 310, and the y-positioner 320 shown in FIG. 3A
showing the tracks of each postioner. Typically, one positioner
will engage the other positioner to permit x, y movement either
concurrently (moving in both directions simultaneously) or
sequentially (moving in one dimension first and then in a second
dimension).
[0130] FIG. 3C shows another embodiment of the invention. The
ultrasonic transducers 300 are attached to a positioning system 390
that affords movement of the transducers in x, y-, and z-direction,
as well as angulation of the transducers 300 and the resultant
ultrasonic transmission axis 380. The angulation position of the
transducers 300 and the ultrasonic transmission axis 380 is
substantially zero.
[0131] FIG. 3D shows the ultrasonic transducers 300 attached to a
positioning system 390 that affords movement of the transducers in
x, y-, and z-direction, as well as angulation of the transducers
300 and the resultant ultrasonic transmission axis 380. The
angulation position of the transducers 300 and the ultrasonic
transmission axis 380 is substantially different from zero.
[0132] FIG. 3E shows an expanded view of the embodiment presented
in FIGS. 3A-D. The ultrasonic transducer 300 is attached to a
positioning system 390 that affords movement of the transducers in
x, y-, and z-direction, as well as angulation of the transducers
300. The ultrasonic beam 395 has substantially zero angulation.
[0133] FIG. 3F shows an expanded view of the positioning system 390
and the ultrasonic transducers 300 with inferior angulation of the
ultrasonic beam 395.
[0134] FIG. 3G shows a magnification view of the positioning system
390 and the ultrasonic transducers 300 with superior angulation of
the ultrasonic beam 395.
4.0 Methods for Generating Multiple Transmission Angles
[0135] The invention also includes an ultrasonic method for
determining broadband ultrasonic attenuation or speed of sound
measurements in dense tissues, comprising:
[0136] interrogating a patient's tissue with at least a first
ultrasonic transducer unit at a first transmission angle and a
second ultrasonic transducer unit at a second transmission angle,
wherein said first ultrasonic transducer unit and said second
ultrasonic transducer unit are a) adapted for either 1) broadband
ultrasonic attenuation or 2) speed of sound measurements or both
and b) have an angle of least about 150 degrees between said first
ultrasonic transducer unit and said second transducer unit,
[0137] interrogating said patient's tissue with said first
ultrasonic transducer unit at a third transmission angle and said
second ultrasonic transducer unit a fourth transmission angle while
maintaining an angle of at least about 150 degrees between said
first transducer unit and said second transducer unit, and
[0138] determining dense tissue broadband ultrasonic attenuation,
dense tissue speed of sound or both for said tissue; wherein said
determining step generates a dense tissue broadband ultrasonic
attenuation value, dense tissue speed of sound value or both that
is more indicative of broadband ultrasonic attenuation or speed of
sound in dense tissue than in the absence of interrogating said
patient's tissue with at least said first ultrasonic transducer
unit at a third transmission angle and said second ultrasonic
transducer unit a fourth transmission angle.
[0139] The invention also includes an ultrasonic system for
determining broadband ultrasonic attenuation or speed of sound
measurements in a tissue, comprising:
[0140] a transducer unit comprising at least a first ultrasonic
transducer engaged with a first multiple transmission angle unit to
controllably vary first transmission angles and a second ultrasonic
transducer engaged with a second multiple transmission angle unit
to controllably vary second transmission angles, wherein the first
ultrasonic transducer unit and the second ultrasonic transducer
unit are adapted for either 1) broadband ultrasonic attenuation or
2) speed of sound measurements or both, and
[0141] a computational unit for controllably adjusting transmission
angles of the first and second transducer; wherein the ultrasonic
system will measure broadband ultrasonic attenuation value, speed
of sound value or both if so desired.
[0142] Typically, transmission angles can differ in 1, 2, 3, 4, 5,
6, 7, 8, 9 or 10 degree increments or multiples thereof.
Preferably, a series of transmission angles will be used, as
measured with respect to the object plane, such as 90, 85, 80, 75,
70, 65 and 60 degrees. It will be readily apparent to those skilled
in the art that transmission angles of 90, 95, 100, 105, 110, 115
and 120 degrees can also be used. In some embodiments, selection of
the transmission angle is based on whether a common axis of
transmission is desired.
[0143] In various embodiment of the invention, transmission angles
can converge or diverge from an ultrasonic source or sources.
Generally, there is seldom a limitation as to whether convergent or
divergent transmission angles can be used in the invention. Some
applications will, however, operate more effectively by selecting
the appropriate angle arrangement. To retain a narrower field of
interrogation, a single ultrasonic source can be used at relatively
small divergent angles, such as no more than about a 20 to 30
degree total divergence in transmission angles. For a wider field
of interrogation, multiple ultrasonic sources can be used with
divergent angles. If a narrow field of interrogation is desired,
multiple ultrasonic sources can be used with convergent
transmission angles.
[0144] To vary transmission angles, typically a first pulse has a
first transmission angle with respect to the object plane and a
second pulse has a second transmission angle with respect to the
object plane, wherein there is a predetermined divergent angle
between the first and second pulse or a convergent angle between
the first and second pulse. The predetermined divergent or
convergent angles can be selected to improve the measurement of a
ultrasonic parameters generated in A scan or B scan. The selection
of transmission angles typically takes into account the depth in
the field where the target reflective layer (or layers) is likely
to be located (target reflective layer depth), the likely thickness
of the target reflective layer (target reflective layer thickness),
object composition and distances between ultrasonic sources (if
multiple sources are used). Generally, the total range of
transmission angles a will not be greater than 45 degrees, and
preferably 30 degrees or less.
[0145] The divergent angle separates a first position and second
position of an ultrasonic source or sources and the first pulse has
a centered first axis of transmission and the second pulse has a
centered second axis of transmission, wherein the first and second
axis do not converge. Usually the divergent angle between the first
and second pulse is between 5 to 90 degrees, and preferably between
about 5 and 20 degrees.
[0146] The convergent angle separates a first position and second
position of an ultrasonic source or sources and the first pulse has
a centered first axis of transmission and the second pulse has a
centered second axis of transmission, wherein the first and second
axis converge. Usually the convergent angle between the first and
second pulse is between 5 to 90 degrees, and preferably between
about 5 and 20 degrees.
[0147] Different transmission angles can be accomplished by any
method known, developed in the art or in the future or described
herein. Typically, the invention includes three different methods
(with the corresponding devices) for varying the transmission
angle: 1) mechanically changing position of the transducer(s) with
respect to the plane of the tissue, 2) providing multiple
transducers with predetermined positions that correspond to
predetermined transmission angles and 3) steering ultrasonic beams
from multiple ultrasonic sources (typically arrays) with
predetermined firing sequences. For cost effective production of
devices only one of these methods will typically be used in a
device. If more sophisticated devices are desired, such methods can
also be combined to gain the benefit of the different methods.
[0148] To vary transmission angles using a mechanical device,
typically the first and second pulses are from a first ultrasonic
generator. The first generator has at least a first and a second
position. The first and second position typically are mechanically
connected. The generator is guided from the first position to the
second position with a mechanical connection. The first and second
position (or more positions for more transmission angles) for the
ultrasonic generator can be connected using any connection that
changes the transmission angle of the ultrasonic generator in an
accurate and controllable fashion. Typically, a sweep through all
of the desired positions, either in increments or continuously,
should be completed within about 0.02 to 2 seconds, preferably
within 200 to 500 milliseconds and more preferably within 20 to 200
milliseconds. These time values also apply to other methods of
varying the transmission angle. Such a device can be mounted on or
engaged by an x, y positioner to locate the tranducers at a desired
anatomical region.
[0149] In one embodiment, the invention utilizes a mechanical
connection comprising a mechanical motor that can oscillate a
generator(s) at least once from the first to the second position
(or more positions) in order to vary the transmission angle. This
device can be used to create maps, identify anatomical landmarks,
and measure BUA or SOS or other ultrasonic methods described
herein. The mechanical motor typically provides a frame time of
oscillation from 10 to 2500 ms. Any mechanical motor that can
produce a position change in such a time frame in response to an
electrical command signal and can be adapted for use in a hand-held
probe can be preferably used to vary the transmission angle of
ultrasonic generators, such as crystals or arrays of crystals. Such
a device can be mounted on or engaged by an x, y positioner to
locate the tranducers at a desired anatomical region.
[0150] In one design the mechanical motor has at least a first and
second magnet to move the ultrasonic generator on a track, and the
generator further comprises a magnetic source or magnetically
attractive material that magnetically communicates with the first
or second magnet to change the transmission angle. Magnetic
switching of an ultrasonic generator position is particularly
desirable because the magnet can be turned off and on relatively
rapidly, and directed to change polarity relatively rapidly. Such
magnetic systems can provide smooth position changes and relatively
noise free performance. The track can be any mechanical device that
directs the ultrasonic generator between positions. In some
instances the track will comprise a groove that engages the
ultrasonic generator and permits the ultrasonic generator to pivot
around an axis to allow for the probe to sweep across the desired
transmission angles. First and second magnet refers to magnets that
can be used to move an ultrasonic source from a first to a second
position. Magnets may be permanent or induced by applying an
electric current to the appropriate electronic device. For example,
an electric current can be applied to a wire arranged in a loop or
coil-like configuration and the magnetic field created can be
controlled by a predetermined electrical switch. The current
induces a magnetic field that can be manipulated depending on the
pattern of applied current or by the design of the coil or both.
Additional magnets can be used for additional position for multiple
placement.
[0151] In another embodiment, the invention utilizes permanently
fixed ultrasonic generators with different, individual transmission
angles to accomplish mapping, anatomical landmarks, BUA or SOS, or
other ultrasonic methods described herein. Typically, a first pulse
is from a first ultrasonic generator and second pulse is from a
second ultrasonic generator, wherein the first and second
ultrasonic generators are permanently fixed in a first and a second
position. More than two ultrasonic generators can be used as well
but usually not more than about 10 ultrasonic generators will be
used in this embodiment, unless they are arrays of crystals.
[0152] In another embodiment, the invention utilizes predetermined
patterns of ultrasonic source activation that result in different
transmission angles to accomplish mapping, anatomical landmarks,
BUA or SOS, or other ultrasonic methods described herein. For
example, a predetermined pattern of ultrasonic source activation
can comprise 1) a first series of trigger pulses that sequentially
fires an array of ultrasonic crystals starting from a first end to
a second end of the array and 2) a series of trigger pulses that
sequentially fires the array from a second end to a first end of
the array. The first series of pulses have a biased direction along
a first portion of the field of the interrogated object, i.e. the
beams are steered to one side of the field. This sequence of pulses
can be repeated at different time frames in order to change the
average transmission beam angle. Similarly, the second series of
pulses have a biased direction along a second portion of the field
of the interrogated object, i.e. the beams are steered to a second
side of the field. This sequence of pulses can be repeated at
different time frames in order to change the average beam angle.
With linear arrays this method permits the use of either divergent
or convergent transmission angles without mechanically moving the
ultrasonic source to change the transmission angle. Averaged beams
obtained by this method with different transmission angles can then
be used to calculate BUA or SOS or other ultrasonic methods as
described herein.
[0153] As part of the predetermined pattern of ultrasonic source
activation, simultaneous triggering pulses may also be used in
conjunction with sequential firing patterns. Simultaneous firing of
the ultrasonic sources effectively provides a series of beams,
which can be optionally averaged, to provide orthogonal probe
position relative to a reference plane. When the ultrasonic source
is orthogonal to the object/tissue plane, the transmission angle of
simultaneously fired beams will be ninety degrees. If the probe has
a non-orthogonal position, then the transmission will be more or
less than ninety degrees. By comparing the signals generated from
sequentially fired pulses to simultaneously fired pulses, the
deviation from an orthogonal probe position can be calculated to
accomplish mapping, anatomical landmarks, BUA or SOS or other
ultrasonic methods described herein. Comparison of ultrasonic
parameter (e.g. BUA or SOS) from the averaged signals of both the
sequentially generated pulses and the simultaneously generated
pulses will be indicative of the difference in tissue structure
ascertained at different transmission angles. If so desired, this
information can be transmitted back to the operator, for instance
on a monitor, to alert the operator to tissue abnormalities or
status. Once the operator has evaluated the results, the operator
may instruct the system to adjust the probe to achieve orthogonal
probe alignment for interrogation of that particular tissue.
[0154] The trigger pulses described herein can be particularly
optimized to enhance measurement of BUA or SOS in vivo, such as in
humans or other objects described herein. To steer a series of
beams to create an averaged beam with a specific transmission
angle, each ultrasonic crystal is triggered with a 1 .mu.s to 500
.mu.s delay between the firing of each crystal. By increasing the
delay between firing each crystal, the depth of interrogation and
the transmission angle of the averaged beam can be changed.
Ultimately, depth of interrogation will be limited by the
dimensions of the transducer near and far field (Bushberg, J. T.,
Seibert, J. A., Leidholdt, E. M., Boone, J. M., The Essential
Physics of Medical Imaging 1-742 (1994)). The trigger pulses are
timed to delay, such as an exponential delay, the firing of the
crystals (e.g., crystals 1-5) over a 15 .mu.sec time period. The
firing sequence causes a delay across the array in order to steer
to the target and provide an averaged beam (of five beams in this
example) with a predetermined transmission angle, e.g. 75
degrees.
[0155] The invention also includes an ultrasonic method for
generating an anatomic landmark for ultrasonic interrogation of an
anatomical region, comprising:
[0156] a) positioning, if necessary, on the surface of a patient,
with respect to an anatomical region, an ultrasonic transducer unit
comprising either 1) a first ultrasonic transducer that can
transmit and receive signals or 2) a pair of ultrasonic transducers
wherein a first member of the pair is designed to transmit signals
and a second member of the pair is designed to receive signals,
and
[0157] b) interrogating the anatomical region with the ultrasonic
transducer unit at a first transmission angle,
[0158] c) interrogating the anatomical region with the ultrasonic
transducer unit at a second transmission angle,
[0159] d) identifying an anatomic landmark in common with the
signals obtained in the above steps in the anatomical region with
an ultrasonic property of the anatomical region.
[0160] This ultrasonic method can further comprise the steps of
comparing the location and axis of transmission of the ultrasonic
transducer unit to the location of the anatomic landmark and
positioning the ultrasonic transducer unit to produce an axis of
transmission generally through the anatomic landmark. Steps a, b,
and c can be optionally repeated. This can increase accuracy or
permit close matching of observed landmarks with reference maps or
landmarks. Each positioning step can be performed in relation to an
anatomic landmark. The positioning steps are typically performed to
generate an axis of transmission substantially through the anatomic
landmark. Although the transmission axis can be in a predetermined
coordinate or desired spatial relationship with respect to the
landmark. The positioning steps can be performed to in relation to
a reference anatomic landmark of the anatomical region that is
stored in retrievable form a storage device.
[0161] In some embodiments, it will be desirable to generate
anatomical maps and landmarks, as well as images, with signals from
multiple transmission and detection angles. Generally, it will be
desirable to place the probe in a position that is substantially
orthogonal to the object plane. In many situations, it will be
desirable to transmit a series of pulses at different transmission
angles, usually about 5 to 10 degrees apart. This permits
generating an image or alternatively a map or landmark from
different interrogation paths.
EXAMPLES
[0162] The following materials and methods are exemplary of the
materials and methods that can be used to achieve the results
described herein. These examples are for illustrative purposes
only, and are not to be construed as limiting the appended claims.
One skilled in the art will readily recognize substitute materials
and methods.
General Materials and Methods
[0163] In vivo ultrasonic measurements are performed using a
prototype ultrasonic system capable of measuring speed of sound and
broadband ultrasonic attenuation in the heel region. The device is
also capable of measuring distances between different
acoustic/tissue interfaces using A-scan technique.
[0164] The ultrasonic system consists of two ultrasonic sources
mounted on a U-shaped plastic frame. A hinge is located in the
center portion of the U-shaped plastic frame that allows for
adjusting the distance between the ultrasonic transducers for each
individual patient. The physical distance separating both
transducers is registered for each patient using an electronic
system that employs a potentiometer. The U-shaped plastic frame is
connected to a plastic housing on which the patient can rest the
fore-and mid-foot and in particular the heel comfortably. The
ultrasonic sources are placed by the operator on the left and the
right side of the foot in the heel region. An ultrasonic gel is
used for acoustic coupling. The operator adjusts the frame and the
attached ultrasonic sources visually so that they are flush with
the skin and near perpendicular to the skin surface.
[0165] The ultrasonic system is designed with a central processing
unit responsible for pulsing the ultrasonic transducer(s) and
crystal(s), registering signals returned from the transducer,
preamplification of the electronic signal, time gain compensation,
signal compression, signal rectification, demodulation, and
envelope detection, signal rejection, signal processing, analysis
and display of SOS, BUA, and soft tissue and bone distance
measurements. Transducers operate at a center frequency of 1 Mhz.
However, transducer center frequency can be switched from 1 to 0.5
MHz. As the interrogation frequency of the micro-transducer
decreases, generally, the ability to resolve reflective surfaces at
deeper depths improves. The lower frequency is used in obese or
edematous patients in whom tissue penetration with the 1 MHz probe
is insufficient.
[0166] With each measurement the device registers initially the
physical distance between both transducers. The device then
measures (a) speed of sound, and (b) broadband ultrasonic
attenuation. Broadband ultrasonic attenuation is calculated by
subtracting the amplitude spectrum of a patient from one obtained
in a reference material (e.g. de-gassed water).
[0167] As an alternative to ultrasonic distance measurements using
A-scan technique, ultrasonic measurements can also be performed
using another prototype system that is capable of two-dimensional
image acquisition and display using B-scan technology in addition
to SOS and BUA measurements. This ultrasonic system also uses two
or more ultrasonic sources mounted on a hinged, U-shaped plastic
frame. The physical distance separating both transducers is
registered for each patient using an electronic system. After
positioning of the patient and the transducers and application of
the acoustic coupling gel, images are acquired in B-scan mode
followed by SOS and BUA measurements. Images are displayed on a
computer monitor attached to the scanner hardware.
[0168] All experiments performed on animal subjects (including
humans) shall be performed with the highest ethical and medical
standards and in accordance with the relevant laws, guidelines and
regulations of the relevant governing jurisdiction(s) or
professional association(s), including, where appropriate,
compliance under 45 CFR 46 relating to United States federal policy
for the protection of human subjects.
Example 1
Correction for Edema-Induced Changes in Ultrasonic Probe Position
and Its Influence on In-Vivo Reproducibility of Calcaneal Speed of
Sound and Broadband Ultrasonic Attenuation
[0169] This example shows among other things that presence of
peripheral edema does not only affect soft tissue thickness in the
beam path thereby altering SOS and BUA directly but also affects
ultrasonic probe position relative to the underlying bone. This
examples documents that edema induced changes in ultrasonic probe
position over the calcaneus and general variations in ultrasonic
probe position over the calcaneus reduce short-term and long-term
in vivo precision of SOS and BUA measurements.
[0170] Twenty patients with compromised cardiac performance and
peripheral edema are selected for the study. SOS and BUA
measurements are performed at different times in the day on two
different days: In the morning on day 1 before 9 am and in the
evening on day 2 after 6 pm. At each time interval, the degree of
peripheral edema is assessed clinically by visual inspection and
manual palpation. Using standard clinical techniques (see Bates et
al., J. B. Lippincott, 1995), edema is subdivided into 5
grades:
[0171] 0.) absent,
[0172] 1.) slight,
[0173] 2.) mild,
[0174] 3.) moderate, and
[0175] 4.) severe.
[0176] Ultrasonic measurements are performed in each patient using
a first prototype ultrasonic system that is capable of SOS and BUA
measurements. The patient's foot is secured in the ultrasonic
device so that the heel of the foot rests on the heel pad of the
device and the posterior aspect of the heel touches the back-wall
of the instrument (see also FIGS. 2A and 2B). A small amount of
acoustic coupling gel is applied to the skin and the ultrasonic
transducers are placed against the skin at the measurement site.
The position of the foot is not corrected for any changes in
position induced by peripheral edema.
[0177] SOS and BUA measurements are then repeated using a second,
different prototype ultrasonic system. This second system is
capable of identifying the posterior contour and the inferior
contour of the calcaneus on the B-scan images. Using these
landmarks, the system positions the ultrasonic transducers
automatically over a predefined region in the calcaneus, e.g. 1.5
cm anterior to the posterior calcaneal cortex and 1.5 cm superior
to the inferior calcaneal cortex. In this fashion, the ultrasonic
transducers are reproducibly positioned over the same measurement
site in the calcaneus regardless of changes in the thickness of the
posterior and inferior heel soft tissue pad.
[0178] In-vivo reproducibility between am and pm measurements is
better with the second ultrasonic system that adjusts probe
position relative to the posterior and the inferior cortex of the
calcaneus than with the first prototype system with fixed probe
position relative to skin/patient/heel surface.
Example 2
Correction for Edema-Induced Changes in Ultrasonic Probe Position
and Its Influence on In-Vivo Reproducibility of Calcaneal Speed of
Sound and Broadband Ultrasonic Attenuation Before and After
Diuretic Therapy
[0179] The experimental design used in this example is identical to
that shown in Example 1. However, rather than assessing the
influence of diurnal changes in tissue edema between morning and
evening measurements, twenty patients with compromised cardiac
performance and peripheral edema are studied prior to and two weeks
after initiation of diuretic therapy.
[0180] The results show that in-vivo reproducibility of SOS and BUA
is better when the ultrasonic system is capable of adjusting probe
position relative to the anatomic landmarks, e.g. posterior and
inferior cortex, of the calcaneus than with an ultrasonic system
where the probe position is fixed relative to skin/patient/heel
surface.
Example 3
Improvement in In-Vivo Reproducibility of SOS and BUA Measurements
of the Calcaneus Using Variable Ultrasonic Transmission Angles
[0181] This example shows among other things that the in vivo
reproducibility of ultrasound measurements of SOS and BUA can be
improved by using variable transmission angles.
[0182] Twenty patients with osteoporosis are selected for the
study. Patients undergo SOS and BUA measurements of the heel on two
separate days, baseline and repeat examination 24 hours later.
[0183] Using a first prototype ultrasonic system, SOS and BUA are
measured. The first prototype system is not capable of B-scan
imaging and transmission of ultrasonic signals at multiple
transmission angles.
[0184] The patients are then scanned using a second prototype
ultrasonic system. The second ultrasonic system is capable of
ultrasonic image acquisition and display using B-scan mode in
addition to SOS and BUA measurements. Furthermore, the ultrasonic
system is also capable to transmit and receive signals at different
transmission angles (a) from the same position, and (b) from
different positions. Using multiple image acquisitions at multiple
transmission angles and positions, the ultrasonic system identifies
the position and angle at which it achieves a match of the
posterior and inferior calcaneal contour that resembles that of
previous measurements obtained in a healthy reference population
most closely. Once the preferred position and angle resulting in
the best match have been identified, the ultrasound system measures
then SOS and BUA using that particular position and angle and
measuring an area 1.5 cm anterior to the posterior cortex and 1.5
cm superior to the inferior cortex.
[0185] Scans are repeated one day later: Initially, patients are
scanned using the first ultrasonic prototype system that is not
capable of B-scan imaging and transmission of ultrasonic signals at
multiple transmission angles.
[0186] Patients are then re-scanned on the second ultrasonic
prototype system. The second ultrasonic system acquires multiple
B-scan images at multiple different positions over the calcaneus
using multiple different transmission angles at each position. The
ultrasonic system identifies the posterior contour and the inferior
contour of the calcaneus on the B-scan images. As the transmission
angle changes, the contour formed by the posterior and inferior
cortex of the calcaneus changes. The ultrasound system performs a
matching procedure between the calcaneal contour measured on the
initial scan one day earlier and the calcaneal contour measured on
the second scan. Once the position and the transmission angle have
been identified that yield the closest match to the previous
measurement in the same patient, SOS and BUA are re-measured.
[0187] The results demonstrate the in vivo reproducibility of SOS
and BUA measurements improve markedly when using the second
ultrasound system that allows contour matching of the calcaneus and
signal transmission and reception at multiple transmission
angles.
Example 4
Improvement in Image Quality and Anatomic Accuracy of
Three-Dimensional Displays of Ultrasonic Data Using Computer
Controlled Two-Dimensional Ultrasonic Image Acquisition at Multiple
Transmission Angles
[0188] A patient with a renal cell carcinoma involving the inferior
pole of the left kidney is subjected to ultrasound scanning.
Initially, the patient is scanned using a standard clinical
ultrasound system (Acuson Sequoia.TM., Acuson, Mountainview,
Calif.) with a 3.5 MHz transducer. A physician trained in
diagnostic ultrasound holds the transducer in his hand. The
physician positions the ultrasound transducer over the area of the
tumor. The physician directs the transducer so that the tumor is
imaged in superoinferior orientation in the sagittal plane. The
ultrasound system provides real time images of the tumor. The depth
of interrogation is adjusted to include all tumor boundaries The
physicians then rotates the transducer with a sweeping motion of
his hand and wrist from medial to lateral while maintaining the
same skin contact area and while continuing to scan. In this
fashion, multiple images covering the mediolateral extent of the
tumor are acquired. The images are stored digitally and transferred
to an independent computer image analysis, reconstruction, and
viewing station. The computer station is used to generate
three-dimensional reconstructions of the tumor using echogenicity
based thresholding techniques with subsequent surface or volume
reconstruction techniques. The three-dimensional reconstruction of
the tumor is then used to quantify the tumor volume using
previously established techniques (see also Heuck et al., J Comp.
Assist. Tomogr. Vol. 13, No. 2, pp. 287-293, 1989).
[0189] The patient is then re-scanned using a prototype ultrasound
system that provides for acquisition of ultrasound images at
multiple transmission angles using a computer controlled multiple
transmission angle positioner. Images are also acquired in real
time mode with an ultrasonic transmission frequency of 3.5 MHz. The
physician directs the ultrasound transducer unit over the area of
the tumor where it is held in place by a computer controlled
positioner. The transducer unit is oriented so that the tumor is
imaged in superoinferior orientation in the sagittal plane. The
depth of interrogation is adjusted to include all tumor boundaries.
Once the transducer has been adequately positioned over the tumor,
the computer unit instructs the transducer to acquire multiple
images at multiple transmission angles through the tumor. Since
each transmission angle is computer defined, the exact
anatomic/spatial orientation of each image relative to the
transducer is known and stored along with the two-dimensional image
data. The data are stored digitally and transferred to an
independent computer image analysis, reconstruction, and viewing
station. The computer station is used to generate three-dimensional
reconstructions of the tumor using echogenicity based thresholding
techniques with subsequent surface or volume reconstruction
techniques. The three-dimensional reconstruction of the tumor is
then used to quantify the tumor volume using previously established
techniques (see also Heuck et al., J Comp. Assist. Tomogr. Vol. 13,
No. 2, pp. 287-293, 1989).
[0190] Finally, the patient is re-scanned using a contrast-enhanced
spiral CT scan through the abdomen. The contrast-enhanced spiral CT
images highlight the tumor very clearly agains surrounding, less
enhancing tissues. CT images are also transferred to an independent
computer workstation equipped with software for three-dimensional
image reconstruction using thresholding techniques with subsequent
surface or volume reconstruction. The resultant three-dimensional
reconstructions are also used to quantify the volume of the tumor
based on the CT data.
[0191] The results show that three-dimensional displays of
ultrasound images obtained using a computer controlled multiple
transmission angle positioner demonstrate less image artifacts and
correlate better with the 3D CT reconstruction than
three-dimensional displays of ultrasound images obtained using the
hand-held sweeping technique. The results show also that the 3D
tumor volume quantified based on three-dimensional displays of
ultrasound images obtained using a computer controlled multiple
transmission angle positioner correlates better with the tumor
volume quantified based on the 3D CT reconstruction than the 3D
tumor volume obtained based on three-dimensional displays of
ultrasound images obtained using the hand-held sweeping
technique.
[0192] Publications
1 U.S. PATENT DOCUMENTS 3,648,685 Mar. 14, 1972 Hepp, J. A., et al.
3,713,329 Jan. 30, 1973 Munger, D. W. 3,782,177 Jan. 1, 1974 Hoop,
J. M. 3,847,141 Nov. 12, 1974 Hoop, J. M. 4,043,181 Aug. 23, 1977
Nigam, A. K. 4,048,986 Sep. 20, 1977 Ott, J. H. 4,056,970 Nov. 8,
1977 Sollish, B. D. 4,224,829 Sep. 30, 1980 Kawabuchi, M., et al.
4,235,243 Nov. 25, 1980 Saha, S. 4,242,911 Jan. 6, 1981 Martin, H.
E. 4,361,154 Nov. 30, 1982 Pratt, G. W. 4,421,119 Dec. 20, 1983
Pratt, G. W. 4,446,737 May 8, 1984 Hottier, F. 4,522,068 Jun. 11,
1985 Smith, G. E. 4,530,360 Jul. 23, 1985 Duarte, L. R. 4,658,827
Dec. 21, 1987 He, P., et al. 4,688,428 Aug. 25, 1987 Nicolas, J.-M.
4,702,258 Oct. 27, 1987 Nicolas, J.-M., et al. 4,774,959 Oct. 4,
1988 Palmer, S. B., et al. 4,830,015 May 16, 1989 Okazaki, K.
4,913,157 Apr. 3, 1990 Pratt, G. W., et al. 4,930,511 Jun. 5, 1990
Rossman, P. J., et al. 5,042,489 Aug. 27, 1991 Wiener, S. A., et
al. 5,054,490 Oct. 8, 1991 Rossman, P. J., et al. 5,099,849 Mar.
31, 1992 Rossman, P. J., et al. 5,119,820 Jun. 9, 1992 Rossman, P.
J., et al. 5,218,963 Jun. 15, 1993 Mazess, R. B. 5,271,403 Dec. 21,
1993 Paulos, J. J. 5,343,863 Sep. 6, 1994 Wiener, S. A., et al.
5,349,959 Sep. 27, 1994 Wiener, S. A., et al. 5,452,722 Sep. 26,
1995 Langton, C. M. 5,483,965 Jan. 16, 1996 Wiener, S. A., et al.
5,603,325 Feb. 18, 1997 Mazess, R. B., et al. 5,649,538 Jul. 22,
1997 Langton, C. M.
[0193] Foreign Patent Documents
[0194] WO 80/02796 Jun. 9, 1980 Pratt, G.
[0195] Other Publications
[0196] Agren, M., et al., Calc Tiss Int, vol. 48, pp. 240-244,
1991.
[0197] Bates, B., et al., in: "A guide to physical examination and
history taking, 6th edition", Bates, B., et al., eds., pp. 427-447,
1995.
[0198] Biot, M. A., J Acoust Soc Am, vol. 34, pp. 1254-1264,
1962.
[0199] Bradenburger, G., et al., J Bone Miner Res, vol. suppl. 1,
pp. S184, 1992.
[0200] Dretakis, E., et al., Br J Radiol, vol. 67, pp. 636-638,
1994.
[0201] Faulkner, K. G., etal., Am J Roentgenol, vol. 157, pp.
1229-37, 1991.
[0202] Gluer, C. C., et al., J Bone Min Res, vol. 7 (9), pp.
1071-1079, 1992.
[0203] Gluer, C. C., et al., Calc Tiss Int, vol. 55, pp. 46-52,
1994.
[0204] Goss, S. A., et al., J Acoust Soc Am, vol. 64 (2), pp.
423-457, 1978.
[0205] Greespan, M., et al., J Acoust Soc Am, vol. 31, pp. 75-76,
1959.
[0206] Hans, D., et al., Bone, vol. 16, pp. 476-480, 1995.
[0207] Heuck, A. et al., J Comp. Assist. Tomogr. Vol. 13, No. 2,
pp. 287-293, 1989
[0208] Lang, P., et al., Radiol Clin North Am, vol. 29, pp. 49-76,
1991.
[0209] Langton, C. M., et al., Bone, vol. 18, 6, pp. 495-503,
1996.
[0210] Langton, C. M., etal., Eng Med, vol. 13, pp. 89-91,
1984.
[0211] McCloskey, E. V., et al., Clin Sci, vol. 78, pp. 221-227,
1990.
[0212] Njeh, C. F., et al., Med Eng Phys, vol. 18, pp. 373-381,
1996.
[0213] Rossman, P. J., et al., Clin Phys Physiol Meas, vol. 10, pp.
353-360, 1989.
[0214] Schott, A. M., et al., Osteoporosis Int, vol. 3, pp.
249-254, 1993.
[0215] Turner, C. H., et al., Calc Tiss Int, vol. 49, pp. 116-119,
1991.
[0216] Williams, J. L., J Acoust Soc Am, vol. 91, pp. 1106-1112,
1992.
[0217] Williams, P., et al. "Gray's anatomy, 36th British Edition",
1980.
[0218] Zagzebski, J. A., et al., Calc Tiss Int, vol. 49, pp.
107-111, 1991.
[0219] All documents and publications, including patents and patent
application documents, are herein incorporated by reference to the
same extent as if each publication were individually incorporated
by reference.
* * * * *