U.S. patent application number 11/597196 was filed with the patent office on 2008-08-14 for breast ultrasound scanning promoting patient comfort and improved imaging near chest wall.
Invention is credited to Jiayu Chen, Shih-Ping Wang, Zengpin Yu, Wei Zhang.
Application Number | 20080194959 11/597196 |
Document ID | / |
Family ID | 35502779 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080194959 |
Kind Code |
A1 |
Wang; Shih-Ping ; et
al. |
August 14, 2008 |
Breast Ultrasound Scanning Promoting Patient Comfort and Improved
Imaging Near Chest Wall
Abstract
An apparatus and related methods for scanning a breast are
described, the apparatus comprising a frame defining an orifice
shaped to allow the breast to be received therein, a compressive
member secured to the frame across the orifice that compresses the
received breast toward the patient's chest wall, and a transducer
positioned in acoustic communication with the compressive member
for imaging the breast therethrough. The frame holds a reservoir of
acoustically conductive fluid that maintains the transducer in
acoustic communication with the compressive member. In different
preferred embodiments having different advantages, the compressive
member comprises a flexible elastic membrane, a flexible inelastic
membrane, or a rigid sonolucent plastic preformed into the shape of
a chestwardly-compressed breast. Where the transducer comprises one
or more linear array probes, various probe orientations and
trajectories are described for generating a three-dimensional
volumetric representation of the breast having reduced nipple
shadow effects.
Inventors: |
Wang; Shih-Ping; (Los Altos,
CA) ; Zhang; Wei; (Union City, CA) ; Chen;
Jiayu; (Palo Alto, CA) ; Yu; Zengpin; (Palo
Alto, CA) |
Correspondence
Address: |
COOPER & DUNHAM, LLP
1185 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
35502779 |
Appl. No.: |
11/597196 |
Filed: |
May 23, 2005 |
PCT Filed: |
May 23, 2005 |
PCT NO: |
PCT/US05/18316 |
371 Date: |
August 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60577388 |
Jun 4, 2004 |
|
|
|
Current U.S.
Class: |
600/445 |
Current CPC
Class: |
A61B 8/54 20130101; A61B
8/483 20130101; A61B 8/4218 20130101; A61B 8/4281 20130101; A61B
8/0825 20130101; A61B 8/406 20130101 |
Class at
Publication: |
600/445 |
International
Class: |
A61B 8/13 20060101
A61B008/13 |
Claims
1. An apparatus for scanning a breast of a patient, comprising: a
frame defining an orifice, said orifice being shaped to allow at
least a portion of the breast to extend therethrough; a compressive
member secured to said frame across said orifice, a first side of
said compressive member compressing the breast toward a chest wall
of the patient when said breast is extended through said orifice;
and a transducer positioned in acoustic communication with a second
side of said compressive member opposite said first side for
imaging the breast therethrough.
2. The apparatus of claim 1, said orifice and compressive member
being positioned in an approximately horizontal plane to receive
the breast while the patient is in a substantially prone
position.
3. The apparatus of claim 2, wherein said compressive member
comprises a stretchable membrane elastically compressing the breast
upward toward the chest wall.
4. The apparatus of claim 3, wherein said stretchable membrane
exerts a total upward force on the breast in the range of
approximately 2 pounds (8.9 Newtons) to 12 pounds (53.4
Newtons).
5. The apparatus of claim 3, wherein said stretchable membrane
comprises an elastomer selected from the group consisting of:
silicone, latex, vinyl, nitrile, polyurethane, and neoprene
rubbers.
6. The apparatus of claim 2, wherein said compressive member
comprises a flexible, non-elastic membrane tensionably compressing
the breast upward toward the chest wall.
7. The apparatus of claim 6, wherein said flexible, non-elastic
membrane comprises a high-strength polyester film.
8. The apparatus of claim 1, wherein said compressive member
comprises a substantially rigid plastic having relatively high
acoustic transparency, said substantially rigid plastic being
pre-molded into a shape corresponding to a compressed breast.
9. The apparatus of claim 8, further comprising an orifice array
including said orifice and a plurality of similar orifices, each
orifice being sized differently for receiving differently-sized
breasts, each orifice having a corresponding pre-molded rigid
plastic member corresponding to a breast size for that orifice.
10. The apparatus of claim 8, wherein said substantially rigid
plastic comprises a polycarbonate plastic having a thickness in the
range of approximately 0.5 mm to 2 mm.
11. The apparatus of claim 8, said orifice and compressive member
being positioned in an approximately vertical plane to receive the
breast while the patient is in a substantially upright
position.
12. The apparatus of claim 1, said transducer comprising a first
linear array probe maintained in floatable physical contact with
said compressive member, said first linear array probe being moved
to successive positions across said compressive member while
obtaining successive ultrasound slices sufficient to reconstruct a
three-dimensional volumetric representation of the breast.
13. The apparatus of claim 1, said transducer comprising a first
linear array probe physically offset from said compressive member,
said apparatus further comprising an enclosed reservoir at least
partially defined by said frame and said compressive member, said
enclosed reservoir maintaining an acoustically conductive fluid
between said first linear array probe and said compressive member
for establishing said acoustic communication therebetween, said
first linear array probe being offsetably moved across said
compressive member while obtaining a first set of ultrasound slices
for constructing a three-dimensional volumetric representation of
the breast.
14. The apparatus of claim 13, said first linear array probe being
oriented such that said first set of ultrasound slices corresponds
to planes substantially perpendicular to a coronal plane.
15. The apparatus of claim 14, said first linear array probe being
oriented such that said first set of ultrasound slices also
corresponds to planes substantially parallel to an axillary axis
for that breast.
16. The apparatus of claim 13, said first linear array probe being
oriented such that said first set of ultrasound slices corresponds
to planes at a first skewed angle, said first skewed angle being
neither substantially parallel to nor substantially perpendicular
to said coronal plane, whereby nipple shadow effects in said
three-dimensional volumetric representation are at least partially
reduced for locations underlying a nipple of the breast.
17. The apparatus of claim 16, further comprising a second linear
array probe physically offset from said compressive member and
being offsetably moved across said compressive member while
obtaining a second set of ultrasound slices for use in constructing
said three-dimensional volumetric representation in conjunction
with said first set of ultrasound slices, said second linear array
probe being oriented such that said second set of ultrasound slices
corresponds to planes at a second skewed angle, said second skewed
angle being neither substantially parallel to nor substantially
perpendicular to said coronal plane, said second skewed angle being
substantially nonparallel to said first skewed angle, whereby
nipple shadow effects in said three-dimensional volumetric
representation are further reduced.
18. The apparatus of claim 16, said offsetable movement of said
first linear array probe having an arcuate trajectory such that
said first set of ultrasound slices corresponds to planes at a
multiplicity of skewed angles neither substantially parallel to nor
substantially perpendicular to said coronal plane, whereby nipple
shadow effects in said three-dimensional volumetric representation
are at least partially reduced.
19. The apparatus of claim 1, said orifice and compressive member
being positioned in an approximately horizontal plane to receive
the breast while the patient is in a substantially prone position,
said orifice having an oblong shape with a major axis corresponding
to an axillary axis of the patient for that breast.
20. The apparatus of claim 1, said compressive member comprising a
substantially rigid plastic having relatively high acoustic
transparency, said substantially rigid plastic having pre-molded
contours in the form of a compressed breast, said orifice having an
oblong shape with a major axis corresponding to an axillary axis of
the patient for that breast.
21. A method for scanning a breast of a patient, comprising:
receiving at least a portion of the breast through an orifice
defined by a frame, the orifice being shaped to allow at least a
portion of the breast to extend therethrough; compressing the
breast toward a chest wall of the patient using a first side of a
compressive member secured to the frame across the orifice; and
scanning the breast with a transducer positioned in acoustic
communication with a second side of the compressive member opposite
the first side of the compressive member.
22. The method of claim 21, said orifice and compressive member
being positioned in an approximately horizontal plane to receive
the breast while the patient is in a substantially prone
position.
23. The method of claim 22, wherein said compressive member
comprises a stretchable membrane elastically compressing the breast
upward toward the chest wall.
24. The method of claim 23, wherein said stretchable membrane
exerts a total upward force on the breast in the range of
approximately 2 pounds (8.9 Newtons) to 12 pounds (53.4
Newtons).
25. The method of claim 23, wherein said stretchable membrane
comprises an elastomer selected from the group consisting of:
silicone, latex, vinyl, nitrile, polyurethane, and neoprene
rubbers.
26. The method of claim 22, wherein said compressive member
comprises a flexible, non-elastic membrane tensionably compressing
the breast upward toward the chest wall.
27. The method of claim 26, wherein said flexible, non-elastic
membrane comprises a high-strength polyethylene film.
28. The method of claim 21, wherein said compressive member
comprises a substantially rigid plastic having relatively high
acoustic transparency, said substantially rigid plastic being
pre-molded into a shape corresponding to a compressed breast.
29. The method of claim 28, further comprising: identifying,
according to a size of the breast, a suitable member of an orifice
array including said orifice and a plurality of similar orifices,
each orifice being sized differently for receiving
differently-sized breasts, each orifice having a corresponding
pre-molded rigid plastic member corresponding to a breast size for
that orifice; and receiving said portion of the breast through the
identified orifice.
30. The method of claim 28, wherein said substantially rigid
plastic comprises a polycarbonate plastic having a thickness in the
range of approximately 0.5 mm to 2 mm.
31. The method of claim 28, said orifice and compressive member
being positioned in an approximately vertical plane to receive the
breast while the patient is in a substantially upright
position.
32. The method of claim 21, the transducer comprising a first
linear array probe, further comprising maintaining the first linear
array probe in floatable physical contact with the compressive
member while moving the first linear array probe across the
compressive member, the first linear array probe obtaining
ultrasound slices sufficient to reconstruct a three-dimensional
volumetric representation of the breast.
33. The method of claim 21, the transducer comprising a first
linear array probe, the frame and compressive member at least
partially defining an enclosed reservoir that maintains an
acoustically conductive fluid between the first linear array probe
and the compressive member for establishing the acoustic
communication therebetween, further comprising offsetably moving
the first linear array probe across said compressive member while
obtaining a first set of ultrasound slices for constructing a
three-dimensional volumetric representation of the breast.
34. The method of claim 33, further comprising orienting said first
linear array probe during said offsetable movement such that said
first set of ultrasound slices corresponds to planes substantially
perpendicular to a coronal plane.
35. The method of claim 34, further comprising orienting said first
linear array probe during said offsetable movement such that said
first set of ultrasound slices also corresponds to planes
substantially parallel to an axillary axis for that breast.
36. The method of claim 33, further comprising orienting said first
linear array probe during said offsetable movement such that said
first set of ultrasound slices corresponds to planes at a first
skewed angle, said first skewed angle being neither substantially
parallel to nor substantially perpendicular to said coronal plane,
whereby nipple shadow effects in said three-dimensional volumetric
representation are at least partially reduced for locations
underlying a nipple of the breast.
37. The method of claim 36, further comprising offsetably moving a
second linear array probe across said compressive member while
obtaining a second set of ultrasound slices for use in constructing
said three-dimensional volumetric representation in conjunction
with said first set of ultrasound slices, said second linear array
probe being oriented during said offsetable movement such that said
second set of ultrasound slices corresponds to planes at a second
skewed angle, said second skewed angle being neither substantially
parallel to nor substantially perpendicular to said coronal plane,
said second skewed angle being substantially nonparallel to said
first skewed angle, whereby nipple shadow effects in said
three-dimensional volumetric representation are further
reduced.
38. The method of claim 36, said offsetable movement of said first
linear array probe having an arcuate trajectory such that said
first set of ultrasound slices corresponds to planes at a
multiplicity of skewed angles neither substantially parallel to nor
substantially perpendicular to said coronal plane, whereby nipple
shadow effects in said three-dimensional volumetric representation
are at least partially reduced.
39. The method of claim 21, wherein the orifice and the compressive
member are positioned in an approximately horizontal plane to
receive the breast while the patient is in a substantially prone
position, and wherein the orifice has an oblong shape with a major
axis corresponding to an axillary axis of the patient for that
breast.
40. The method of claim 21, wherein the compressive member
comprises a substantially rigid plastic having relatively high
acoustic transparency, the substantially rigid plastic having
pre-molded contours in the form of a compressed breast, and wherein
the orifice has an oblong shape with a major axis corresponding to
an axillary axis of the patient for that breast.
41. An ultrasound scanning apparatus, comprising: a reservoir
casing holding a sonically conductive fluid and having a
substantially rigid upper surface, said upper surface having an
opening generally shaped to receive a breast of a prone patient; a
flexible membrane sealably secured across said opening, said
flexible membrane having a lower surface in contact with said
sonically conductive fluid and an upper surface pressing upward
against the breast when the breast is extended through said
opening; and a transducer disposed within said sonically conductive
fluid for imaging the breast through said flexible membrane.
42. The ultrasound scanning apparatus of claim 41, said transducer
comprising a first linear array probe, further comprising means for
translating said first linear array probe within said sonically
conductive fluid to obtain a first set of ultrasound slices
sufficient to construct a three dimensional representation of the
breast.
43. The ultrasound scanning apparatus of claim 42, wherein said
flexible membrane comprises a stretchable material that at least
partially stretches while compressing upward against the
breast.
44. The ultrasound scanning apparatus of claim 42, wherein said
flexible membrane comprises a non-elastic material that does not
stretch while compressing upward against the breast.
45. The ultrasound scanning apparatus of claim 42, further
comprising means for maintaining said first linear array probe in
floatable physical contact with said flexible membrane during said
translation of said linear probe in a manner that exerts
substantially negligible upward force on the breast.
46. The ultrasound scanning apparatus of claim 42, further
comprising means for offsetably maintaining said first linear array
probe at least 1 cm from said flexible membrane during a majority
of said linear probe translation, said first linear array probe
maintaining sonic communication with said flexible membrane through
said sonically conductive fluid.
47. The ultrasound scanning apparatus of claim 42, said first
linear array probe being oriented such that said first set of
ultrasound slices corresponds to planes substantially perpendicular
to a coronal plane.
48. The ultrasound scanning apparatus of claim 47, said first
linear array probe being oriented such that said first set of
ultrasound slices also corresponds to planes substantially parallel
to an axillary axis for that breast.
49. The ultrasound scanning apparatus of claim 42, said first
linear array probe being oriented such that said first set of
ultrasound slices corresponds to planes at a first skewed angle,
said first skewed angle being neither substantially parallel to nor
substantially perpendicular to said coronal plane, whereby nipple
shadow effects in said three-dimensional representation are at
least partially reduced for locations underlying a nipple of the
breast.
50. The ultrasound scanning apparatus of claim 49, further
comprising: a second linear array probe; means for translating said
second linear array probe within said sonically conductive fluid to
obtain a second set of ultrasound slices for use in constructing
said three dimensional representation of the breast; means for
offsetably maintaining said second linear array probe at least 1 cm
from said flexible membrane during a majority of said linear probe
translation, said second linear array probe maintaining sonic
communication with said flexible membrane through said sonically
conductive fluid, said second linear array probe being oriented
such that said second set of ultrasound slices corresponds to
planes at a second skewed angle, said second skewed angle being
neither substantially parallel to nor substantially perpendicular
to said coronal plane, said second skewed angle being substantially
nonparallel to said first skewed angle, whereby nipple shadow
effects in said three-dimensional representation are further
reduced.
51. The ultrasound scanning apparatus of claim 42, first linear
array probe having an arcuate-trajectory translation such that said
first set of ultrasound slices corresponds to planes at a
multiplicity of skewed angles neither substantially parallel to nor
substantially perpendicular to said coronal plane, whereby nipple
shadow effects in said three-dimensional representation are at
least partially reduced.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/577,388, filed Jun. 4, 2004, which is
incorporated by reference herein.
FIELD
[0002] This patent specification relates to medical ultrasound
imaging. More particularly, the present specification relates to an
apparatus and related methods for obtaining volumetric ultrasound
scans of a breast in a manner that promotes both patient comfort
and improved ultrasonic imaging of breast tissue near the chest
wall.
BACKGROUND
[0003] Volumetric ultrasound scanning of the breast has been
proposed as a complementary modality for breast cancer screening as
described, for example, in the commonly assigned US 2003/007598A1
and US2003/0212327A1, each of which is incorporated by reference
herein. Whereas a conventional two-dimensional x-ray mammogram only
detects a summation of the x-ray opacity of individual slices of
breast tissue over the entire breast, ultrasound can separately
detect the sonographic properties of individual slices of breast
tissue, and therefore may allow detection of breast lesions where
x-ray mammography alone fails. Another well-known shortcoming of
x-ray mammography practice is found in the case of dense-breasted
women, including patients with high content of fibroglandular
tissues in their breasts. Because fibroglandular tissues have
higher x-ray absorption than the surrounding fatty tissues,
portions of breasts with high fibroglandular tissue content are not
well penetrated by x-rays and thus the resulting mammograms contain
reduced information in areas where fibroglandular tissues
reside.
[0004] It is believed that preventive health care policy should
progress toward the adoption of regular breast cancer screening
procedures for increasingly younger women, for example, women under
the age of 40, and perhaps even under the age of 30 if there is a
family history of cancer. Because younger women generally have
denser breasts, the shortcomings of conventional two-dimensional
x-ray mammography are expected to become especially apparent and
lead to the increased adoption of ultrasound mammography as an
adjunctive screening modality. Even further, because the dangers of
x-ray radiation exposure are cumulative over a lifetime, ultrasound
mammography could well become a sole breast cancer screening
modality for women in these younger age groups. Other demographics
indicating higher breast densities among certain groups, regions,
or countries may also lead to the increased adoption of breast
ultrasound as a sole or adjunctive screening modality for those
groups, regions, or countries.
[0005] Criteria that can be used to characterize the effectiveness
of any particular breast ultrasound scanning method include image
quality, image resolution, volumetric completeness, repeatability,
patient comfort, per-patient costs, and patient throughput, many of
these factors being inter-related. For example, higher-frequency
ultrasound scans (e.g., 10 MHz or greater) generally yield higher
image resolution, but do so at a reduced scanning depth which can
compromise volumetric completeness of the scan. As another example,
real-time hand-held scanning of the breast by a screening
radiologist would promote volumetric completeness and patient
comfort, but would result in compromised repeatability, low patient
throughout, and high per-patient costs.
[0006] Although various automated breast ultrasound scanning
devices have been proposed, it is believed that each possesses one
or more drawbacks that make it less useful than the preferred
embodiments described herein with respect to one or more of the
above effectiveness criteria, particularly for dense-breasted
patients. For example, many proposals depend, at least in part, on
the "pendulous" properties of a breast for their effectiveness in
imaging the diagnostically relevant breast volume. Some of these
proposals require the breast to hang downwardly away from a prone
patient's body and into a chamber containing an ultrasound probe,
such as WO 02/089672 (see FIG. 1 thereof), U.S. Pat. No. 4,298,009
(see FIG. 3 thereof), and U.S. Pat. No. 6,102,866 (see FIG. 1
thereof). Others require the breast to project outwardly away from
an upright patient's body for compression between two compressive
members, an ultrasound probe scanning the breast from underneath
(WO 83/02053 at FIG. 1, U.S. Pat. No. 5,851,180 at FIG. 4A), from
the side (U.S. Pat. No. 5,479,927 at FIG. 12), or from the top
(U.S. Pat. No. 5,479,927 at FIG. 1).
[0007] The above-referenced proposals that depend, at least in
part, on the pendulous properties of the breast have limited
effectiveness with respect to at least two important aspects of
breast imaging. First, there are difficulties in imaging breast
tissue near the chest wall of the patient. Because a large number
of cancers are known to occur within 3 cm of the chest wall, this
represents a serious problem with respect to completeness of the
ultrasound screening apparatus. Second, such proposals also bring
about difficulties with small breasts, which are generally not
pendulous. For small breasts, much of the diagnostically relevant
breast tissue is physically unable to hang down into a chamber or
project outwardly onto a compression plate, thereby limiting the
completeness of the ultrasound scans.
[0008] Some proposals have been made that at least partially
address the problem of small-breasted patients. In these proposals,
a water bag or gel bag is lowered onto the breast of a supine
patient and an ultrasound probe disposed within the water bag or
gel bag scans the breast volume. Examples can be found in a
brochure by Labsonics, Inc., "Labsonics Ultrasound Breast Scanner:
Accurate, High-Performance Investigation of the Breast for
Confident Diagnosis," Mooresville, Ind. (1983), and in the commonly
assigned WO02/43801A2 at FIG. 14. However, it is believed that
substantial improvements in one or more of repeatability, patient
throughout, volumetric completeness, image quality near the chest
wall, per-patient cost, reduced shadowing effects, and even patient
comfort is provided by one or more of the preferred embodiments
described infra.
[0009] Accordingly, it would be desirable to provide a breast
ultrasound scanning apparatus and related methods that achieve
high-quality ultrasound imaging even near the chest wall of the
patient.
[0010] It would be further desirable to provide such a breast
ultrasound scanning apparatus that can imaging the entire
diagnostically relevant breast volume even for small-breasted
and/or dense-breasted patients.
[0011] It would be further desirable to provide such a breast
ultrasound scanning apparatus that is comfortable for the patient
while also having a cost-efficient patient throughput rate.
[0012] It would be still further desirable to provide a breast
ultrasound scanning apparatus that is cost-efficient to fabricate,
that obviates nipple shadow effects, and that provides
substantially repeatable scans.
SUMMARY
[0013] An apparatus and related methods for scanning a breast of a
patient are provided, the apparatus comprising (i) a frame defining
an orifice shaped to allow at least a portion of the breast to
extend therethrough, (ii) a compressive member secured to the frame
across the orifice that compresses the breast toward a chest wall
of the patient when the breast is extended through the orifice, and
(iii) a transducer positioned in acoustic communication with the
compressive member for imaging the breast therethrough. The frame
holds a reservoir of acoustically conductive fluid that maintains
the transducer in acoustic communication with the compressive
member. Preferably, the orifice has an oblong shape with a major
axis corresponding to an axillary axis of the breast.
[0014] According to one preferred embodiment, the orifice is
defined within an approximately horizontal, rigid surface of the
frame so as to receive the breast while the patient is in a
substantially prone position, and the compressive member comprises
a flexible membrane. In one preferred embodiment, the flexible
membrane comprises a stretchable material that elastically
compresses the breast upward, while in another preferred embodiment
the flexible membrane comprises a non-stretchable material that
tensionably compresses the breast upward.
[0015] According to another preferred embodiment, the compressive
member comprises a substantially rigid, acoustically conductive
plastic pre-molded into a shape corresponding to a
chestwardly-flattened breast. In this preferred embodiment, the
orifice can optionally be positioned in an approximately vertical
plane to receive the breast while the patient is in a substantially
upright position. A array of differently-sized orifices for
receiving differently-sized breasts can be provided for optimal
acoustic contact and patient comfort.
[0016] According to a preferred embodiment, the transducer is a
linear array probe that is physically offset from the compressive
member, and the linear array probe is offsetably swept across the
compressive member while obtaining a set of ultrasound sufficient
to construct a three-dimensional volumetric representation of the
breast. Alternatively, the linear array probe is maintained in
floatable physical contact with the compressive member when swept
thereacross. Preferably, the linear array probe is oriented
parallel to the axillary axis of the patient for that breast.
[0017] According to one preferred embodiment, the linear array
probe is maintained substantially perpendicular to a coronal plane
throughout the sweep. Nipple shadow effects in the
three-dimensional volumetric representation can be reduced by
sweeping an additional linear array probe having a different
scanning direction within the imaged plane across the compressive
member, and/or by using beamsteering in the linear array
probe(s).
[0018] Alternatively, nipple shadow effects can be reduced by
maintaining the linear array probe a skewed plane during the sweep,
by sweeping an additional linear array probe oriented in a
different skewed plane, and/or by sweeping the linear array
probe(s) at a multiplicity of skewed angles during an arcuate or
other irregular scanning trajectory.
[0019] Preferably, there is no additional external downward force
applied to the patient other than their natural body weight.
Patient comfort is thereby promoted while still flattening of the
breast toward the chest wall such that the required imaging depth
is substantially reduced. This, in turn, provides an ability to
higher-frequency ultrasound transducers known to result in superior
image resolution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 illustrates a perspective exterior view of a breast
scanning apparatus according to a preferred embodiment;
[0021] FIG. 2 illustrates an exploded perspective view of the
breast scanning apparatus of FIG. 1;
[0022] FIGS. 3A, 3B, and 4 illustrate a perspective view of the
breast scanning apparatus of FIG. 1 as being used by a patient;
[0023] FIG. 5 illustrates a perspective view of a breast scanning
apparatus according to a preferred embodiment as being used by a
patient;
[0024] FIGS. 6A and 6B illustrate perspective views of a breast
being compressed toward a chest wall according to a preferred
embodiment;
[0025] FIG. 7A illustrates a top view of a breast scanning
apparatus according to a preferred embodiment;
[0026] FIGS. 7B, 8, 9, 10, 11, 12, 13, and 14A illustrate
conceptual side views of chestwardly compressed breasts being
scanned using breast scanning apparatuses according to various
preferred embodiments;
[0027] FIG. 14B illustrates a top view of a breast scanning
apparatus in accordance with the preferred embodiment of FIG.
14A;
[0028] FIGS. 15A and 15B illustrate top views of a breast scanning
apparatus according to a preferred embodiment;
[0029] FIG. 16 illustrates a conceptual side view of a chestwardly
compressed breast being scanned using a breast scanning apparatus
according to a preferred embodiment; and
[0030] FIG. 17 illustrates a top view of a breast scanning
apparatus according to a preferred embodiment.
DETAILED DESCRIPTION
[0031] FIG. 1 illustrates a perspective exterior view of a breast
scanning apparatus 102 according to a preferred embodiment,
comprising a frame including a lower housing 104 and a
substantially rigid surface 106, the surface 106 defining an
orifice 107 across which is sealably secured a compressive member
in the form of a flexible membrane 108. The orifice 107 is an
opening in the surface 106 that is shaped to correspond to the
general outline of a breast of a patient, preferably including the
diagnostically important tissue near the axilla or axillary region
of the patient for that breast. For clarity of description the
scanning apparatus 102 is described herein in the context of
scanning the right breast only, it being understood that
corresponding structure is also provided for the left breast as
would be readily apparent to one skilled in the art. As indicated,
in the convention of FIG. 1, the +x direction points to the
patient's right side within the coronal plane, the +y direction
points toward the head within the coronal plane, and the +z
direction points outward toward the front of the patient in a
direction perpendicular to the coronal plane.
[0032] FIG. 2 illustrates an exploded perspective view of the
scanning apparatus 102 in which the surface 106 is removed from the
lower housing 104. The lower housing 104 and surface 106 form a
reservoir casing that maintains a sonically conductive fluid
therein. The sonically conductive fluid is not specifically drawn
in FIG. 2 but its presence is to be understood, as pointed to by
element 204. The reservoir casing formed by the lower housing 104
and surface 106 should be sufficiently filled with sonically
conductive fluid such that the flexible membrane is maintained in
bubble-free contact with the sonically conductive fluid during the
insertion of the breast through the orifice 107. A pressure/volume
relief valve system (not shown) can be provided to facilitate
proper fluid volumes within the reservoir casing during breast
insertion.
[0033] Disposed within the sonically conductive fluid 204 is a
transducer in the form of a linear array probe 210. Although a
linear array probe is generally preferred because of their
relatively low cost, it is to be appreciated that many different
kinds of 1D, 1.25 D, 1.5 D, and 2 D probes can be used without
departing from the scope of the preferred embodiments. The
sonically conductive fluid 204 can comprise water, mineral oil,
Jojoba oil, or generally any kind of couplant, gel, oil, or cream
that is acoustically conductive, substantially bubble-free, and
sufficiently nonviscous to maintain acoustic coupling between the
probe 210 and the flexible membrane 108 when the probe is in motion
without distortion of the breast contours. When the breast is
inserted into the orifice 107, the probe 210 is swept across the
frame within the sonically conductive fluid while obtaining
ultrasound slices sufficient to construct a three-dimensional
volumetric representation of the breast.
[0034] The sonically conductive fluid 204 should also be selected
with acoustic matching in mind with respect to the probe and the
compressive member, to minimize the effects of reflections. One
advantage of using a thinner membranous substance for the flexible
membrane 108 is that there is less back-and-forth reflection
between its two surfaces as compared to when a thicker material is
used as, for example, with the alternative preferred embodiments of
FIGS. 16-17, infra. Undesirable back-and-forth reflections at
surface interfaces lying between the probe and the target can cause
regularly-spaced reverberation artifacts in the resulting images.
In the cases of FIGS. 16-17, however, it has been found that using
a rigid material with a modest degree of attenuation can reduce the
reverberation artifacts, because the reverberations would die out
before causing too much harm to the resulting images.
[0035] FIGS. 3A-3B illustrates the scanning apparatus 102 as
integrated into a table 306 for receiving a breast 304 of a patient
306. The patient stands next to the table 306 and then bends over
to insert the breast 304 through the orifice 107. The breast 304 is
preferably coated with a layer of acoustic couplant prior to
insertion through the orifice 107. Alternatively or in conjunction
therewith, the flexible membrane 108 can maintain a small pool of
acoustic couplant or an be outfitted with a prefabricated couplant
sheet such as the Hydroscan Sterile Couplant Sheet available from
Cone Instruments, Inc. of Solon, Ohio.
[0036] FIG. 4 illustrates the scanning apparatus 102 as integrated
into a cot 402 for receiving the breast of the patient 302. In the
preferred embodiments of FIGS. 3 and 4, it is preferable that no
external downward forces are exerted on the breast area of the
patient other than the natural body weight of the patient. As part
of this natural body weight, the patient may be asked to mildly
urge the axilla region of the breast downward toward the orifice
107. A highly comfortable patient experience is provided while also
allowing substantially all clinically relevant breast tissue to be
imaged at a very high frequencies, e.g. 10-15 MHz and even up to 20
MHz, for patients with generally smaller breasts. However, the
scanning apparatus 102 is also operative for patients with larger
breasts as well when used according to one or more of the preferred
embodiments described further infra. Optionally, the orifice 107
may be contoured out-of-plane relative to the rest of the surface
106 to further increase patient comfort and scanning
thoroughness.
[0037] FIG. 5 illustrates a perspective view of a breast scanning
apparatus 102' according to a preferred embodiment as being used by
the patient 302 in an upright position. A C-arm and backplane
arrangement 404, or other suitable mechanical assembly, is used to
urge the scanning apparatus 102' toward the chest wall of the
patient. Preferably, the C-arm and backplane arrangement 404 is
configured to springably maintain a constant compression force that
is reminiscent of the force that would be exerted by operation of
the natural body weight of the patient if they were in a prone
position as in FIG. 3 or 4 supra. By way of example, and not by way
of limitation, a suitable range of forces may lie in the range of
approximately 2 pounds (8.9 Newtons) to 12 pounds (53.4
Newtons).
[0038] The breast scanning apparatus 102' of FIG. 5 is generally
similar to the scanning apparatus 102 of FIGS. 1-4, except that it
is preferable for the compressive member secured across the orifice
107 to comprise a rigid, acoustically conductive plastic element
pre-molded into a shape corresponding to a chestwardly-compressed
breast. This element is described further infra with respect to
FIG. 16.
[0039] FIGS. 6A and 6B illustrate perspective views, taken at
different angles from "within" the reservoir casing, of the breast
304 as it is extended into the orifice 107 and chestwardly
compressed by the flexible membrane 108. The breast 304 is urged
into a state of flattened compression generally corresponding to a
coronal plane of the patient. According to a preferred embodiment,
the total upward force exerted by the flexible membrane 108 lies in
the range of approximately 2 pounds (8.9 Newtons) to 12 pounds
(53.4 Newtons).
[0040] For patients with very small breasts, it has been found that
good results are obtained when the flexible membrane 108 comprises
a substantially inelastic material such as a 2-mil (0.051 mm) thick
sheet of Mylar.RTM. polyester film. The Mylar is secured across the
orifice 107 in a substantially taut manner such that it is roughly
coplanar with the orifice 107 itself. Even though it is
substantially inelastic, the Mylar will yield by a small amount as
it tensionably compresses the breast upward, resulting in a smooth
surface with very few gaps or wrinkles, making an ideal surface for
ultrasonically imaging the breast from underneath.
[0041] Alternatively, the flexible membrane 108 can comprise a
modestly stretchable material such as the latex, vinyl, nitrile,
polyurethane, and/or neoprene rubbers that are used in medical exam
gloves. When used in thicknesses on the orders used for medical
exam gloves (e.g., 5-15 mils=0.127-0.381 mm) suitable compression
of the breast can be experienced with tolerable amounts (e.g., on
the order of 3 dB or less) of attenuation. Silicone rubber on the
order of 5-15 mils (0.127-0.381 mm) can also be used. Similarly
performing materials can be used without departing from the scope
of the preferred embodiments. The stretchable material causes the
flexible membrane 108 to elastically compress the breast upward,
which results in a smooth surface with very few gaps or wrinkles
while also promoting patient comfort. Generally speaking, higher
degrees of stretchability are desired as the breast size increases,
for promoting patient comfort while still providing substantial
chestward compression, minimization of wrinkles/gaps in the
material, and minimization of skin folds at the breast
periphery.
[0042] FIG. 7A illustrates a top view of a breast scanning
apparatus 702 according to a preferred embodiment that is similar
to that of scanning apparatus 102 of FIG. 2, except that a linear
probe 710 is oriented along an axillary axis and swept in a
direction perpendicular thereto. As used herein, axillary axis
generally refers to an imaginary line extending roughly from the
nipple to the axilla of the breast. The preferred embodiment of
FIG. 7A has a particular advantage brought about by a known
characteristic of linear array probes. In particular, a
three-dimensional volumetric representation built from raw
ultrasound slices obtained by a swept linear array probe will have
generally superior resolution in planes parallel to the raw
ultrasound slices, and generally inferior resolution in planes
perpendicular to the raw ultrasound slices along the direction of
the probe sweep. This is generally an outgrowth of a spatial
integration effect that occurs along the elevation beamwidth of
linear array probes. Advantageously, MLO thick-slice images
computed by integrating the raw ultrasound slices captured parallel
to the axillary axis according to the preferred embodiment of FIG.
7A will generally be of superior quality.
[0043] FIG. 7B illustrates a conceptual side view of the
chestwardly compressed breast 304 being scanned in accordance with
the preferred embodiment of FIG. 7A. The flexible membrane 108
compresses the breast 304 upward toward a chest wall 714 such that
a maximum distance "d" between the flexible membrane 108 and the
chest wall 714, i.e. the required ultrasonic penetration depth, is
usually no more than 2-3 cm for small-sized breasts. This allows
very high probe frequencies to be used for greater image resolution
as may be harnessed, for example, for the visual and/or
computer-assisted detection (CAD) of microcalcifications in the
three-dimensional breast volume. Even for larger-sized breasts the
distance "d" has been found to be relatively modest due to lateral
spreading of the breast.
[0044] Also shown in FIG. 7B is some non-breast tissue 712 on the
anterior side of the chest wall 714 and interior non-breast tissue
716 in the posterior side of the chest wall 714. As indicated in
FIG. 7B, the sonically conductive fluid 204 maintains acoustic
communication between the linear probe 710 and the flexible
membrane 108 as the probe is offsetably translated across the face
of the breast. Small gaps that may occur near an orifice 107
boundary are found to be generally filled in by the acoustic
couplant pool and/or prefabricated couplant sheet described supra
with respect to FIGS. 3A-3B. Alternatively, even if some of these
small gaps remain, their negative effects can be controlled by the
effects of the skewed orientations and trajectories described
infra, and/or by beamsteering, that also obviate nipple-shadow
effects.
[0045] FIG. 8 illustrates a conceptual side view of the chestwardly
compressed breast 304 being scanned in accordance with a preferred
embodiment designed to minimize the occurrence of nipple shadow
that could be caused by nipple 305. A first linear probe 810a is
skewed relative to both (i) the coronal plane, and (ii) a plane
perpendicular to the coronal plane, while a second linear probe
810b is skewed relative to (i) the coronal plane, and (ii) the
plane perpendicular to the coronal plane, and (iii) the plane of
the first linear probe 810a. The skew angle can be anywhere from
15-75 degrees depending on the particular implementation, with one
particularly useful skew angle being near 45 degrees. When
compounded to form the three-dimensional volume using principles
known in the art, the effects of nipple shadow are reduced in
comparison to the scenario of FIG. 7B.
[0046] FIG. 9 illustrates a conceptual side view of the chestwardly
compressed breast 304 being scanned in accordance with another
preferred embodiment, wherein a single linear probe 910 is swept in
a circularly-shaped trajectory 912. When individual ultrasound
frames are compounded to form the three-dimensional volume, nipple
shadow effects are also reduced in comparison to the scenario of
FIG. 7B. FIG. 10 illustrates a conceptual side view of the
chestwardly compressed breast 304 being scanned in accordance
another preferred embodiment, wherein a single linear probe 1010 is
swept in a cam follower-like trajectory 1012, with similar nipple
shadow reduction effects.
[0047] FIG. 11 illustrates a conceptual side view of the
chestwardly compressed breast 304 being scanned in accordance with
another preferred embodiment, wherein a single linear probe 1110
maintains floatable contact with the flexible membrane 108 during
the probe sweep. Means for translating the linear probe 1110 in
such a floatable fashion can be used that are analogous to those
described, albeit in different contexts, in U.S. Pat. No. 6,574,499
and JP2003310614A2, each of which is incorporated by reference
herein.
[0048] FIGS. 12 and 13 illustrate conceptual side views of the
chestwardly compressed breast 304 being scanned in accordance with
preferred embodiment designed to minimize the occurrence of nipple
shadow. In these preferred embodiments, a plurality of linear
probes 1210a/1210b and 1310a/1310b/1310c, respectively, lie in a
common plane but are oriented at different directions within that
common plane. The common plane can be perpendicular to, or skewed
relative to, the coronal plane. For clarity of description, the
trajectory of the linear probe assembly is "into" the paper in
FIGS. 12 and 13. The ultrasound slices are first compounded in a
planar fashion for a given probe assembly location, then assembled
into the desired three-dimensional volumetric representation.
Instead of tilting the probe segments 1210a/1210b and 1310a/1310c,
in-plane beamsteering using a straight horizontal multiple-segment
probe assembly can alternatively be used to achieve similar
nipple-shadow reduction results.
[0049] FIG. 14A illustrates a conceptual side view of the
chestwardly compressed breast 304 being scanned in accordance with
another preferred embodiment, wherein a single linear probe 1410 is
rotated about an axis perpendicular to the coronal plane while
capturing ultrasound slices in planes also perpendicular to the
coronal plane. FIG. 14B illustrates a top view of the apparatus of
FIG. 14A. Instead of tilting the linear probe 1410, in-plane
beamsteering using a horizontally-oriented probe can alternatively
be used to achieve similar nipple-shadow reduction results.
[0050] FIGS. 15A and 15B illustrate a top view of a breast
ultrasound scanning apparatus 1502 having two linear probes 1510
and 1511 with orthogonal trajectories in the x-y plane. Image
quality of the resultant compounded three-dimensional
representation is enhanced, with lower resolutions in the elevation
beamwidth direction of one probe being compensated by the higher
in-plane resolution of the other probe for both the x and y
directions. In an alternative preferred embodiment, with reference
to FIG. 7A supra, the two scanning directions are parallel to the
axillary axis and perpendicular to the axillary axis,
respectively.
[0051] FIG. 16 illustrates a conceptual side view of the
chestwardly compressed breast 304 being scanned while compressed
against a substantially rigid compressive member 1608. The
compressive member 1608 comprises a rigid, acoustically conductive
plastic element pre-molded into a shape corresponding to a
chestwardly-compressed breast. This preferred embodiment has an
advantage in that the breast scanning apparatus can be tilted at
different angles, e.g., in the vertical orientation of FIG. 5,
supra, such tilting being generally more difficult for
flexibly-membraned orifices due to vertical fluid pressure
variations.
[0052] FIG. 17 illustrates a top view of a breast scanning
apparatus 1702 comprising an array of orifices 1707a-1707d and
associated substantially rigid compressive members 1708a-d,
respectively, each being similar to that of FIG. 16 except having
differing sizes. According to a preferred embodiment, the medical
clinician selects the properly-sized orifice according to the size
of patient's breast prior to the scan. One example of suitable
material for the substantially rigid compressive members
1608/1708a-d is polycarbonate plastic having a thickness in the
range of approximately 0.5 mm to 2 mm. However, other materials of
similar rigidity and sonolucence can be used, for example,
polymethylpentene (PMP), which is also known by the trade name of
TPX plastic. Among other advantages, a breast ultrasound scanner
according to the preferred embodiments is robust against breathing
motion by the patient during the sweep of the ultrasound probe. As
best appreciated with respect to FIG. 7B, breathing action by the
patient has minimal impact on the probe-to-tissue distance, which
is substantially fixed by abutment of the orifice 107 against the
chest wall 714 (through the small amount of skin/tissue 712).
Instead, the breathing action mainly affects vertical movement of
the patient at internal tissues 716 (which includes the lungs),
this tissue lying above the chest wall 714.
[0053] Preferably, a breast ultrasound scanner according to the
preferred embodiments is further equipped to facilitate
identification of the nipple position in the acquired
three-dimensional volumes. In a simplest preferred embodiment, the
nipple position may be identified manually by the technician at the
time of scanning, e.g., by ensuring that the nipple falls on a
predetermined point on the compression plate. In another preferred
embodiment, the technician can interact with the scanning system
based on a quick exploratory sweep across the breast by the probe,
followed by a manual selection (such as by a mouse click) on a
display of the observed position of the nipple. In another
preferred embodiment, the technician can manually position the
center of the ultrasound probe (e.g., by joystick control) to the
nipple location and press a nipple identification button, thereby
identifying the nipple location within the subsequent
three-dimensional scans. Any of a variety of other nipple
identification schemes can be used without departing from the scope
of the preferred embodiments.
[0054] Whereas many alterations and modifications of the present
invention will no doubt become apparent to a person of ordinary
skill in the art after having read the foregoing description, it is
to be understood that the particular embodiments shown and
described by way of illustration are in no way intended to be
considered limiting. Therefore, reference to the details of the
preferred embodiments are not intended to limit their scope, which
is limited only by the scope of the claims set forth below.
* * * * *