U.S. patent application number 14/339712 was filed with the patent office on 2014-12-11 for systems and methods for synthetic aperture ultrasound tomography.
This patent application is currently assigned to LOS ALAMOS NATIONAL SECURITY, LLC. The applicant listed for this patent is Los Alamos National Security, LLC. Invention is credited to Lianjie Huang.
Application Number | 20140364734 14/339712 |
Document ID | / |
Family ID | 48905935 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140364734 |
Kind Code |
A1 |
Huang; Lianjie |
December 11, 2014 |
SYSTEMS AND METHODS FOR SYNTHETIC APERTURE ULTRASOUND
TOMOGRAPHY
Abstract
Synthetic-aperture ultrasound tomography systems and methods
using scanning arrays and algorithms configured to simultaneously
acquire ultrasound transmission and reflection data, and process
the data for improved ultrasound tomography imaging.
Inventors: |
Huang; Lianjie; (Los Alamos,
NM) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Los Alamos National Security, LLC |
Los Alamos |
NM |
US |
|
|
Assignee: |
LOS ALAMOS NATIONAL SECURITY,
LLC
Los Alamos
NM
|
Family ID: |
48905935 |
Appl. No.: |
14/339712 |
Filed: |
July 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US2013/024539 |
Feb 3, 2013 |
|
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14339712 |
|
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61594865 |
Feb 3, 2012 |
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Current U.S.
Class: |
600/447 |
Current CPC
Class: |
A61B 8/14 20130101; A61B
8/085 20130101; A61B 8/15 20130101; A61B 5/7275 20130101; G01S
15/8915 20130101; A61B 8/13 20130101; G01S 15/8929 20130101; A61B
8/483 20130101; A61B 5/0073 20130101; A61B 8/4477 20130101; A61B
8/5207 20130101; G06T 5/001 20130101; A61B 8/4494 20130101; A61B
8/4488 20130101; A61B 8/406 20130101; G06T 11/005 20130101; A61B
8/0825 20130101; G01S 15/8997 20130101; A61B 8/145 20130101 |
Class at
Publication: |
600/447 |
International
Class: |
A61B 8/13 20060101
A61B008/13; A61B 5/00 20060101 A61B005/00; A61B 8/08 20060101
A61B008/08 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] This invention was made with Government support under
Contract No. DE-AC52-06NA25396 awarded by the Department of Energy.
The Government has certain rights in the invention.
Claims
1. A synthetic aperture ultrasound tomography imaging system for
imaging a tissue medium, comprising: one or more ultrasound
transducer arrays; the one or more ultrasound transducer arrays
comprising a plurality of transducers; wherein the plurality of
transducers are configured such that a first set of two or more
transducers are positioned at an opposing spaced-apart orientation
from a second set of two or more transducers such that the first
set of two or more transducers face the second set of two or more
transducers; wherein the first and second sets of two or more
transducers are positioned at spaced-apart locations so as to allow
for the tissue medium to be positioned in between the first and
second sets of two or more transducers; a processor; and
programming executable on said processor and configured for:
exciting a first transducer within the first set of two or more
transducers to generate an ultrasound field within the tissue
medium; and receiving a transmission signal and a reflection signal
from at least the second set of two or more transducers.
2. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the programming is configured for
receiving a reflection signal from all transducers in the one or
more arrays.
3. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the programming is configured for
simultaneously receiving the reflection and transmission signals
from the second set of two or more transducers.
4. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the programming is configured for
generating an ultrasound waveform tomography image reconstruction
using both the acquired reflection and transmission signals.
5. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the one or more ultrasound transducer
arrays comprises: a first array of transducers comprising the first
set of two or more transducers; and a second array of transducers
comprising the second set of two or more transducers; wherein the
first array of transducers is positioned at spaced-apart opposing
locations.
6. A synthetic aperture ultrasound tomography imaging system as
recited in claim 5, wherein both the first array of transducers and
second array of transducers comprise linear arrays.
7. A synthetic aperture ultrasound tomography imaging system as
recited in claim 5, wherein at least one of the first array of
transducers and the second array of transducers comprises a
curvilinear array.
8. A synthetic aperture ultrasound tomography imaging system as
recited in claim 7, wherein the first array of transducers
comprises a linear array and the second array of transducers
comprises a curvilinear array.
9. A synthetic aperture ultrasound tomography imaging system as
recited in claim 8, wherein the first array of transducers
comprises a 2-D planar array and the second array of transducers
comprises a 2-D curvilinear array.
10. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1: wherein the one or more ultrasound transducer
arrays comprises an arcuate array; and wherein the first and second
sets of two or more transducers comprise the arcuate array.
11. A synthetic aperture ultrasound tomography imaging system as
recited in claim 10, wherein the arcuate array comprises a first
1-D circular array.
12. A synthetic aperture ultrasound tomography imaging system as
recited in claim 11, wherein the arcuate array comprises a 2-D
cylindrical array.
13. A synthetic aperture ultrasound tomography imaging system as
recited in claim 11, further comprising a second 1-D circular array
positioned concentrically and at a spaced-apart location with the
first 1-D circular array.
14. A synthetic aperture ultrasound tomography imaging system as
recited in claim 13: wherein the second 1-D circular array
comprises a third set of two or more transducers; and wherein the
programming is configured for receiving a transmission signal and a
reflection signal from at least the third set of two or more
transducers.
15. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the plurality of transducers comprise
an arcuate surface for generating a diverging ultrasound field
within the tissue medium.
16. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the one or more arrays of transducers
are configured to translate with respect to the tissue medium.
17. A synthetic aperture ultrasound tomography imaging system as
recited in claim 1, wherein the one or more arrays of transducers
are configured to be positioned in a submersible tank, said tank
configured to allow the tissue medium to hang pendent between the
first and second sets of two or more transducers.
18. A synthetic aperture ultrasound tomography imaging method for
imaging a tissue medium with one or more ultrasound transducer
arrays comprising a plurality of transducers, comprising: exciting
a first transducer within the plurality of transducers to generate
an ultrasound field within the tissue medium; and receiving a
transmission signal and a reflection signal from a second
transducer within the one or more ultrasound transducer arrays.
19. A synthetic aperture ultrasound tomography imaging method as
recited in claim 18: wherein the plurality of transducers are
configured such that a first set of two or more transducers are
positioned at an opposing spaced-apart orientation from a second
set of two or more transducers such that the first set of two or
more transducers face the second set of two or more transducers;
wherein the first and second sets of two or more transducers are
positioned at spaced-apart locations so as to allow for the tissue
medium to be positioned in between the first and second sets of two
or more transducers; and wherein the method further comprises:
exciting a first transducer within the first set of two or more
transducers to generate an ultrasound field within the tissue
medium; and receiving a transmission signal and a reflection signal
from at least the second set of two or more transducers.
20. A synthetic aperture ultrasound tomography imaging method as
recited in claim 19, further comprising receiving a reflection
signal from all transducers in the one or more arrays.
21-39. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 35 U.S.C. .sctn.111(a) continuation of
PCT international application number PCT/US2013/024539 filed on
Feb. 3, 2013, incorporated herein by reference in its entirety,
which claims priority to, and the benefit of, U.S. provisional
patent application Ser. No. 61/594,865, filed on Feb. 3, 2012,
incorporated herein by reference in its entirety. Priority is
claimed to each of the foregoing applications.
[0002] The above-referenced PCT international application was
published as PCT International Publication No. WO 2013/116807 on
Aug. 8, 2013, incorporated herein by reference in it entirety.
INCORPORATION-BY-REFERENCE OF COMPUTER PROGRAM APPENDIX
[0004] Not Applicable
NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION
[0005] A portion of the material in this patent document is subject
to copyright protection under the copyright laws of the United
States and of other countries. The owner of the copyright rights
has no objection to the facsimile reproduction by anyone of the
patent document or the patent disclosure, as it appears in the
United States Patent and Trademark Office publicly available file
or records, but otherwise reserves all copyright rights whatsoever.
The copyright owner does not hereby waive any of its rights to have
this patent document maintained in secrecy, including without
limitation its rights pursuant to 37 C.F.R. .sctn.1.14.
BACKGROUND OF THE INVENTION
[0006] 1. Field of the Invention
[0007] This invention pertains generally to imaging, and more
particularly to ultrasound imaging using a synthetic aperture
ultrasound ray tomography and ultrasound waveform tomography.
[0008] 2. Description of Related Art
[0009] Breast cancer is the second-leading cause of cancer death
among
[0010] American women. The breast cancer mortality rate in the U.S.
has been flat for many decades, and has decreased only about 20%
since the 1990s. Early detection is the key to reducing breast
cancer mortality. There is an urgent need to improve the efficacy
of breast cancer screening. Ultrasound tomography is a promising,
quantitative imaging modality for early detection and diagnosis of
breast tumors.
[0011] Ultrasound waveform tomography is gaining popularity, but is
computationally expensive, even for today's fastest computers. The
computational cost increases linearly with the number of
transmitting sources.
[0012] Synthetic-aperture ultrasound has great potential to
significantly improve medical ultrasound imaging. In a synthetic
aperture ultrasound system, ultrasound from each element of a
transducer array propagates to the entire imaging domain, and all
elements in the transducer array receive scattered signals.
[0013] Many conventional ultrasound systems record only 180.degree.
backscattered signals. Others are configured to receive only
transmission data from the scanning arrays. Accordingly, these
systems suffer from extensive computational costs, insufficient
resolution, or both.
BRIEF SUMMARY OF THE INVENTION
[0014] The system and method of the present invention uses
ultrasound data acquired using a synthetic-aperture ultrasound
system. The investigational synthetic-aperture ultrasound
tomography system of the present invention allows acquisition of
each tomographic slice of patient ultrasound data in real time. In
the system, each element of the transducer array transmits
ultrasound sequentially, and elements in the transducer array
simultaneously record ultrasound signals scattered from the tissue
after each element is fired. The features of the system and method
of the present invention provide a real-time synthetic-aperture
system that can be used for patient data acquisition.
[0015] In the synthetic-aperture ultrasound tomography system of
the present invention, ultrasound from each element of a transducer
array or a virtual source of multiple elements propagates to the
entire imaging domain, and all elements in the transducer array
receive ultrasound signals reflected/scattered from the imaging
region and/or transmitted/scattered through the imaging region.
Therefore, the acquired synthetic-aperture ultrasound data contain
information of ultrasound reflected/scattered and transmitted from
all possible directions from the imaging domain to the transducer
array to generate a more accurate, 3-D, high resolution image,
while minimizing computational costs of the system.
[0016] Further aspects of the invention will be brought out in the
following portions of the specification, wherein the detailed
description is for the purpose of fully disclosing preferred
embodiments of the invention without placing limitations
thereon.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0017] The invention will be more fully understood by reference to
the following drawings which are for illustrative purposes
only:
[0018] FIG. 1 is a schematic diagram of a synthetic-aperture
ultrasound system in accordance with the present invention.
[0019] FIG. 2 is a schematic diagram of a synthetic-aperture
ultrasound tomography system for scanning breast tissue in
accordance with the present invention
[0020] FIG. 3 is a schematic diagram of the scanner of the
ultrasound tomography system of FIG. 1 interrogating a region of
tissue.
[0021] FIG. 4 shows flow diagram of a method for sequentially
exciting a region of tissue and acquiring reflection and
transmission data in accordance with the present invention.
[0022] FIG. 5 illustrates a schematic view of a two parallel-bar
ultrasound transducer array scanner.
[0023] FIG. 6 illustrates a schematic view of a scanner comprising
two parallel planar arrays.
[0024] FIG. 7 shows a schematic view of a cylindrical array scanner
having a cylindral 2-D array of transducers and a 2-D planner array
at the bottom of the cylinder.
[0025] FIG. 8 shows a flat transducer configured to generate a
collimated beam.
[0026] FIG. 9 shows an arcuate transducer configured to generate a
diverging beam.
[0027] FIG. 10 shows a schematic view of a a torroidal array
scanner having a a circular array of transducers.
[0028] FIG. 11 shows a schematic view of a synthetic-aperture
ultrasound breast tomography scanner that incorporates use of two
circular transducer arrays.
[0029] FIG. 12 shows a schematic view of a scanner comprising a
semicircular or arcuate array having transducers in an opposing or
facing orientation with planar array.
[0030] FIG. 13 illustrates a scanner that reduces the 2D arrays in
FIGS. 12 to 1D arrays.
[0031] FIG. 14 is a flow diagram of a synthetic aperture ultrasound
tomography method in accordance with the present invention.
[0032] FIG. 15 shows an image of a numerical breast phantom
containing two different tumors.
[0033] FIG. 16A and FIG. 16B show imaging results (tomographic
reconstruction in FIG. 16A, and vertical profile along the center
of the tumors in FIG. 16B) obtained using only the reflection
data.
[0034] FIG. 17A and FIG. 17B show imaging results (tomographic
reconstruction in FIG. 17A, and vertical profile along the center
of the tumors in FIG. 17B) obtained using only the transmission
data.
[0035] FIG. 18A and FIG. 18B show imaging results (tomographic
reconstruction in FIG. 18A, and vertical profile along the center
of the tumors in FIG. 18B) obtained using both transmission and
reflection data simultaneously in accordance with method of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The description below is directed to synthetic aperture
ultrasound tomography systems for imaging a medium such patient
tissue, along with ultrasound waveform tomography methods for
acquiring and processing data acquired from these systems, or other
systems that may or may not be available in the art.
[0037] The synthetic-aperture breast ultrasound tomography system
of the present invention uses synthetic-aperture ultrasound to
obtain quantitative values of mechanical properties of breast
tissues. In this system, each transducer element transmits
ultrasound waves sequentially, and when an ultrasound transducer
element transmits ultrasound waves propagating through the breast,
all ultrasound transducer elements (at least within a portion of an
array) simultaneously receive ultrasound reflection/transmission,
or forward and backward scattering signals. The ultrasound
reflection/transmission signals are used to obtain quantitative
values of mechanical properties of tissue features (and in
particular breast tumors), including the sound speed, density, and
attenuation.
[0038] While the systems and methods described below are
particularly directed and illustrated for imaging of breast
tissues, it is appreciated that the systems and methods may also be
employed for waveform tomography on other tissues or scanning
mediums.
[0039] I. Synthetic Aperture Ultrasound Tomography System
[0040] FIG. 1 is a schematic diagram of a synthetic-aperture
ultrasound system 10 in accordance with the present invention. The
system 10 includes a scanner 12 comprising a plurality of
individual transducer elements 16 disposed within one or more
arrays (e.g. the opposing parallel arrays 14a and 14b shown in FIG.
1). The scanner 12 is coupled to a server or like computing
apparatus 20 (e.g. with a cable 15 or other connection means such
as, but not limited to, a wireless connections means) and synthetic
aperture ultrasound data acquisition system 18 that outputs RF data
28 corresponding to readings acquired by the scanner 12.
[0041] The computer 20 comprises a processor 24 configured to
operate one or more application programs 22 located within memory
25, wherein the application programs 22 may contain one or more
algorithms or methods of the present invention for imaging a tissue
medium for display via a graphical user interface 23 on monitor 26,
or other means. For example, the application programming 22 may
comprise the programming configured for operating the sequential
excitation method 50 shown in FIG. 4 or ultrasound waveform
tomography imaging method 200 shown in FIG. 14. The computer 20
controls ultrasound tomography data acquisition, and the process is
completed automatically. The whole-breast scanning time with
approximately 100 slides takes approximately 2 minutes.
[0042] FIG. 2 is a schematic view of a breast ultrasound tomography
system 11 in accordance with the present invention. System 11
includes a table 70 having a water tank 76 with an open aperture at
the top of the table 70 for insertion of the patient's breast
tissue (which ideally hangs pendant within water tank 76 during
imaging). Tank 76 includes one or more synthetic-aperture
ultrasound transducer arrays 74 located within one or more surfaces
of the tank. The transducer array(s) 74 are immersed within the
water tank 76 configured for receiving the patients breast 44
through aperture 72, and scanning the breast 44 while the patient
is lying down on the table 70 in the prone position. As described
in further detail below, transducer array(s) 74 may comprise a
number of different configurations, with the water tank housing 76
shaped accordingly to house the array(s) 74. The water tank housing
76 material preferably comprises a light, non-conductive material
that conforms to the shape of the array(s) 74 (e.g. rectangular for
2-parallel bar array scanner 12 of FIG. 1, or cylindrical for the
scanners 110, 120 and 130 shown in FIG. 7, FIG. 10 and FIG. 11,
respectively).
[0043] Positioning of the active areas of all array(s) 74 relative
to the water tank housing 76 is preferably aligned such that the
ultrasound energy for the transducer elements 16 (FIG. 1) is
focused onto the same plane perpendicular to the housing (for
parallel bar scanner 12 (FIG. 5) or planar 100 (FIG. 6) arrays).
The arrays (e.g. arrays 14a and 14b, FIG. 1) are preferably
electrically isolated and grounded.
[0044] The system 11 includes a data acquisition system 18 that may
be coupled to a computer system or electronics 78 that control
scanning. The data acquisition system 18 may also be coupled to a
computer 20 for running application programming 22 (FIG. 1) to
perform tomography reconstructions.
[0045] During the ultrasound data acquisition in the
synthetic-aperture ultrasound tomography system 10, the raw
ultrasound data 28 (radio-frequency data) may be first stored
within computer memory 25 (FIG. 1) (which may comprise solid state
drives or other storage means available in the art), allowing
real-time patient data acquisition for clinical applications.
[0046] FIG. 3 is a schematic diagram of the two parallel bar arrays
14a and 14b of scanner 12 of FIG. 1 shown interrogating a region of
tissue 44 (e.g. breast tissue for mammography) in accordance with a
preferred method of the present invention. The ultrasound imaging
system 10 focuses an array 14a and 14b of N transducers 16 acting
in a transmit-receive mode. Each element of the array 14a 14b is
excited sequentially (e.g. transducer 3 of array 14a is shown in
excitation mode) to generate an ultrasound field or signal 30
through the tissue surface 40 and into tissue medium 44 having a
plurality of point scatterers 42. The backscattered signals 32 are
measured in parallel by all N elements 16. In addition, opposing
array 14b transducers are positioned facing array 14a such that one
or more elements of the array 14b receive direct transmission
signals 30 simultaneously with reception of backscatter or
reflection signals 32 being received by array 14a.
[0047] FIG. 4 shows flow diagram of a method 50 for sequentially
exciting a region of tissue 44 in accordance with the present
invention. At step 52, a first element (e.g. element 1 or i) of
array 14a 14b of N ultrasound transducer elements 16 is excited for
interrogating an inhomogeneous medium 44. At step 54, the
backscattered/reflected signals 32 are received/measured by all
elements 16 (of at least 14a), while transmission signals 30 are
received/measured by one or more elements 16 of array 14b. At step
58, the method evaluates whether all the elements 16 in the arrays
14a and 14b have been excited (and imaged). If the last element in
the arrays 14a, 14b has not been reached, the method moves to the
next element 16 in the array (14a or 14b) at step 60, and repeats
the process sequentially until the N.sup.th element is reached. At
this point, the individual reflection/transmission data are RF
data, and the process 50 transfers the RF data to memory or solid
state drives 25 at step 64.
[0048] In the phased transducer arrays for synthetic-aperture
breast ultrasound tomography, a plurality of transducer elements 16
are fired with different delayed times to simulate ultrasound waves
emerging from a virtual point source. The systems and methods of
the present invention preferably use the virtual point sources of
the synthetic-aperture breast ultrasound tomography system to
improve signal-to-noise ratios of breast ultrasound data.
[0049] The various scanning arrays invention, described below with
reference to FIG. 5 through FIG. 7 and FIG. 10 through FIG. 13, are
shown to illustrate that the systems 10, 11 and methods 50, 200 may
be achieved in various configurations. Yet, the scanning arrays of
FIG. 5 through FIG. 7 and FIG. 10 through FIG. 13 all share at
least one common characteristic in that at a plurality of
transducers 16 of an array, or portion of an array, oppose (at a
spaced-apart distance across the target scanning medium 44) a
plurality of transducers 16 of either another portion of the array,
or a separate array, so that reflection and transmission data may
be acquired with each successive transducer excitation. The
following are specific examples of arrays that may be used in the
systems 10, 11 and methods 50, 200 of the present invention.
However, other configurations are contemplated. In each of these
configurations, the scanner 74 is shown without table 70 or housing
76 for clarity.
[0050] A. Dual Parallel-Bar Array Scanner
[0051] FIG. 5 illustrates a two parallel-bar ultrasound transducer
array scanner 12, which is illustrated in reference to
implementation within system 10 in FIG. 1, and schematically in
operation as a synthetic-aperture scanner in FIG. 3.
[0052] As shown in FIG. 5, the two arrays 14a and 14b are shown in
opposing orientation (e.g. facing each other and matching in
location along x-axis in FIG. 5), and positioned in the x-y plane
(preferably parallel to table 70 in FIG. 2, such that they are
spaced-apart across the scanning region 44. Each of the 14a and 14b
comprises a plurality of N transducers 16 (e.g. count of 128)
linearly aligned in series (shown in along the x-axis for
reference) as parallel-phased arrays firing toward each other in
operation (see FIG. 3).
[0053] A robotic stage 90 is provided so that the arrays can move
in unison vertically along the z-axis to scan the tissue 44. The
transducer arrays 14a and 14b are configured to scan the breast 44
from the chest wall to the nipple region, slice by slice. To image
the axillary region (region of breast closest to the armpit of the
patient, not shown), the two transducer arrays 14a and 14b can be
steered toward the axillary region, with one of the the transducer
arrays placed near the axillary region. The axillary region, or
basin, is important to oncologic surgeons, as it represents the
principal lymphatic drainage region of the breast. Lymphatic
metastasis from a malignant breast lesion will most often occur in
this region.
[0054] Arrays 14a and 14b may also be translated (either in
concert, or with respect to each other) in the x and y axes to
closely conform to varying patient anatomy.
[0055] Referring to FIG. 8 and FIG. 9, the transducer 16 may either
be flat or circular, and the surface of the transducer element 16
may either be flat, as in transducer 16a in FIG. 8, or arcuate in
shape, as shown in transducer 16b of FIG. 9. The flat transducer
16a of FIG. 8 generates a collimated beam 17, whereas the
curvilinear transducer 16b of FIG. 9 has a focal point P that is
behind the emitting surface to generate a diverging beam 19
(defocused or lens configuration preferably in the y-z plane)
across a field of view from A to B (centered on C). The curvilinear
transducer 16b of FIG. 9 helps get a 3-D volume while scanning, and
is particularly useful with line arrays such as those in FIG. 5,
FIG. 10, FIG. 11, and FIG. 13.
[0056] In one embodiment, exemplary dimensions for the arrays 14a
and 14b and transducers 16 are as follows: a length inside the
water tank along X-axis (the horizontal direction) of 16 inches,
with 19.2 inches along Y-axis (the horizontal direction) and 16
inches in height along Z-axis (the vertical direction). The
distances from the ends of the ultrasound phased transducer arrays
14a and 14b to the inside walls of the water tank along X-axis are
approximately 3.8425 inches. In one embodiment, the horizontal
distance between the front surfaces of the two parallel phased
ultrasound transducer arrays can be adjusted from 12 cm to 25 cm,
with a 1 cm increment utilizing 14 different sets of spacer blocks.
The accuracy and precision of the horizontal position is ideally 5
microns or better. The vertical travel (Z axis) of the two parallel
ultrasound phased transducer arrays 14a and 14b is 10 inches from
the top surface of the water level. The vertical travel step
interval can be adjusted to any value, such as 0.25 mm, 0.5 mm, 1
mm, and 2 mm.
[0057] In one embodiment, array 14a, 14b parameters are as follows:
center frequency of 1.5 MHz, bandwidth of .about.80% bandwidth (-6
dB) (measured for two-way sound propagation energy), the open angle
of ultrasound waves emitting from a single element at
.about.80.degree., with uniform transducer elements 16 (<1 dB
variation, and uniform bandwidth for one-way sound propagation
energy).
[0058] In one embodiment, the arrays 14a, 14b comprise 1.5 MHz
arrays with 384 elements each, equally spaced along the array. In
one example, the dimensions/characteristics of the transducer
elements are as follows: elevation aperture: 15 mm, element width:
0.4 mm for 1.5 MHz arrays, elevation focus: 10 cm away from the
transducer element, with all transducers configured to be aligned
along the array and perpendicular to the elevation plane.
[0059] It is appreciated that the above dimensions and
configuration details are for reference purposes only, and such
characteristics may be varied accordingly.
[0060] The advantage of the configuration of scanner 12, over, e.g.
the planar arrays of FIG. 6, is that the system 10 is using a fewer
number of transducer elements.
[0061] B. Dual Parallel Planar Array Scanner
[0062] FIG. 6 illustrates a scanner 100 comprising two parallel
planar arrays 102a and 102b aligned opposing each other across the
scanning medium 44. Arrays 102a and 102b each comprise matching
grids of 2-D arrays of transducers 16 (e.g. transducers 16 share
the same locations in their respective x-z planes shown in FIG. 6).
With the planar arrays the scanner 100 generally does not need to
be translated in the z (vertical) direction.
[0063] There are generally two limitations for the
synthetic-aperture breast ultrasound tomography with the
cylindrical or circular transducer arrays: (a) it is difficult to
image the axillary region of the tissue 44; and (b) one size of the
cylindrical or circular transducer array will either be undersized
or oversized for most sizes of the breast.
[0064] Synthetic-aperture breast ultrasound tomography with two
parallel planar ultrasound transducer arrays 102a and 102b can
overcome these two limitations. As shown in FIG. 6, one planar/2D
transducer array 102b can be placed close to the axillary region of
the tissue 44. In addition, the distance between the two planar
ultrasound transducer arrays 102a and 102b can be adjusted with
respect to each other (either manually or with robotic stage 90 as
shown in FIG. 5) to fit different sizes of the breast. The
ultrasound transducer elements 16 can be in circular or rectangular
shape, and the surface of the transducer element can be either flat
or arc-shaped, as shown in FIG. 8 and FIG. 9.
[0065] C. Cylindrical Array Scanner
[0066] FIG. 7 shows a cylindrical array scanner 110 having a
cylindrical 2-D array 112a of transducers 16 in the inside surface
of the cylinder wall 118 of the ultrasound transducer array. A
planar array of elements 112b may also be positioned on the bottom
surface 116 of the cylinder, which would primarily capture
backscattered signals.
[0067] With the singular cylindrical array scanner 110, a first
half of the semi-cylinder elements 16 will be opposed to or facing
the second half of the semi-cylinder elements 16, and thus be
positioned to receive direct transmission signals 30 (see FIG. 3)
at least at varying degrees of angles of incidence. Thus depending
on the amount of defocusing within each transducer, a plurality, or
all, of the non-emitting transducers 16 will be able to receive a
direct transmission signal 30 (FIG. 3) (at varying degrees) from
the emitting transducer 16, leading to a full 3D ultrasound
tomography image of the breast.
[0068] The top end 114 of the cylinder is open, such that the
breast tissue 44 is immersed into the cylindrical array scanner 110
with 2D ultrasound transducer elements 16 surrounding the tissue
44. As with previous embodiments, the ultrasound transducer
elements 16 can be in circular or rectangular shape, and the
surface of the transducer element can be either flat or arc-shaped,
as shown in FIG. 8 and FIG. 9.
[0069] D. Torroidal (Circular) Array Scanner
[0070] FIG. 10 shows a torroidal array scanner 120 having a a
circular array 122 of transducers 16 aligned in a ring that is
configured to encircle the breast 44. A robotic stage 124 may be
provided to allow for translation of the array 122 to and scan the
breast 44 from the chest wall to the nipple region, slice by
slice.
[0071] With the singular torroidal array scanner 120, a first half
of the semi-circle elements 16 will be opposed to or facing the
second half of the semi-circle elements 16, and thus be positioned
to receive direct transmission signals 30 (see FIG. 3) at least at
varying degrees of angles of incidence. Thus, depending on the
amount of defocusing within each transducer, a plurality, or all,
of the non-emitting transducers 16 will be able to receive a direct
transmission signal 30 (at varying degrees) from the emitting
transducer 16.
[0072] The circular array 122 preferably comprises defocused
lens-transducer elements 16b as shown in FIG. 9, enabling 3-D
breast ultrasound tomography. One advantage of the torroidal
configuration 120 is using a fewer number of transducer elements
compared to the cylindrical transducer array 110.
[0073] E. Dual Torroidal (Circular) Array Scanner
[0074] FIG. 11. shows another synthetic-aperture ultrasound breast
tomography scanner 130 that incorporates use of two circular
transducer arrays (upper cirular array 132a and lower circular
array 132b).
[0075] Image resolution depends, at least in part, on ultrasound
illumination of the target medium 44. To increase the ultrasound
out-of-plane illumination angle, an acoustic diverging lens 16b, as
shown in FIG. 9, may be used to widen the elevation beam to the
desired level (e.g. between points B and C in the upper cirular
array 132a and D and E in the lower circular array 132b (conically
diverging beam)). Thus, the defocused ultrasound transducer
elements 16b transmit ultrasound waves propagating not only to the
transducer elements within the same circular array, e.g. between B
and C in the upper ring 132a, but also to the other circular
transducer array, e.g. between D and E in the lower ring 132b. The
upper transducer array 132a may be configured to scan the breast 44
from the chest wall position to the nipple region. At each
position, the lower transducer array 132b may move to different
vertical position in the z-axis to acquire ultrasound data. This
configuration leads to improved vertical resolution of breast
ultrasound tomography images compared that obtained using one
circular transducer array as shown in FIG. 10.
[0076] In practice, the two circular ultrasound transducer arrays
132a and 132b are immersed into the water tank 76 and both encircle
the breast 44. One or both arrays 132a and 132b may be configured
to translate vertically via a motorized stage 134. For example,
during an ultrasound scan, the upper cirular array 132a can be
positioned against the chest wall, while the lower cirular array
132b moves upward from below the nipple region, or vice versa.
[0077] As with previous embodiments, each element of one transducer
array is fired sequentially, and all elements of both transducer
arrays receive ultrasound scattering data 32. The scanner 130
acquires not only ultrasound propagating from one element to all
elements within the same transducer array, but also those
ultrasound waves propagating from the emitting element to all
elements of the other transducer array, leading to a full 3D
ultrasound tomography image of the breast.
[0078] Such a UST system 130 allows recording of volumetric
ultrasound data, and the image resolution limited by slice
thickness will be alleviated. In one exemplary design, the data
acquisition electronics 18 allow a maximum of 768 parallel
channels, so the number of transducers may be halved per array 132a
and 132b. The coarser sampling in the plane of the array will be
compensated by the cross illuminations
[0079] The scanner 130 of FIG. 11 can significantly improve image
resolution and quality compared to those obtained from an
ultrasound tomography system with one circular transducer array. A
3D ultrasound tomography system 10 of this configuration will be
operator independent, which is critical for cancer screening, and
will be more cost-effective than an ultrasound tomography system
with a cylindrical transducer array.
[0080] F. Combination 2D Planar and 2D-Arc Array Scanner
[0081] FIG. 12 shows a scanner 140 comprising a semicircular or
arcuate array 142b having transducers 16 in an opposing or facing
orientation with planar array 142a, with target tissue 44 disposed
between the two. The scanner 140 provides a combination of the
advantages of the cylindrical transducer array 110 with those of
the 2D planner array 100. An ultrasound tomography system 10 with
such combination of transducer arrays improves the range of spatial
coverage for data acquisition, and the planar array 142 can still
be placed near the axillary region.
[0082] G. Combination 1D Beam and Arc Array Scanner
[0083] FIG. 13 illustrates a scanner 150 that reduces the 2D arrays
in FIGS. 12 to 1D arrays (arcuate line array 152b and linear beam
array 152a). This configuration, using a one-dimensional,
straight-phased array 152a and a 1D arc-shaped array, 152 reduces
the number transducers 16, and thus the number of of channels
required for data acquisition electronics 18, while improving the
spatial coverage of data acquisition compared to when using a two
parallel phased transducer array scanner 12 in FIG. 5.
[0084] II. Synthetic Aperture Ultrasound Tomography Methods
[0085] Referring now to FIG. 14, a flow chart of a synthetic
aperture ultrasound tomography method 200 is shown. This method is
preferably used with any of the systems and scanners shown in FIG.
1 through FIG. 14, although other scanning systems are
contemplated. Ideally, the method is used in conjunction with a
scanner that has one or more arrays configured so that a plurality
of transducers 16 of an array, or portion of an array, oppose (at a
spaced-apart distance across the target scanning medium 44) a
plurality of transducers 16 of either another portion of the array,
or a separate array, so that reflection and transmission data may
be acquired with each successive transducer excitation.
[0086] At step 202, the method performs a synthetic aperture
ultrasound scan of the tissue medium in accordance with the
schematic illustration of scanner 12 FIG. 3. At step 204,
reflection and transmission data are simultaneously acquired, as
shown in the method 50 of FIG. 4. At step 206, ultrasound waveform
tomographic imaging is performed on the acquired reflection and
transmission data to generate a high-resolution ultrasound
reconstruction image of the target medium 44.
[0087] As mentioned previously, a particular shortcoming of
existing ultrasound tomographic imaging is that they either use
only transmission data, or reflection data only, for image
reconstructions. In contrast, the synthetic-aperture ultrasound
tomography method 200 of the present invention acquired both
ultrasound transmission and reflection data at the same time, and
use both ultrasound transmission and reflection data for
tomographic reconstructions to greatly improve the shapes and
quantitative values of mechanical properties of abnormalities.
[0088] FIGS. 15 through 18B demonstrate that using numerical
breast-phantom data from ultrasound waveform tomography using both
transmission and reflection data simultaneously significantly
improves the accuracy of tomographic reconstructions, compared to
those obtained using only ultrasound transmission data or only
ultrasound reflection data.
[0089] Numerical phantom data was generated for a
synthetic-aperture ultrasound tomography system with a two parallel
phased transducer array scanner 12 as shown in FIG. 5. Each
transducer array 14a, 15b is comprised of 384 evenly distributed
ultrasound transducer elements, with a pitch size of 0.55 mm. The
two transducer arrays were separated by 20 cm. The ultrasound
source function used is a Ricker wavelet with a central frequency
of 1.0 MHz.
[0090] FIG. 15 shows an image of a numerical breast phantom
containing two different tumors (small, light tumor, and larger
dark tumor). The background sound-speed of the phantom was 1500
m/s, and those of the two tumor speeds were 1530 m/s and 1550 m/s,
respectively. The diameters of the tumors were 2.0 mm and 7.0 mm,
and approximately 1.3 wavelengths and 4.6 wavelengths. The two
tumors were positioned along the longitudinal direction relative to
the ultrasound transducer arrays. A high-order finite-difference
time-domain wave-equation algorithm in accordance with step 206 was
used to compute ultrasound transmission and reflection data.
[0091] FIG. 16A and FIG. 16B show imaging results (tomographic
reconstruction in FIG. 16A, and vertical profile along the center
of the tumors in FIG. 16B) obtained using only the reflection data.
FIG. 17A and FIG. 17B show imaging results (tomographic
reconstruction in FIG. 17A, and vertical profile along the center
of the tumors in FIG. 17B) obtained using only the transmission
data. FIG. 18A and FIG. 18B show imaging results (tomographic
reconstruction in FIG. 18A, and vertical profile along the center
of the tumors in FIG. 18B) obtained using both transmission and
reflection data simultaneously in accordance with method 200.
[0092] The waveform tomographic reconstruction using only the
reflection data (FIG. 16A and FIG. 16B) provides mostly the edge
information of the tumors, and can distinguish the two tumors.
[0093] On the other hand, the waveform tomographic reconstruction
(FIG. 17A and FIG. 17B) using only the transmission data gives
mostly low spatial-wavenumber components of the tumors, and it is
almost impossible to separate the two tumors.
[0094] By contrast, the waveform tomographic reconstruction using
both the transmission and reflection data simultaneously (FIG. 18A
and FIG. 18B) takes the advantages of the above two kinds of
tomographic reconstructions, and produces an image with much
improved tumor edges and sound-speed reconstructions.
[0095] In summary, the synthetic-aperture ultrasound tomography
systems and methods of the present invention acquire ultrasound
transmission and reflection data at the same time, and we have
demonstrated that ultrasound waveform tomography using both
ultrasound transmission and reflection data simultaneously greatly
improves tomographic reconstructions of shapes and sound-speeds of
tumors compared to tomographic reconstructions using only
transmission data or only reflection data.
[0096] Embodiments of the present invention may be described with
reference to flowchart illustrations of methods and systems
according to embodiments of the invention, and/or algorithms,
formulae, or other computational depictions, which may also be
implemented as computer program products. In this regard, each
block or step of a flowchart, and combinations of blocks (and/or
steps) in a flowchart, algorithm, formula, or computational
depiction can be implemented by various means, such as hardware,
firmware, and/or software including one or more computer program
instructions embodied in computer-readable program code logic.
[0097] As will be appreciated, any such computer program
instructions may be loaded onto a computer, including without
limitation a general purpose computer or special purpose computer,
or other programmable processing apparatus to produce a machine,
such that the computer program instructions which execute on the
computer or other programmable processing apparatus create means
for implementing the functions specified in the block(s) of the
flowchart(s).
[0098] Accordingly, blocks of the flowcharts, algorithms, formulae,
or computational depictions support combinations of means for
performing the specified functions, combinations of steps for
performing the specified functions, and computer program
instructions, such as embodied in computer-readable program code
logic means, for performing the specified functions. It will also
be understood that each block of the flowchart illustrations,
algorithms, formulae, or computational depictions and combinations
thereof described herein, can be implemented by special purpose
hardware-based computer systems which perform the specified
functions or steps, or combinations of special purpose hardware and
computer-readable program code logic means.
[0099] Furthermore, these computer program instructions, such as
embodied in computer-readable program code logic, may also be
stored in a computer-readable memory that can direct a computer or
other programmable processing apparatus to function in a particular
manner, such that the instructions stored in the computer-readable
memory produce an article of manufacture including instruction
means which implement the function specified in the block(s) of the
flowchart(s). The computer program instructions may also be loaded
onto a computer or other programmable processing apparatus to cause
a series of operational steps to be performed on the computer or
other programmable processing apparatus to produce a
computer-implemented process such that the instructions which
execute on the computer or other programmable processing apparatus
provide steps for implementing the functions specified in the
block(s) of the flowchart(s), algorithm(s), formula(e), or
computational depiction(s).
[0100] From the discussion above it will be appreciated that the
invention can be embodied in various ways, including the
following:
[0101] 1. A synthetic aperture ultrasound tomography imaging system
for imaging a tissue medium, comprising: one or more ultrasound
transducer arrays; the one or more ultrasound transducer arrays
comprising a plurality of transducers; wherein the plurality of
transducers are configured such that a first set of two or more
transducers are positioned at an opposing spaced-apart orientation
from a second set of two or more transducers such that the first
set of two or more transducers face the second set of two or more
transducers; wherein the first and second sets of two or more
transducers are positioned at spaced-apart locations so as to allow
for the tissue medium to be positioned in between the first and
second sets of two or more transducers; a processor; and
programming executable on said processor and configured for:
exciting a first transducer within the first set of two or more
transducers to generate an ultrasound field within the tissue
medium; and receiving a transmission signal and a reflection signal
from at least the second set of two or more transducers.
[0102] 2. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein the
programming is configured for receiving a reflection signal from
all transducers in the one or more arrays.
[0103] 3. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein the
programming is configured for simultaneously receiving the
reflection and transmission signals from the second set of two or
more transducers.
[0104] 4. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein the
programming is configured for generating an ultrasound waveform
tomography image reconstruction using both the acquired reflection
and transmission signals.
[0105] 5. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein the one or
more ultrasound transducer arrays comprises: a first array of
transducers comprising the first set of two or more transducers;
and a second array of transducers comprising the second set of two
or more transducers; wherein the first array of transducers is
positioned at spaced-apart opposing locations.
[0106] 6. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein both the
first array of transducers and second array of transducers comprise
linear arrays.
[0107] 7. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein at least
one of the first array of transducers and the second array of
transducers comprises a curvilinear array.
[0108] 8. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein the first
array of transducers comprises a linear array and the second array
of transducers comprises a curvilinear array.
[0109] 9. A synthetic aperture ultrasound tomography imaging system
as recited in any of the preceding embodiments, wherein the first
array of transducers comprises a 2-D planar array and the second
array of transducers comprises a 2-D curvilinear array.
[0110] 10. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments: wherein the
one or more ultrasound transducer arrays comprises an arcuate
array; and wherein the first and second sets of two or more
transducers comprise the arcuate array.
[0111] 11. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
arcuate array comprises a first 1-D circular array.
[0112] 12. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
arcuate array comprises a 2-D cylindrical array.
[0113] 13. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, further
comprising a second 1-D circular array positioned concentrically
and at a spaced-apart location with the first 1-D circular
array.
[0114] 14. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments: wherein the
second 1-D circular array comprises a third set of two or more
transducers; and wherein the programming is configured for
receiving a transmission signal and a reflection signal from at
least the third set of two or more transducers.
[0115] 15. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
plurality of transducers comprise an arcuate surface for generating
a diverging ultrasound field within the tissue medium.
[0116] 16. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
one or more arrays of transducers are configured to translate with
respect to the tissue medium.
[0117] 17. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
one or more arrays of transducers are configured to be positioned
in a submersible tank, said tank configured to allow the tissue
medium to hang pendent between the first and second sets of two or
more transducers.
[0118] 18. A synthetic aperture ultrasound tomography imaging
method for imaging a tissue medium with one or more ultrasound
transducer arrays comprising a plurality of transducers,
comprising: exciting a first transducer within the plurality of
transducers to generate an ultrasound field within the tissue
medium; and receiving a transmission signal and a reflection signal
from a second transducer within the one or more ultrasound
transducer arrays.
[0119] 19. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments: wherein the
plurality of transducers are configured such that a first set of
two or more transducers are positioned at an opposing spaced-apart
orientation from a second set of two or more transducers such that
the first set of two or more transducers face the second set of two
or more transducers; wherein the first and second sets of two or
more transducers are positioned at spaced-apart locations so as to
allow for the tissue medium to be positioned in between the first
and second sets of two or more transducers; and wherein the method
further comprises: exciting a first transducer within the first set
of two or more transducers to generate an ultrasound field within
the tissue medium; and receiving a transmission signal and a
reflection signal from at least the second set of two or more
transducers.
[0120] 20. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, further
comprising receiving a reflection signal from all transducers in
the one or more arrays.
[0121] 21. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, further
comprising simultaneously receiving the reflection and transmission
signals from the second set of two or more transducers.
[0122] 22. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, further
comprising generating an ultrasound waveform tomography image
reconstruction using both the acquired reflection and transmission
signals.
[0123] 23. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
one or more ultrasound transducer arrays comprises: a first array
of transducers comprising the first set of two or more transducers;
and a second array of transducers comprising the second set of two
or more transducers; wherein the first array of transducers is
positioned at spaced-apart opposing locations.
[0124] 24. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein both
the first array of transducers and second array of transducers
comprise linear arrays.
[0125] 25. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein at
least one of the first array of transducers and the second array of
transducers comprises a curvilinear array.
[0126] 26. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
first array of transducers comprises a linear array and the second
array of transducers comprises a curvilinear array.
[0127] 27. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
first array of transducers comprises a 2-D planar array and second
array of transducers comprises a 2-D curvilinear array.
[0128] 28. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments: wherein the
one or more ultrasound transducer arrays comprises an arcuate
array; and wherein the first and second sets of two or more
transducers comprise the arcuate array.
[0129] 29. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
arcuate array comprises a first 1-D circular array.
[0130] 30. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
arcuate array comprises a 2-D cylindrical array.
[0131] 31. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein a
second 1-D circular array is positioned concentrically and at a
spaced-apart location with the first 1-D circular array.
[0132] 32. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments: wherein the
second 1-D circular array comprises a third set of two or more
transducers; and wherein the method further comprises receiving a
transmission signal and a reflection signal from at least the third
set of two or more transducers.
[0133] 33. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
plurality of transducers comprise an arcuate surface for generating
a diverging ultrasound field within the tissue medium.
[0134] 34. A synthetic aperture ultrasound tomography imaging
method as recited in any of the preceding embodiments, wherein the
one or more arrays of transducers are configured to translate with
respect to the tissue medium.
[0135] 35. A synthetic aperture ultrasound tomography imaging
system for imaging a tissue medium with one or more ultrasound
transducer arrays comprising a plurality of transducers,
comprising: a processor; and programming executable on said
processor and configured for: exciting a first transducer within
the first set of two or more transducers to generate an ultrasound
field within the tissue medium; and receiving a transmission signal
and a reflection signal from at least the second set of two or more
transducers.
[0136] 36. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments: wherein the
plurality of transducers are configured such that a first set of
two or more transducers are positioned at an opposing spaced-apart
orientation from a second set of two or more transducers such that
the first set of two or more transducers face the second set of two
or more transducers; and wherein the first and second sets of two
or more transducers are positioned at spaced-apart locations so as
to allow for the tissue medium to be positioned in between the
first and second sets of two or more transducers; and wherein the
programming is configured for: exciting a first transducer within
the first set of two or more transducers to generate an ultrasound
field within the tissue medium; and receiving a transmission signal
and a reflection signal from at least the second set of two or more
transducers.
[0137] 37. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
programming is configured for receiving a reflection signal from
all transducers in the one or more arrays.
[0138] 38. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
programming is configured for simultaneously receiving the
reflection and transmission signals from the second set of two or
more transducers.
[0139] 39. A synthetic aperture ultrasound tomography imaging
system as recited in any of the preceding embodiments, wherein the
programming is configured for generating an ultrasound waveform
tomography image reconstruction using both the acquired reflection
and transmission signals.
[0140] Although the description herein contains many details, these
should not be construed as limiting the scope of the disclosure but
as merely providing illustrations of some of the presently
preferred embodiments. Therefore, it will be appreciated that the
scope of the disclosure fully encompasses other embodiments which
may become obvious to those skilled in the art.
[0141] In the claims, reference to an element in the singular is
not intended to mean "one and only one" unless explicitly so
stated, but rather "one or more." All structural, chemical, and
functional equivalents to the elements of the disclosed embodiments
that are known to those of ordinary skill in the art are expressly
incorporated herein by reference and are intended to be encompassed
by the present claims. Furthermore, no element, component, or
method step in the present disclosure is intended to be dedicated
to the public regardless of whether the element, component, or
method step is explicitly recited in the claims. No claim element
herein is to be construed as a "means plus function" element unless
the element is expressly recited using the phrase "means for". No
claim element herein is to be construed as a "step plus function"
element unless the element is expressly recited using the phrase
"step for".
* * * * *