Patent US6423057B1 successfully refreshed from Google Patents.
Patent US6200266B1 successfully refreshed from Google Patents.
US6200266B1
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US
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Method and apparatus for ultrasound imaging using acoustic impedance reconstruction
Assignee: MEDSONICS US Inc
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Filing: 1999-03-31
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Granted: 2001-03-13
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Expires: 2019-03-31
Abstract
Abstract An ultrasound imaging system employs acoustic impedance reconstruction to produce high-resolution images of anatomical structures, which are virtually free of speckle. Determination of the acoustic impedance profile involves prefiltering of the incident ultrasound signal and the ultrasound signal reflected from the specimen to be imaged. A time domain window function is applied to both the incident and reflected signals, and an N-point FFT is computed for both the digitized incident and reflected signals to obtain the incident and reflected spectrums. A complex division of the reflected spectrum by the incident spectrum is performed to obtain the transfer function. A window function having a sharp, low-frequency cutoff is applied to the transfer function prior to performing an inverse FFT to obtain the estimated impulse response. The acoustic impedance of individual A-scans is calculated from the impulse response using the plane wave Born approximation, involving integration and exponentiation of the estimated impulse response. By mechanically or electronically scanning the transducer along a line, a series of A-scan acoustic impedance profiles are calculated and used to produce a two-dimensional, grey-scale B-scan image.
Inventors
- 👤 Nima Shokrollahi
- 👤 William Tobocman
- 👤 Sanford Roth
- 👤 Joseph Izatt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 23:48
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/52; G01S7/52017; G01S7/52053; G01S7/52057; G01S7/5206; G01S7/52061; G01S15/00; G01S15/88; G01S15/89; G01S15/8906; G01S15/8993; G01S7/52023; G01S7/52036; G01S7/52046; A; A61; A61B; A61B8/00; A61B8/08; A61B8/0858; A61B8/13; G01S7/52068; G01S7/52069
Claims Analysis
Total Claims: 45
Claim 1
Independent Claim
158 words
An ultrasound imaging system, comprising: a transducer adapted to emit an incident ultrasonic signal toward a specimen, said transducer receiving a reflection of the incident ultrasonic signal from the specimen and generating an electrical signal which represents a reflected ultrasonic signal; a signal processor which reconstructs an acoustic impedance of a portion of the specimen through which the reflected ultrasonic signal passes by: computing a Fourier transform of the electrical signal which represents the reflected ultrasonic signal to obtain a reflected signal spectrum; dividing the reflected signal spectrum by a spectrum of the incident ultrasonic signal to obtain a transfer function; applying a frequency-domain window function having a sharp, low-frequency cutoff to the transfer function; computing an inverse Fourier transform of the windowed transfer function to obtain an impulse response; and calculating the acoustic impedance from the impulse response; and an imaging device adapted to form an image of the specimen in accordance with the reconstructed acoustic impedance.
Claim 2
Dependent Claim
158 words
An ultrasound imaging system, comprising: a transducer adapted to emit an incident ultrasonic signal toward a specimen, said transducer receiving a reflection of the incident ultrasonic signal from the specimen and generating an electrical signal which represents a reflected ultrasonic signal; a signal processor which reconstructs an acoustic impedance of a portion of the specimen through which the reflected ultrasonic signal passes by: computing a Fourier transform of the electrical signal which represents the reflected ultrasonic signal to obtain a reflected signal spectrum; dividing the reflected signal spectrum by a spectrum of the incident ultrasonic signal to obtain a transfer function; applying a frequency-domain window function having a sharp, low-frequency cutoff to the transfer function; computing an inverse Fourier transform of the windowed transfer function to obtain an impulse response; and calculating the acoustic impedance from the impulse response; and an imaging device adapted to form an image of the specimen in accordance with the reconstructed acoustic impedance.
Claim 3
Dependent Claim
30 words
The system according to claim 1 , wherein said signal processor calculates the acoustic impedance by integrating and exponentiating the impulse response in accordance with a plane wave Born approximation.
Claim 4
Dependent Claim
24 words
The system according to claim 1 , wherein said window function reduces to zero a magnitude of a DC component of the transfer function.
Claim 5
Dependent Claim
52 words
The system according to claim 3 , wherein the magnitude of at least one of a lowest frequency component above the DC component of the transfer function, a second lowest frequency component of the transfer function and a third lowest frequency component of the transfer function is unattenuated by the window function.
Claim 6
Dependent Claim
25 words
The system according to claim 4 , wherein a magnitude of the lowest frequency component of the transfer function is unattenuated by the window function.
Claim 7
Dependent Claim
31 words
The system according to claim 1 , wherein the window function is a rectangular filter having a sharp, high-frequency cutoff corresponding to a high-frequency end of a bandwidth of said transducer.
Claim 8
Dependent Claim
36 words
The system according to claim 1 , wherein the window function smoothly approaches zero at a high-frequency end, such that magnitudes of high-frequency components of the transfer function are gradually attenuated to zero with increasing frequency.
Claim 9
Dependent Claim
30 words
The system according to claim 1 , wherein said signal processor applies a time domain pre-window to the electrical signal prior to computing the Fourier transform of the electrical signal.
Claim 10
Dependent Claim
16 words
The system according to claim 8 , wherein the time domain pre-window is a Hamming window.
Claim 11
Dependent Claim
49 words
The system according to claim 1 , further comprising a scan controller configured to control said transducer to emit a sequence of incident ultrasonic signals which respectively travel along adjacent lines within the specimen, said signal processor reconstructing an acoustic impedance corresponding to each of the incident ultrasonic signals.
Claim 12
Dependent Claim
41 words
The system according to claim 10 , wherein said transducer is a phased-array of transducer elements, wherein a direction of each of the incident ultrasonic signals is controlled by a relative phase of individual ultrasonic signals emitted by the transducer elements.
Claim 13
Dependent Claim
33 words
The system according to claim 11 , wherein said transducer is controllable by said scan controller to scan in at least one of the following scanning formats: linear; steered linear, sector, and circular.
Claim 14
Dependent Claim
28 words
The system according to claim 10 , further comprising a movable platform on which said transducer is mounted, said scan controller effecting scanning by displacing said movable platform.
Claim 15
Dependent Claim
33 words
The system according to claim 10 , wherein said scan controller controls said transducer to scan in a plane of the specimen, said imaging device forming a two-dimensional B-scan image of the specimen.
Claim 16
Dependent Claim
18 words
The system according to claim 1 , wherein said imaging device produces a three-dimensional image of the specimen.
Claim 17
Dependent Claim
18 words
The system according to claim 1 , wherein said signal processor reconstructs the acoustic impedance in real time.
Claim 18
Dependent Claim
20 words
The system according to claim 16 , wherein said imaging device updates the image of the specimen in real time.
Claim 19
Dependent Claim
46 words
The system according to claim 1 , wherein the incident ultrasonic signal emitted by said transducer has a center frequency in the range between 3 and 5 MHz, inclusive, the incident ultrasonic signal imaging a field of view in a depth dimension of approximately 8 mm.
Claim 20
Dependent Claim
21 words
The system according to claim 1 , wherein said imaging device includes at least one of a display and a printer.
Claim 21
Dependent Claim
26 words
The system according to claim 1 , further comprising: a memory adapted to store image information derived from the acoustic impedance reconstructed by said signal processor.
Claim 22
Dependent Claim
33 words
The system according to claim 1 , further comprising: a transmitter for transmitting image information to a remote location over at least one of: a fiber optic medium, a wire and free space.
Claim 23
Independent Claim
139 words
A method of generating an ultrasound image, comprising the steps of: a) emitting an incident ultrasonic signal toward a specimen; b) receiving a reflection of the incident ultrasonic signal from the specimen and generating an electrical signal which represents a reflected ultrasonic signal; c) computing a Fourier transform of the electrical signal which represents the reflected ultrasonic signal to obtain a reflected signal spectrum; d) dividing the reflected signal spectrum by a spectrum of the incident ultrasonic signal to obtain a transfer function; e) applying a frequency-domain window function having a sharp, low-frequency cutoff to the transfer function; f) computing an inverse Fourier transform of the windowed transfer function to obtain an impulse response; g) calculating an acoustic impedance profile from the impulse response; and h) forming an image of the specimen in accordance with the acoustic impedance profile.
Claim 24
Independent Claim
139 words
A method of generating an ultrasound image, comprising the steps of: a) emitting an incident ultrasonic signal toward a specimen; b) receiving a reflection of the incident ultrasonic signal from the specimen and generating an electrical signal which represents a reflected ultrasonic signal; c) computing a Fourier transform of the electrical signal which represents the reflected ultrasonic signal to obtain a reflected signal spectrum; d) dividing the reflected signal spectrum by a spectrum of the incident ultrasonic signal to obtain a transfer function; e) applying a frequency-domain window function having a sharp, low-frequency cutoff to the transfer function; f) computing an inverse Fourier transform of the windowed transfer function to obtain an impulse response; g) calculating an acoustic impedance profile from the impulse response; and h) forming an image of the specimen in accordance with the acoustic impedance profile.
Claim 25
Dependent Claim
30 words
The method according to claim 22 , wherein step f) includes integrating and exponentiating the impulse response in accordance with a plane wave Born approximation to obtain the acoustic impedance.
Claim 26
Dependent Claim
24 words
The method according to claim 22 , wherein step e) includes reducing to zero a magnitude of a DC component of the transfer function.
Claim 27
Dependent Claim
51 words
The method according to claim 24 , wherein step e) includes not attenuating a magnitude of at least one of: a lowest frequency component above the DC component of the transfer function, a second lowest frequency component of the transfer function and a third lowest frequency component of the transfer function.
Claim 28
Dependent Claim
24 words
The method according to claim 25 , wherein step e) includes not attenuating a magnitude of the lowest frequency component of the transfer function.
Claim 29
Dependent Claim
34 words
The method according to claim 22 , wherein the window function applied in step e) is a rectangular filter having a sharp, high-frequency cutoff corresponding to a high-frequency end of the incident ultrasonic signal.
Claim 30
Dependent Claim
40 words
The method according to claim 22 , wherein the window function applied in step e) smoothly approaches zero at a high-frequency end, such that magnitudes of high-frequency components of the transfer function are gradually attenuated to zero with increasing frequency.
Claim 31
Dependent Claim
34 words
The method according to claim 22 , further comprising the step of: i) applying a time domain pre-filter to the reflected electrical signal prior to computing the Fourier transform of the reflected electrical signal.
Claim 32
Dependent Claim
51 words
The method according to claim 22 , further comprising the step of: i) effecting a scan by repeating steps a) through g) along a plurality of different, adjacent paths within the specimen, wherein step h) includes forming an image using the acoustic impedance calculated for each of the plurality of paths.
Claim 33
Dependent Claim
29 words
The method according to claim 30 , wherein step i) includes controlling a direction of the incident ultrasonic signal by setting relative phases of a phased-array of transducer elements.
Claim 34
Dependent Claim
27 words
The method according to claim 31 , wherein step i) includes scanning in at least one of the following scanning formats: linear; steered linear, sector, and circular.
Claim 35
Dependent Claim
18 words
The method according to claim 30 , wherein step i) includes mechanically displacing a transducer to effect scanning.
Claim 36
Dependent Claim
31 words
The method according to claim 30 , wherein the plurality of paths form a plane in the specimen, and wherein step h) includes forming a two-dimensional B-scan image of the specimen.
Claim 37
Dependent Claim
18 words
The method according to claim 22 , wherein step h) includes forming a three-dimensional image of the specimen.
Claim 38
Dependent Claim
17 words
The method according to claim 22 , wherein steps c) through h) are performed in real time.
Claim 39
Dependent Claim
29 words
The method according to claim 22 , wherein step a) includes emitting the incident ultrasonic signal having a center frequency in the range between 3 and 5 MHz, inclusive.
Claim 40
Dependent Claim
110 words
The method according to claim 22 , further comprising the steps of: i) prior to step h), determining whether the acoustic impedance profile meets a predetermined requirement; j) when the acoustic impedance profile fails to meet the predetermined requirement, constraining values of certain components of the acoustic impedance profile; k) computing amplitudes of low frequency components of the transfer function below the sharp, low-frequency cutoff from the constrained values of the certain components of the acoustic impedance profile; l) repeating steps f), g), i), j) and k) at most L times, where L is a positive integer, or until the acoustic impedance profile meets the predetermined requirement in step i).
Claim 41
Dependent Claim
95 words
The method according to claim 38 , wherein: the predetermined requirements is that the value of all of the components of the acoustic impedance profile be at least 1.0; and step j) includes: dividing the acoustic impedance profile into N regions, where N is an integer greater than 1; for each region, identifying a component of the acoustic impedance profile having a minimum value within the region; for each region, if the minimum value is less than 1.0, constraining the value of the identified component in the region to a value no less than 1.0.
Claim 42
Dependent Claim
33 words
The method according to claim 22 , further comprising the step of: i) prior to step f), adjusting amplitudes of components of the transfer function to compensate for attenuation caused by intervening tissue.
Claim 43
Dependent Claim
254 words
An ultrasound imaging system, comprising: a transducer adapted to emit an incident ultrasonic signal toward a specimen, said transducer receiving a reflection of the incident ultrasonic signal from the specimen and generating an electrical signal which represents a reflected ultrasonic signal; a signal processor which reconstructs an acoustic impedance of a portion of the specimen through which the reflected ultrasonic signal passes by: a) computing a Fourier transform of the electrical signal which represents the reflected ultrasonic signal to obtain a reflected signal spectrum; b) dividing the reflected signal spectrum by a spectrum of the incident ultrasonic signal to obtain a transfer function; c) applying a frequency-domain window function having a sharp, low-frequency cutoff to the transfer function; d) computing an inverse Fourier transform of the windowed transfer function to obtain an impulse response; e) calculating an acoustic impedance profile from the impulse response; f) determining whether the acoustic impedance profile meets a predetermined requirement; g) when the acoustic impedance profile fails to meet the predetermined requirement, constraining values of certain components of the acoustic impedance profile; h) computing amplitudes of low-frequency components of the transfer function below the sharp, low-frequency cutoff from the constrained values of the certain components of the acoustic impedance profile; and i) repeating steps d) through h) at most L times, where L is a positive integer, or until the acoustic impedance profile meets the predetermined requirement in step f); and an imaging device adapted to form an image of the specimen in accordance with the acoustic impedance profile.
Claim 44
Dependent Claim
254 words
An ultrasound imaging system, comprising: a transducer adapted to emit an incident ultrasonic signal toward a specimen, said transducer receiving a reflection of the incident ultrasonic signal from the specimen and generating an electrical signal which represents a reflected ultrasonic signal; a signal processor which reconstructs an acoustic impedance of a portion of the specimen through which the reflected ultrasonic signal passes by: a) computing a Fourier transform of the electrical signal which represents the reflected ultrasonic signal to obtain a reflected signal spectrum; b) dividing the reflected signal spectrum by a spectrum of the incident ultrasonic signal to obtain a transfer function; c) applying a frequency-domain window function having a sharp, low-frequency cutoff to the transfer function; d) computing an inverse Fourier transform of the windowed transfer function to obtain an impulse response; e) calculating an acoustic impedance profile from the impulse response; f) determining whether the acoustic impedance profile meets a predetermined requirement; g) when the acoustic impedance profile fails to meet the predetermined requirement, constraining values of certain components of the acoustic impedance profile; h) computing amplitudes of low-frequency components of the transfer function below the sharp, low-frequency cutoff from the constrained values of the certain components of the acoustic impedance profile; and i) repeating steps d) through h) at most L times, where L is a positive integer, or until the acoustic impedance profile meets the predetermined requirement in step f); and an imaging device adapted to form an image of the specimen in accordance with the acoustic impedance profile.
Claim 45
Dependent Claim
97 words
The apparatus according to claim 41 , wherein: the predetermined requirements include the requirement that the value of all of the components of the acoustic impedance profile be at least 1.0; and step g) includes: dividing the acoustic impedance profile into N regions, where N is an integer greater than 1; for each region, identifying a component of the acoustic impedance profile having a minimum value within the region; for each region, if the minimum value is less than 1.0, constraining the value of the identified component in the region to a value no less than 1.0.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-03-12 | 2004-09-11 | 2005-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-03-12 | 2008-09-11 | 2009-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-03-12 | 2012-09-11 | 2013-03-13 | $7700.00 | Window Closed / Lapsed |