Systems and methods for plane wave compounding in ultrasound imaging
Systems and methods for Plane Wave Compounding (“PWC”) are provided for improving image quality with reduced phase shift errors. The initial phase difference (“IPD”) between two PW transmissions is related to the phase shift error. When the absolute value of IPD is larger than π/2, the phase shift error occurs. An Initial-Phase-Compensated PWC (“IPCPWC”) method may be used to compensate the initial phase of echo signals from each PW transmit and maintain the absolute value of IPD smaller than π/2. IPCPWC methods may also include increased motion signal-to-noise ratio and reduced jitter.
1. A method for ultrasound plane wave compounding imaging, comprising:
a) accessing ultrasound plane wave time series data with a computer system, wherein the ultrasound plane wave time series data were acquired from a region of a subject and comprise ultrasound plane wave data acquired for a plurality of different transmission angles at each of a plurality of time points;
b) selecting a first data set from the ultrasound plane wave time series data corresponding to ultrasound plane wave data acquired for the plurality of the different transmission angles at a first time point;
c) selecting a second data set from the ultrasound plane wave time series data corresponding to ultrasound plane wave data acquired for the plurality of the different transmission angles at a second time point that is subsequent to the first time point;
d) calculating with the computer system for each of the plurality of different transmission angles, an initial phase angle mean value between ultrasound plane wave data in the first data set and the second data set corresponding to a common one of the plurality of the different transmission angles;
e) generating initial-phase-compensated plane wave data by adjusting the ultrasound plane wave data in the first data set and the second data set using the initial phase angle mean values calculated for each of the plurality of different transmission angles;
f) constructing phase-compensated images from the initial-phase-compensated plane wave data, wherein the phase-compensated images depict the region of the subject at the first time point and the second time point.
2. The method of claim 1 , wherein adjusting the ultrasound plane wave data in the first data set and the second data set includes subtracting the initial phase angle mean value calculated for a given transmission angle from a phase value of the ultrasound plane wave data in the first data set and the second data set corresponding to the given transmission angle.
3. The method of claim 1 , further comprising repeating steps b)-f) for successive pairs of time points in the plurality of time points, thereby constructing a time series of phase-compensated images.
4. The method of claim 1 , wherein constructing phase-compensated images from the initial-phase-compensated plane wave data includes coherently combining initial-phase-compensated ultrasound plane wave data in the first data set to generate a phase-compensated image depicting the region of the subject at the first time point, and coherently combining initial-phase-compensated ultrasound plane wave data in the second data set to generate a phase-compensated image depicting the region of the subject at the second time point.
5. The method of claim 1 , wherein the ultrasound plane wave data in the ultrasound plane wave time series data comprise one of in-phase quadrature (IQ) data or radio frequency (RF) signal data.
6. The method of claim 1 , wherein accessing the ultrasound plane wave time series data with the computer system comprises:
operating the computer system to control an ultrasound system to generate a series of angled wave emissions corresponding to the plurality of different transmission angles over a duration of time corresponding to the plurality of time points; and
controlling the ultrasound system with the computer system to acquire the ultrasound plane wave data in response thereto.
7. The method of claim 1 , wherein one or more shear waves were induced in the region of the subject prior to acquiring the ultrasound plane wave data such that the ultrasound plane wave times series data are indicative of shear wave motion occurring in the region of the subject.
8. The method of claim 7 , further comprising estimating motion data from the phase-compensated images, wherein the motion data are indicative of the shear wave motion of the one or more shear waves in the region of the subject.
9. The method of claim 8 , wherein the motion data are estimated from a phase shift between the first time point and the second time point, wherein the phase shift comprises:
δθ
=
ang
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×
R
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)
=
ang
(
1
N
2
(
∑
n
=
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A
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m
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n
2
A
n
A
m
)
e
i
ω
c
δ
t
)
=
ω
c
δ
t
.
wherein δθ represents the phase shift, m and n are different ones of the plurality of transmission angles, t is time along a depth dimension, A n is an amplitude of a signal in the ultrasound plane wave data, ω c is a center frequency of a carrier signal, and δt represents time delay.
10. The method of claim 8 , wherein the motion data are estimated from a phase shift between the first time point and the second time point, wherein the phase shift comprises
δ
θ
=
ang
(
S
¯
×
R
¯
*
)
=
ω
c
δ
t
wherein δθ represents the phase shift, t is time along a depth dimension, ω c is a center frequency of a carrier signal, and δt is a time delay.
11. A system for ultrasound plane wave compounding imaging, comprising:
an ultrasound imaging system configured to acquire plane wave time series data for plane wave compounding imaging;
a computer system in communication with the ultrasound imaging system and configured to:
i) access ultrasound plane wave time series data acquired with the ultrasound imaging system, wherein the ultrasound plane wave time series data were acquired from a region of a subject and comprise ultrasound plane wave data acquired for a plurality of different transmission angles at each of a plurality of time points;
ii) select a first data set from the ultrasound plane wave time series data corresponding to ultrasound plane wave data acquired for the plurality of the different transmission angles at a first time point;
iii) select a second data set from the ultrasound plane wave time series data corresponding to ultrasound plane wave data acquired for the plurality of the different transmission angles at a second time point that is subsequent to the first time point;
iv) calculate for each of the plurality of different transmission angles an initial phase angle mean value between ultrasound plane wave data in the first data set and the second data set corresponding to a common one of the plurality of the different transmission angles;
v) generate initial-phase-compensated plane wave data by adjusting the ultrasound plane wave data in the first data set and the second data set using the initial phase angle mean values calculated for each of the plurality of different transmission angles;
vi) construct phase-compensated images from the initial-phase-compensated plane wave data, wherein the phase-compensated images depict the region of the subject at the first time point and the second time point.
12. The system of claim 11 , wherein the computer system is further configured to adjust the ultrasound plane wave data in the first data set and the second data set by subtracting the initial phase angle mean value calculated for a given transmission angle from a phase value of the ultrasound plane wave data in the first data set and the second data set corresponding to the given transmission angle.
13. The system of claim 11 , wherein the computer system is further configured to repeat steps ii)-vi) for successive pairs of time points in the plurality of time points, thereby constructing a time series of phase-compensated images.
14. The system of claim 11 , wherein the computer system is further configured to construct the phase-compensated images from the initial-phase-compensated plane wave data by coherently combining initial-phase-compensated ultrasound plane wave data in the first data set to generate a phase-compensated image depicting the region of the subject at the first time point, and coherently combining initial-phase-compensated ultrasound plane wave data in the second data set to generate a phase-compensated image depicting the region of the subject at the second time point.
15. The system of claim 11 , wherein the ultrasound plane wave data in the ultrasound plane wave time series data comprise one of in-phase quadrature (IQ) data or radio frequency (RF) signal data.
16. The system of claim 11 , wherein the computer system is further configured to access the ultrasound plane wave time series data by being configured to:
control the ultrasound system to generate a series of angled wave emissions corresponding to the plurality of different transmission angles over a duration of time corresponding to the plurality of time points; and
control the ultrasound system to acquire the ultrasound plane wave data in response thereto.
17. The system of claim 11 , wherein one or more shear waves were induced in the region of the subject prior to acquiring the ultrasound plane wave data such that the ultrasound plane wave times series data are indicative of shear wave motion occurring in the region of the subject.
18. The system of claim 17 , wherein the computer system is further configured to estimate motion data from the phase-compensated images, wherein the motion data are indicative of the shear wave motion of the one or more shear waves in the region of the subject.
19. The system of claim 18 , wherein the computer system is further configured to estimate motion data from a phase shift between the first time point and the second time point, wherein the phase shift comprises:
δθ
=
ang
(
S
¯
×
R
¯
*
)
=
ang
(
1
N
2
(
∑
n
=
1
N
A
n
A
n
+
∑
m
>
n
2
A
n
A
m
)
e
i
ω
c
δ
t
)
=
ω
c
δ
t
.
wherein δθ is the phase shift, m and n are different ones of the plurality of transmission angles, t is time along a depth dimension, A n is an amplitude of a signal in the ultrasound plane wave data, ω c is a center frequency of a carrier signal, and δt is a time delay.
20. The system of claim 18 , wherein the computer system is further configured to estimate motion data from a phase shift between the first time point and the second time point, wherein the phase shift comprises:
δ
θ
=
ang
(
S
¯
×
R
¯
*
)
=
ω
c
δ
t
wherein δθ represents the phase shift, t is time along a depth dimension, ω c is a center frequency of a carrier signal, and δt is a time delay.