阅读说明：本技术 使用基波和谐波信号的定量超声 (Quantitative ultrasound using fundamental and harmonic signals ) 是由 Y·拉拜德 于 2020-02-06 设计创作，主要内容包括：一种系统和方法,包括：存储基波频带的参考体模的回波信号功率谱和谐波频带的参考体模的回波信号功率谱；获取基波频带的组织区域的回波信号功率谱和谐波频带的组织区域的回波信号功率谱；基于基波频带的组织区域的回波信号功率谱和基波频带的参考体模的回波信号功率谱来确定第一反向散射系数；基于谐波频带的组织区域的回波信号功率谱和谐波频带的参考体模的回波信号功率谱来确定第二反向散射系数；以及基于第一反向散射系数和第二反向散射系数来确定组织区域的非线性度。(A system and method comprising: storing the echo signal power spectrum of the reference phantom of the fundamental frequency band and the echo signal power spectrum of the reference phantom of the harmonic frequency band; acquiring an echo signal power spectrum of a tissue region of a fundamental wave frequency band and an echo signal power spectrum of a tissue region of a harmonic wave frequency band; determining a first backscatter coefficient based on an echo signal power spectrum of the tissue region of the fundamental frequency band and an echo signal power spectrum of a reference phantom of the fundamental frequency band; determining a second backscatter coefficient based on the echo signal power spectrum of the tissue region of the harmonic band and the echo signal power spectrum of the reference phantom of the harmonic band; and determining a non-linearity of the tissue region based on the first backscatter coefficient and the second backscatter coefficient.)

1. An ultrasound system, comprising:

a memory storing an echo signal power spectrum of a reference phantom for a fundamental frequency band and an echo signal power spectrum of a reference phantom for a harmonic frequency band; and

a processing unit to:

controlling the ultrasonic system to acquire an echo signal power spectrum of a tissue region of a fundamental frequency band and an echo signal power spectrum of a tissue region of a harmonic frequency band;

determining a first backscatter coefficient based on an echo signal power spectrum of the tissue region of the fundamental frequency band and an echo signal power spectrum of a reference phantom of the fundamental frequency band;

determining a second backscatter coefficient based on the echo signal power spectrum of the tissue region of the harmonic band and the echo signal power spectrum of the reference phantom of the harmonic band; and

the non-linearity of the tissue region is determined based on the first backscatter coefficient and the second backscatter coefficient.

2. The ultrasound system of claim 1, wherein a substantially similar scan setup is used to acquire the echo signal power spectrum of the reference phantom for the fundamental frequency band and the echo signal power spectrum of the tissue region for the fundamental frequency band.

3. The ultrasound system of claim 2, wherein a substantially similar scan setup is used to acquire an echo signal power spectrum of a reference phantom of a harmonic band and an echo signal power spectrum of a tissue region of the harmonic band.

4. The system of claim 1, the memory to store an echo signal power spectrum of the second reference phantom for a fundamental frequency band and an echo signal power spectrum of the second reference phantom for a harmonic frequency band, an

The processing unit further determines an echo signal power spectrum of the reference phantom using the fundamental frequency band for determining the first backscatter coefficient and an echo signal power spectrum of the reference phantom using the harmonic frequency band for determining the second backscatter coefficient based on a correlation between the tissue region and the reference phantom.

5. The system of claim 4, having acquired an echo signal power spectrum of a reference phantom in a fundamental frequency band and an echo signal power spectrum of a reference phantom in a harmonic frequency band using a first scan setting,

the memory stores a second echo signal power spectrum of the reference phantom for the fundamental frequency band and a second echo signal power spectrum of the reference phantom for the harmonic frequency band, the second echo signal power spectrum acquired using a second scan setting,

obtaining an echo signal power spectrum of a tissue region of a fundamental frequency band and an echo signal power spectrum of a tissue region of a harmonic frequency band using a third scan setting, an

Wherein the processing unit is for determining an echo signal power spectrum of the reference phantom using the fundamental frequency band and an echo signal power spectrum of the reference phantom using the harmonic frequency band based on a correlation between the first scan setting and the third scan setting for determining the first backscatter coefficient and determining the second backscatter coefficient.

6. The system of claim 1, the processing unit to further:

the attenuation coefficient of the tissue region is determined based on the echo signal power spectrum of the tissue region of the harmonic band, the echo signal power spectrum of the reference phantom of the harmonic band, and the attenuation coefficient of the reference phantom.

7. The system of claim 6, further comprising:

a display for simultaneously displaying the second backscatter coefficient, the attenuation coefficient of the tissue region, the non-linearity, and a B-mode image of the tissue region.

8. A method, comprising:

storing the echo signal power spectrum of the reference phantom of the fundamental frequency band and the echo signal power spectrum of the reference phantom of the harmonic frequency band in the ultrasonic system;

controlling the ultrasonic system to acquire an echo signal power spectrum of a tissue region of a fundamental frequency band and an echo signal power spectrum of a tissue region of a harmonic frequency band;

determining a first backscatter coefficient based on an echo signal power spectrum of the tissue region of the fundamental frequency band and an echo signal power spectrum of a reference phantom of the fundamental frequency band;

determining a second backscatter coefficient based on the echo signal power spectrum of the tissue region of the harmonic band and the echo signal power spectrum of the reference phantom of the harmonic band; and

the non-linearity of the tissue region is determined based on the first backscatter coefficient and the second backscatter coefficient.

9. The method of claim 8, wherein the echo signal power spectrum of the reference phantom of the fundamental frequency band and the echo signal power spectrum of the tissue region of the fundamental frequency band are acquired using substantially similar scan settings.

10. The method of claim 9, wherein the echo signal power spectrum of the reference phantom of the harmonic band and the echo signal power spectrum of the tissue region of the harmonic band are acquired using substantially similar scan settings.

11. The method of claim 8, further comprising:

storing the echo signal power spectrum of the second reference phantom for the fundamental frequency band and the echo signal power spectrum of the second reference phantom for the harmonic frequency band, an

The echo signal power spectrum of the reference phantom using the fundamental frequency band is determined for determining the first backscatter coefficient based on the correlation between the tissue region and the reference phantom, and the echo signal power spectrum of the reference phantom using the harmonic frequency band is determined for determining the second backscatter coefficient.

12. The method of claim 11, having acquired an echo signal power spectrum of a reference phantom in a fundamental frequency band and an echo signal power spectrum of a reference phantom in a harmonic frequency band using a first scan setting, further comprising:

storing in the ultrasound system a second echo signal power spectrum of the reference phantom for the fundamental frequency band and a second echo signal power spectrum of the reference phantom for the harmonic frequency band, the second echo signal power spectrum being acquired using a second scan setting,

wherein the echo signal power spectrum of the tissue region of the fundamental frequency band and the echo signal power spectrum of the tissue region of the harmonic frequency band are acquired using a third scan setting, an

Further comprising: the echo signal power spectrum of the reference phantom using the fundamental frequency band is determined for determining the first backscatter coefficient based on a correlation between the first scan setting and the third scan setting, and the echo signal power spectrum of the reference phantom using the harmonic frequency band is determined for determining the second backscatter coefficient.

13. The method of claim 8, further comprising:

the attenuation coefficient of the tissue region is determined based on the echo signal power spectrum of the tissue region of the harmonic band, the echo signal power spectrum of the reference phantom of the harmonic band, and the attenuation coefficient of the reference phantom.

14. The method of claim 13, further comprising:

the second backscatter coefficient, the attenuation coefficient of the tissue region, the non-linearity, and a B-mode image of the tissue region are displayed simultaneously.

15. An ultrasound imaging system for:

storing the echo signal power spectrum of the reference phantom of the fundamental frequency band and the echo signal power spectrum of the reference phantom of the harmonic frequency band;

acquiring an echo signal power spectrum of a tissue region of a fundamental wave frequency band and an echo signal power spectrum of a tissue region of a harmonic wave frequency band;

determining a first backscatter coefficient based on an echo signal power spectrum of the tissue region of the fundamental frequency band and an echo signal power spectrum of a reference phantom of the fundamental frequency band;

determining a second backscatter coefficient based on the echo signal power spectrum of the tissue region of the harmonic band and the echo signal power spectrum of the reference phantom of the harmonic band; and

the non-linearity of the tissue region is determined based on the first backscatter coefficient and the second backscatter coefficient.

16. The system of claim 15, wherein a substantially similar scan setup is used to acquire the echo signal power spectrum of the reference phantom for the fundamental frequency band and the echo signal power spectrum of the tissue region for the fundamental frequency band.

17. The system of claim 15, further operable to:

storing the echo signal power spectrum of the second reference phantom for the fundamental frequency band and the echo signal power spectrum of the second reference phantom for the harmonic frequency band, an

The echo signal power spectrum of the reference phantom using the fundamental frequency band is determined for determining the first backscatter coefficient based on the correlation between the tissue region and the reference phantom, and the echo signal power spectrum of the reference phantom using the harmonic frequency band is determined for determining the second backscatter coefficient.

18. The system of claim 17, having acquired an echo signal power spectrum of a reference phantom in a fundamental frequency band and an echo signal power spectrum of a reference phantom in a harmonic frequency band using a first scan setting, the system to:

storing a second echo signal power spectrum of the reference phantom for the fundamental frequency band and a second echo signal power spectrum of the reference phantom for the harmonic frequency band, the second echo signal power spectrum being acquired using a second scan setting,

wherein the echo signal power spectrum of the tissue region of the fundamental frequency band and the echo signal power spectrum of the tissue region of the harmonic frequency band are acquired using a third scan setting, an

The system is for determining an echo signal power spectrum of a reference phantom using a fundamental frequency band for determining a first backscatter coefficient and an echo signal power spectrum of the reference phantom using a harmonic frequency band for determining a second backscatter coefficient based on a correlation between the first scan setting and the third scan setting.

Background

Conventional ultrasound imaging systems create an internal image (i.e., a B-mode image) of a volume by detecting acoustic impedance discontinuities within the volume. More specifically, conventional ultrasound imaging involves transmitting an ultrasound beam into a volume and detecting a return signal reflected from an acoustic impedance discontinuity within the volume. Since different materials typically exhibit different acoustic impedances, the detected acoustic impedance discontinuity is indicative of the location of the different materials within the volume.

The B-mode images described above depict qualitative features in tissue, but do not directly provide quantitative information about the tissue. On the other hand, the quantitative ultrasound system may determine the Attenuation Coefficient (AC) and the backscatter coefficient (BSC) of the region of interest (ROI). AC is a measure of the loss of ultrasound energy in the tissue and BSC is a measure of the ultrasound energy returned from the tissue. Quantitative ultrasound values such as these help characterize properties of the tissue such as hardness and fat fraction (fat fraction). Additional quantitative ultrasound measurements will further aid in these characterizations.

The AC and BSC determinations need to be compensated for the system effects of acquiring the ultrasound system. These effects include transmit pulse power, transducer sensitivity, beam focusing pattern (pattern), and depth dependent receiver gain. Conventionally, compensation involves dividing the echo signal power spectrum of the tissue sample in the fundamental frequency band by the echo signal power spectrum of a well-characterized reference phantom (phantom) in the fundamental frequency band from the same depth. The resulting quotient is a normalized spectrum that depends on the attenuation and backscatter properties of the tissue sample and the reference phantom. Since the properties of the reference phantom are known, the AC and BSC of the tissue sample can be derived from the normalized spectrum.

One drawback of the foregoing determination is the need to acquire reference phantom data at the time of the clinical scan. This additional acquisition hinders workflow and patient throughput. Furthermore, the accuracy of such determinations has been seen as lacking in many scenarios. The foregoing determinations also fail to provide other potentially useful quantitative measures, such as tissue non-linearity.

Drawings

Construction and use of embodiments will become apparent from consideration of the following description as illustrated in the accompanying drawings, in which like reference numerals designate like parts, and in which:

FIG. 1 is a block diagram of a quantitative ultrasound system according to some embodiments;

FIG. 2 is a flow diagram of a process for determining quantitative ultrasound values according to some embodiments;

figure 3 is a block diagram of an ultrasound system for acquiring reference phantom calibration data according to some embodiments;

figure 4 is a tabular representation of data used to determine reference phantom calibration data according to some embodiments;

FIG. 5 is an ultrasound image including quantitative ultrasound values according to some embodiments; and

figure 6 is a block diagram of an ultrasound system according to some embodiments.

Detailed Description

The following description is provided to enable any person skilled in the art to make and use the described embodiments, and sets forth the best mode contemplated for carrying out the described embodiments. Various modifications, however, will remain apparent to those skilled in the art.

Some embodiments provide for efficient and accurate determination of quantitative ultrasound values. More specifically, some embodiments provide an inventive system for determining AC and BSC based on echo signal power spectra from harmonic bands. The use of harmonic bands is more clinically desirable. The clinical benefit of using harmonic signals is the improved repeatability and reproducibility of QUS estimation due to reduced reverberation, clutter noise and phase aberrations.

Such embodiments may utilize a pre-stored echo signal power spectrum (or RF or IQ signal data from which the power spectrum may be calculated) of a well-characterized reference phantom in the harmonic frequency band, thereby eliminating the need to acquire calibration data at or near the time of clinical data acquisition.

Some embodiments advantageously determine a quantitative value of tissue nonlinearity. In contrast, the conventional system described above assumes that the non-linearity of the reference phantom is substantially equal to the non-linearity of the tissue in the ROI.

FIG. 1 illustrates an implementation according to some embodiments. The system 100 includes an ultrasound unit 110, an ultrasound transducer 120, and a display 130. The volume 140 may include a human body, but the embodiment is not limited thereto. The ultrasound transducer 100 may comprise any suitable ultrasound transducer, such as, but not limited to, a phased array, linear, or convex ultrasound transducer.

In general, the processing unit 112 of the unit 110 may execute program code to control the transducer 120 to transmit ultrasound beams into the volume 140 and to receive acoustic radio frequency signals therefrom. The processing unit 112 of the unit 110 may execute program code to generate an image and/or determine quantitative ultrasound values based on the received signals. The image and/or the determined value may be displayed to a technician on display 130.

According to some embodiments, a technician operates the system 100 to acquire echo signal power spectra of harmonic bands from the ROI of the volume 140. The obtaining may include: an RF or IQ signal is acquired and an echo signal power spectrum of a harmonic band is calculated therefrom. The acquisition is performed using first scan settings, which may include specific values for frequency, F-number/aperture size, focus and apodization (apodization) function parameters. The transducer 120 operates in conjunction with the transmit unit 116 to transmit ultrasound beams into the ROI, and the receiver unit 118 operates in conjunction with the transducer 120 to receive reflected signals in the harmonic bands from the ROI according to the scan settings.

Next, harmonic calibration data corresponding to the first scan setting is retrieved from the storage device 114. The harmonic calibration data may include an echo signal power spectrum of a harmonic frequency band acquired from the reference phantom using the same or substantially similar scan setting as the first scan setting (or data from which the echo signal power spectrum may be derived). The acquisition and storage of harmonic calibration data is described in detail below.

The echo signal power spectrum acquired from the volume 140 is normalized by dividing the echo signal power spectrum acquired from the volume 140 by the stored echo signal power spectrum. The result is a normalized spectrum that depends only on the attenuation and backscatter properties of the ROI tissue and the reference phantom. Since the attenuation and backscatter properties of the reference phantom are known, the AC and BSC of the tissue can be derived from the normalized spectrum, as will be described in detail below.

According to some embodiments, the echo signal power spectrum of the fundamental frequency band is also acquired from the ROI of the volume 140. The acquisition is performed using second scan settings, which may or may not be different from the first scan settings mentioned above. Fundamental calibration data corresponding to the second scan setting is retrieved from storage 114. The fundamental calibration data includes an echo signal power spectrum of a fundamental frequency band acquired from the reference phantom using the same or substantially similar scan settings as the second scan settings (or, as such, RF or IQ data from which the echo power signal spectrum can be derived).

The fundamental band echo signal power spectrum acquired from the volume 140 is normalized by dividing the fundamental band echo signal power spectrum acquired from the volume 140 by the fundamental calibration data, resulting in another normalized spectrum that depends only on the attenuation and backscatter properties of the ROI tissue and the reference phantom. The AC and BSC of the tissue may also be derived from the normalized spectrum.

According to some embodiments, the nonlinearity of the ROI may be determined based on the BSC derived from the harmonic band data and the BSC derived from the fundamental band data. This determination provides improved ROI characterization compared to conventional systems, which assume that the nonlinearities of the reference phantom and the ROI are equivalent.

Fig. 2 is a flow diagram of a process 200 for determining quantitative ultrasound values according to some embodiments. Process 200 may be performed by elements of system 100, but embodiments are not limited thereto. Process 200, and all other processes mentioned herein, may be embodied in processor-executable program code read from one or more non-transitory computer-readable media (such as a hard disk, volatile or non-volatile random access memory, DVD-ROM, flash drive, and magnetic tape) and then stored in a compressed, uncompiled, and/or encrypted format. In some embodiments, hardwired circuitry may be used in place of or in combination with program code to implement processes according to some embodiments. Thus, embodiments are not limited to any specific combination of hardware and software.

Initially, at S210, a reference phantom is scanned to acquire RF or IQ data, and echo signal power spectra of the fundamental and harmonic frequency bands are determined therefrom. The reference phantom is scanned using a particular scan setting. In some embodiments, additional echo signal power spectra for the fundamental and harmonic frequency bands are acquired at S210 using other scan settings.

Fig. 3 illustrates a system 300 for performing S210 according to some embodiments. The system 300 may be operated by an ultrasound system provider, phantom provider, or other non-clinical entity. The processing unit 312 of the ultrasound unit 310 executes a scanning program of the memory device 314 to control the transducer 320 to transmit signals to the phantom 340 and to receive signals from the phantom 340. The phantom 340 represents an intended ROI (e.g., an adult male torso), and the ultrasound unit 310 and transducer 320 may comprise production-equivalent versions of ultrasound units and transducers that are intended to be used in scanning the intended ROI. The storage device 314 stores the acquired power spectrum.

Next, at S220, the acquired echo signal power spectrum of the fundamental frequency band and the harmonic frequency band is stored in the ultrasound system. In some embodiments, the stored data includes data from which the power spectrum of the echo signal in the fundamental and harmonic frequency bands can be derived. In some examples, the spectra are stored as the fundamental and harmonic calibration data described above to be shipped to the customer's ultrasound system. According to some embodiments, the spectra are stored in association with scan settings used to acquire the respective spectra.

Fig. 4 is a tabular representation of the data stored at S220, according to some embodiments. Table 400 associates each acquired power spectrum with the scan settings and reference phantom used to acquire that power spectrum. As shown, at S210, more than one type of reference phantom may be scanned. Each reference phantom/scan setting pair is associated with fundamental and harmonic band power spectrum data. The value of the spectrum data column may be composed of a file name of a file including the corresponding spectrum data.

In some embodiments, S210 and S220 are performed during a time period that is well before clinical use of the data acquired therein (e.g., before shipping the ultrasound system to a clinic). Thus, the dashed arrow between S220 and S230 indicates a time lapse that may be significantly longer than the time between other adjacent steps of the process 200.

At S230, the ultrasound system in which the spectra are stored is operated to acquire echo signal power spectra of the fundamental and harmonic bands from the ROI, for example, in a clinical setting. The acquisition uses a first scan setting for generating calibration data for the corresponding reference phantom at S210. In some embodiments, the first scan setting is set as a default scan setting for the ultrasound system.

According to some embodiments of S230, the ultrasound system transmits signals at a center frequency of 3 MHz and a frequency bandwidth from 2 to 4 MHz. The fundamental signal is then received in the 2-4 MHz range. To obtain a signal in the harmonic band, the signal is transmitted at a center frequency of 1.5 MHz and has a bandwidth between 1-2 MHz. The resulting received harmonic signals may exhibit, for example, a frequency band of twice the center frequency or between 2-4 MHz. The subsequent calculation of the QUS value is therefore associated with frequencies between 2-4 MHz.

Next, at S240, stored calibration data corresponding to the first scan setting is determined. The determined calibration data consists of echo signal power spectra of fundamental and harmonic bands acquired using the reference phantom corresponding to the ROI and the first scan setting. For example, S240 may include: appropriate reference phantom and scan settings are identified within one row of table 400, and stored fundamental and harmonic calibration data files identified within the same row of table 400 are acquired.

At S250, a first AC and a first BSC are determined. The determination is based on the echo signal power spectrum of the fundamental frequency band acquired at S230 and the calibrated echo signal power spectrum of the fundamental frequency band determined at S240. The embodiment is not limited to the following description of the determination at S250.

Initially, each radio frequency echo line of the ROI is divided into several overlapping time-gated windows. A fourier transform is applied to each window and the power spectra of the windows corresponding to the same depth are averaged. The same procedure is performed for the corresponding ROI of the reference phantom. In standard pulse echo imaging, the measured power spectrum in the fundamental frequency band of a windowed region in statistically homogeneous tissue is given by equation (1):

（1）。

subscriptsThe sample (i.e., the tissue of the ROI) is represented. The distance from the transducer surface to the center of a particular time-gated window within the ROI is determined byzAre indicated. Frequency is controlled byfAre indicated.T(f) Representing the transfer function of the transmitted pulse.E _tx (f) AndE _rx (f) Representing the transducer electro-acoustic and acoustic-electric transfer functions, respectively.D(f,z) Diffraction effects are indicated, which are related to the transducer geometry and the transmit and receive focusing.AndBSC _s (f) Respectively, the frequency dependent AC and BSC values of the samples.

Similarly, the power spectrum of the backscattered signal from the reference phantom is:

（2）。

dividing the power spectrum of the sample by the power spectrum of the reference phantom yields:

（3）。

compensating for the known attenuation and backscatter properties of the reference phantom, equation (3) becomes:

（4）。

calculating the natural logarithm yields:

（5）。

the slope (-4) of the line of equation (5) can then be fitted from the alignment depth z) And intercept (ln: (BSC _s (f) ) derived from the received signal) to derive an attenuation coefficient(np/cm) and backscattering coefficientBSC _s （1/cm-str）。

At S260, a second AC and a second BSC are determined. The determination at S260 is based on the echo signal power spectrum of the harmonic band acquired at S230 and the calibration echo signal power spectrum of the harmonic band determined at S240. The embodiment is not limited to the following description of the determination at S260.

Estimating AC and BSC using harmonic bands requires a new model that accounts for tissue non-linearity. From fundamental frequencyfPlane wave ofP ₀Is given by:

（6），

whereinAndare the attenuation coefficients (np/cm) of the fundamental and harmonic signals, respectively, and K is a constant proportional to the non-linearity parameter B/a.

The ratio term in equation (6) can be further simplified using a taylor series of exponential functions:

，

wherein the last step uses common assumptionsAnd taylor series approximation.

In the case of focused transmission using a clinical transducer array,P ₀(f) Is modeled as:

（8），

whereinT(f) Is the transfer function of the transmitted pulse and,E _tx (f) Is an electro-mechanical (electro-mechanical) transfer function at emission, andD _tx (f) Is the diffraction pattern upon emission. Using equations (7) and (8):

（9）。

the power spectrum of the received second harmonic signal is given by:

（10），

whereinE _rx (f) Is an electro-mechanical transfer function upon reception, andD _rx (f) Is the diffraction pattern at the time of reception,BSC(2f) Is the backscattering coefficient (np) at the second harmonic frequency/cm-str) andaccounting for the attenuation of the return harmonic signal. Combining equations (9) and (10):

（11）。

in Tissue Harmonic Imaging (THI) mode, the radio frequency signals from two pulses that are 180 ° out of phase are summed to obtain a harmonic signal.

Each radio frequency echo line of the ROI is divided into several overlapping time-gated windows. A fourier transform is applied to each window and the power spectra of the windows corresponding to the same depth are averaged. The same procedure is performed for the corresponding ROI of the reference phantom.

The power spectra of the samples and the reference in the ROI are given by equation (11). It is assumed that the terms in parentheses are the same for both the sample and the reference. By calculating the ratio of the power spectra from the sample and the reference, we obtain an equation similar to equation (3):

（12）。

compensating for the known attenuation, backscatter, and non-linearity of the reference phantom, equation (12) becomes:

（13）。

calculating the natural logarithm yields:

（14）。

the frequency can be derived from the slope of the line fitting equation (14) to the alignment depth z2fLower attenuation coefficient(dB/cm). Fitting the intercept of the line of equation (14) against the depth z yields the term from the non-linearityBiased ln (BSC _s (2f))。

Returning to process 200, at S270, the non-linearity of the ROI is determined based on the first BSC determined at S250 and the second BSC determined at S260. Continuing with the example above, ln can be measured by using the fundamental band based on equation (5) ((s))BSC _s (2f) Wherein the fundamental frequency is now2f) And substituting the result into equation (14), thereby estimating the non-linearity term in equation (14)。

At S280, an image of the ROI is generated and displayed. The image may be generated based on one or both of the spectra acquired at S230, as is known in the art. The image may also indicate non-linearity and any other values determined based on the received signal.

Fig. 5 illustrates an image 500 generated and displayed at S280 according to some embodiments. As shown, the determined values of shear wave velocity (Vs), elasticity (E), AC, BSC, Ultrasonically Derived Fat Fraction (UDFF), and nonlinearity (K) are displayed simultaneously with the ultrasound B-mode image data. These quantitative measurements can improve the diagnostic capabilities of medical ultrasound by removing qualitative interpretations of B-mode images and by reducing system-related factors.

The estimation of AC based on the fundamental and harmonic bands should be equivalent. Thus, the image 500 may display either the average or the estimated value of the two. In some embodiments, variability may be reduced by determining and displaying a weighted average of the two AC estimates.

In the case of a BSC, the BSC value determined at S260 based on the harmonic band is biased by a non-linearity term. Accordingly, the BSC displayed at S280 may be the BSC value determined at S250 based on the base band. If the non-linearity term is assumed to be negligible, the average of the two BSC values may be displayed.

Fig. 6 is a block diagram of an ultrasound imaging system 600 according to some embodiments. System 600 may implement one or more processes described herein. System 600 is a phased array ultrasound imaging system, but embodiments are not so limited. Typical phased array systems utilize 64 to 256 receive channels and a significant number of transmit channels. For clarity, fig. 6 illustrates a single transmit and receive channel.

The system 600 includes a transducer element 605 and a transmit/receive switch 610. The transducer elements 605 may comprise a 1-dimensional, 1.25-dimensional, 1.5-dimensional, 1.75-dimensional, or 2-dimensional array of elements of a piezoelectric or capacitive membrane element. Transmit/receive switch 610 is operated to allow ultrasound energy to be transmitted via element 605 (e.g., in response to application of a voltage across element 605) or to allow voltages to be received generated by element 605 in response to received ultrasound energy (i.e., echoes).

The transmit beamformer 615, in conjunction with the digital-to-analog converter 620 and the high voltage transmitter 625, is operable to generate waveforms for a plurality of channels, where each waveform may exhibit a different amplitude, delay, and/or phase. The receive beamformer 630 receives signals from multiple channels, each of which may be subject to amplification 635, filtering 640, analog-to-digital conversion 645, delay and/or phase rotators, and one or more summers. The receive beamformer 630 may be configured by hardware or software to apply relative delays, phases and/or apodization in response to each transmit beam to form one or more receive beams. The receive beamformer 630 may provide dynamic receive focusing, as well as fixed focus reception, as is known in the art.

The receive beams formed by the receive beamformer 630 represent the material through which the transmit and receive beams have passed. The receive beams are output to processor 650 for processing. For example, the processor 650 may generate an image based on the receive beams.

The processor 650 may execute processor-executable program code stored in the memory 660 to perform and/or control other components of the system 600 to perform processes described herein. The processor 650 may include a B-mode detector, a doppler detector, a pulsed wave doppler detector, a correlation processor, a fourier transform processor, an application specific integrated circuit, a general purpose processor, a control processor, an image processor, a field programmable gate array, a digital signal processor, analog circuitry, digital circuitry, combinations thereof, or other now known or later developed devices for generating data (e.g., image data) based on beamformed ultrasound samples.

The memory 660 may include non-transitory computer-readable storage media, such as random access memory and/or non-volatile memory (e.g., flash memory, hard disk memory). Memory 660 may store program code, calibration data, B-mode images, and/or any other suitable data. Display 655 may include a cathode ray tube display, a liquid crystal display, a light emitting diode display, a plasma display, or other type of display for displaying images and/or measurements.

Those skilled in the art will appreciate that various adaptations and modifications of the just-described embodiments can be configured without departing from the scope and spirit of the claims. It is therefore to be understood that the claims may be practiced otherwise than as specifically described herein.