JPWO2020128609A5 - - Google Patents

Claims (18)

A locally varying nonlinear elastic parameter (NEP) of a material within a spatial estimation region (SER) as a function of the material's position within the SER from a set of measured nonlinear propagation delays (NPD) within the SER A method of estimating from spatially-varying NEP values of by using a mathematical model that produces a spatially-varying model NPD in said SER, said method comprising:
a) measuring said NPD as a function of position within said SER, said measuring comprising:
- transmitting at least two pulse complexes composed of overlapping low frequency (LF) and high frequency (HF) pulses along overlapping LF and HF transmission beams within at least said SER;
- HF reception from scattered HF pulses from object structures in a set of depth regions along the HF transmit beam in the SER from at least two transmit pulse complexes with different LF pulses along the HF transmit beam. record the signal,
- said along said HF transmit beam within said SER comparing HF received signals scattered from said HF pulses of pulse complexes having different LF pulses from said set of depth regions along said HF transmit beam; by generating an estimate of the NPD at a set of depth regions;
b) with a set of NEPs as input,
i) a distance function of the difference between the measured NPD and the model NPD for the NEP value weighted by a spatially variable distance weight;
ii) generating an estimation function (EF) that provides a weighted sum of the NEP value in the SER with a measure of local variation weighted by a spatially variable variation weight;
c) for a given set of measured NPDs, minimize the EF with respect to the set of NEPs, and vary spatially within the SER using the set of NEPs that minimize the EF; A method comprising generating an estimate of NEP. The local values of the range weight and the variation weight are i) an estimate of the strong local reflectors in the received HF signal and ii) an estimate of the local magnitude of the multiply scattered HF noise relative to the local magnitude of the primary scattered HF signal. 2. The method of claim 1, deduced from one or both of: The EF is minimized over the set of NEPs subject to one or both of i) a maximum constraint on the estimated local NEP and ii) a minimum constraint, subject to the maximum and the minimum constraint. 2. The method of claim 1, wherein the set of NEPs starting with the EF is used to generate estimates of spatially varying NEPs in the SER. The distance weight is generated as a ratio of a narrow area mean value to a wide area mean value of the envelope of the received HF signal in the SER, the variation weight is generated as a positive function of the distance weight, and the 2. The method of claim 1, wherein the derivative of the positive function is negative. 2. The method of claim 1, wherein said estimate of local magnitude of multiply scattered HF noise relative to said local magnitude of said primary scattered HF signal is obtained from said measured NPD. 4. wherein said estimate of said local magnitude of multiple scattered HF noise relative to said local magnitude of said primary scattered HF signal is obtained from said value of said measured NPD and is less than a fraction of an expected limit. 5. The method described. The HF receive signals that measure the NPD are: i) a set of HF receive beams that traverse the HF transmit beam at different depths along the HF transmit beam; 2. The method of claim 1, derived from one or both of using an HF receive signal having a beam axis and gating intervals of the HF backscatter receive signal at different depths along the HF transmit beam. wherein said distance function is based on a function f(x) of the value x of the difference between said measured output and said model output at each point of said SER, wherein the sign of the derivative of f(x) is equal to the sign of x. Item 1. The method according to item 1. The measured NPD is further processed and used for correction of the HF receive signal for each transmit beam to yield an HF receive signal after correction for each transmit beam, wherein at least two corrected HF receive The signals are for each transmit beam combined to produce one or both of i) an HF receive signal with suppression of multiple scattering noise and ii) an HF receive signal with suppressed linear scattering and enhanced nonlinear scattering. 2. The method of claim 1, wherein The synthetic lateral focusing of said HF receive range cells is obtained at multiple depths by lateral filtering of said HF receive signal for multiple transmissions with a set of filter coefficients, said filter coefficients being i) by calculating the product of said HF transmit beam and said HF receive beam using a constant of space and ii) an ultrasonic propagation velocity that is one of a function of said spatially varying NEP estimate. 1. The method of claim 1. 2. The method of claim 1, wherein the determination of the distance weights and the variation weights is performed by machine learning in the form of differential programming of the received HF signal to the type of material object under study. A locally varying nonlinear elastic parameter (NEP) of a material within a spatial estimation region (SER) as a function of the material's position within the SER from a set of measured nonlinear propagation delays (NPD) within the SER. An instrument for estimating by use of a mathematical model to generate a spatially varying model NPD in said SER from spatially varying NEP values, said instrument comprising:
a) a multi-element ultrasound probe comprising:
- transmitting overlapping LF and HF pulses along overlapping low frequency (LF) and high frequency (HF) transmit beams at least within said SER;
- a multi-element ultrasound probe for recording HF element receive signals from HF pulses scattered from object structures in said SER from at least two transmit pulse complexes with different LF pulses along each HF transmit beam. have
b) a multi-channel front end unit providing HF and LF drive signals for said multi-element probe for transmitting said LF and said HF pulse complexes and for receiving HF element receive signals from said multi-element probe; c) the HF receive beam-former, the HF receive beam-former receiving HF receive signals from multiple depths along the HF transmit beam; and transmitting said HF receive signal to d) a measurement unit setup, said measurement unit setup for HF reception for said multiple depths along each HF transmit beam from at least two different pulse complexes comparing a signal to the difference of the LF pulses to provide measured NPDs for the multiple depths along the HF transmit beam, and e) communicating the measured NPDs to an estimation unit , the estimation unit performing the generating an estimate of the spatially varying NEP within the spatial estimation region from the measured NPE, the estimation unit comprising:
- with a set of NEPs as input, i) a distance function of the difference between the measured NPD and the model NPD for the NEP values weighted by a spatially variable distance weight, and ii) a spatially variable generating an estimation function (EF) that gives a weighted sum of the measured local variation of the NEP value in the SER weighted by the variation weight of
- for a given set of measured NPDs, minimize the EF with respect to the set of NEPs, and use the set of NEPs that minimize the EF to spatially vary the NEPs within the SER; An instrument configured to produce an estimate of . the estimation unit from one or both of: i) an estimate of strong local reflectors in the received HF signal; 13. The method of claim 12, configured to generate local values of distance weights and said variation weights. The HF receive beam-former unit converts the HF receive signals from multiple depths along the HF transmit beams to: i) from a set of HF receive beams that intersect the HF transmit beams at the multiple depths; ii) by one or both of gating intervals at said multiple depths of a backscattered HF signal from an HF receive beam with a beam axis located near said beam axis of said transmit beam. 13. Apparatus according to clause 12 . The measured NPD is further processed and used to modify the HF received signal for each transmit beam to yield a modified HF received signal for each transmit beam, wherein at least two modified HF received signals for each transmit beam combined to produce one or both of i) an HF receive signal with suppression of multiple scattering noise and ii) an HF receive signal in which linear scattering is suppressed and nonlinear scattering is promoted. 13. The apparatus of claim 12 , comprising: 13. The apparatus of claim 12 , wherein at least one of i) the HF receive beam-forming unit, ii) the measurement unit, and iii) the estimation unit is embodied as software on a programmable computer. 12. The apparatus of claim 11, further comprising a unit for enabling a composite focus of said HF receive range cells to be obtained at multiple depths by lateral filtering of said HF receive signals for multiple transmit beams. 13. The apparatus of claim 12 , wherein the determination of said distance weights and said variation weights is performed by machine learning in the form of differential programming of said received HF signal to the type of material object under study.