Methods for ultrasound system independent attenuation coefficient estimation

Patent metadata

Field	Value
Publication number	US-12089996-B2
Application number	US-201816625910-A
Country	US
Kind code	B2
Filing date	Jun 22, 2018
Priority date	Jun 23, 2017
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

Systems and methods for estimating acoustic properties in a region-of-interest in a subject or other object being imaged using a reference frequency method (“RFM”) is described. Using this RFM technique, ultrasound data acquired at a given frequency are normalized by ultrasound data acquired at different frequencies (e.g., adjacent frequencies or otherwise) in order to provide estimations of the acoustic properties (e.g., attenuation coefficient, a backscatter coefficient, or both) that are independent of the ultrasound system used to acquire the underlying data. For instance, the amplitude of each frequency component can be normalized by a different frequency in the power spectrum to cancel out the system-dependent effects. Because the methods described in the present disclosure are system independent, they can be applied to any transducer geometry (e.g., linear or curved arrays) and using any beam pattern (e.g., focused or unfocused).

First claim

The invention claimed is:

1. A method for estimating an acoustic property of a physical medium in a region-of-interest using an ultrasound system, the steps of the method comprising:
(a) transmitting ultrasound to the region-of-interest using a transducer of the ultrasound system, wherein the ultrasound is transmitted in a single transmission event with a bandwidth comprising a single center frequency, wherein the bandwidth contains a first frequency and a second frequency that is different from the first frequency, wherein the ultrasound is transmitted at each frequency in the bandwidth using a same aperture of the transducer;
(b) acquiring ultrasound data from a plurality of depth locations along an ultrasound beam path within the region-of-interest using the transducer of the ultrasound system, the ultrasound data comprising at least first ultrasound data acquired in response to the ultrasound transmitted to the region-of-interest at the first frequency and second ultrasound data acquired in response to the ultrasound transmitted to the region-of-interest at the second frequency, wherein the first ultrasound data comprise a first power spectrum of backscattered radio frequency (RF) signals and the second ultrasound data comprise a second power spectrum of backscattered RF signals;
(c) computing a plurality of frequency spectra ratio values by computing a ratio between the first power spectrum in the first ultrasound data and the second power spectrum in the second ultrasound data acquired at each of the plurality of different depth locations;
(d) estimating an acoustic property value of a physical medium in the region-of-interest from the plurality of frequency spectra ratio values; and
(e) generating a report based on the estimated acoustic property value of the physical medium.

2. The method as recited in claim 1 , wherein the acoustic property value is an attenuation coefficient.

3. The method as recited in claim 2 , wherein estimating the attenuation coefficient includes computing logarithm values by computing a logarithm of the frequency spectra ratio values, forming a frequency spectra ratio decay curve by arranging the logarithm values as a function of depth location, computing a slope over a portion of the frequency spectra ratio decay curve, and estimating the attenuation coefficient based on the slope.

4. The method as recited in claim 3 , wherein the slope is computed based on a linear fitting.

5. The method as recited in claim 4 , wherein a reliability of the attenuation coefficient is estimated based on a residual error of the linear fitting.

6. The method as recited in claim 4 , wherein the portion of the frequency spectra ratio decay curve is selected as a range of depth locations over which the frequency spectra ratio decay curve follows a linear decrease as a function of depth location at the first frequency.

7. The method as recited in claim 3 , wherein the slope is computed based on a nonlinear fitting.

8. The method as recited in claim 7 , wherein the nonlinear fitting is computed based in part on a variable projection (VARPRO) method.

9. The method as recited in claim 2 , wherein estimating the attenuation coefficient includes computing logarithm values as a logarithm of the plurality of frequency spectra ratio values and fitting the logarithm values to a parametric model to estimate the attenuation coefficient.

10. The method as recited in claim 9 , wherein the parametric model is a one-parameter model of frequency spectra ratio and estimating the attenuation coefficient includes normalizing the plurality of frequency spectra ratio values by reference depth data before computing the logarithm values.

11. The method as recited in claim 10 , wherein the reference depth data are ultrasound data acquired at the first frequency at one or more reference depths.

12. The method as recited in claim 9 , wherein the parametric model is a two-parameter model of frequency spectra, and estimating the attenuation coefficient also includes estimating a backscatter coefficient.

13. The method as recited in claim 12 , wherein step (b) is repeated using at least one of different first and second frequency values or different depth locations in each transmission event, such that the plurality of frequency spectra ratios correspond to at least one of multiple frequency measurements or multiple depth measurements.

14. The method as recited in claim 9 , wherein fitting the logarithm values to the parametric model includes using a least-squares estimation.

15. The method as recited in claim 9 , wherein fitting the logarithm values to the parametric model includes constraining the fitting using a constraint.

16. The method as recited in claim 15 , wherein the constraint is a physical medium constraint that defines an expected range of attenuation coefficient values for the physical medium.

17. The method as recited in claim 15 , wherein the constraint is a data generated constraint that is an adaptively determined constraint based at least in part on the frequency spectra ratio values.

18. The method as recited in claim 1 , wherein step (b) is repeated for a plurality of different first frequency and second frequency values in each transmission event, step (c) is repeated for each of the plurality of different first frequency and second frequency values, and step (d) includes estimating a different acoustic property value for each of the plurality of different first frequency values and estimating a final acoustic property value based on a combination of the different acoustic property values.

19. The method as recited in claim 18 , wherein the combination of the different acoustic property values includes averaging the different acoustic property values.

20. The method as recited in claim 19 , wherein the different acoustic property values are averaged using a weighted averaging.

21. The method as recited in claim 1 , wherein the acoustic property value is a backscatter coefficient.

22. The method as recited in claim 21 , wherein estimating the backscatter coefficient includes computing logarithm values by computing a logarithm of the frequency spectra ratio values, forming a frequency spectra ratio decay curve by arranging the logarithm values as a function of depth location, computing a y-intercept of the frequency spectra ratio decay curve, and estimating the backscatter coefficient based on the y-intercept of the frequency spectra ratio decay curve.

23. The method as recited in claim 22 , wherein arranging the plurality of frequency spectra ratio values as a function of depth location includes providing transducer response data to the computer system, computing a transducer response ratio, and weighting the plurality of frequency spectra ratio values based on the transducer response ratio.

24. The method as recited in claim 23 , further comprising computing a slope of the frequency spectra ratio decay curve and estimating an attenuation coefficient value based on the slope.

25. The method as recited in claim 1 , wherein the first frequency is spectrally adjacent to the second frequency.

Assignees

• Mayo Found Medical Education & Res

Inventors

• Gong Ping
• Song Pengfei
• Chen Shigao
• Trzasko Joshua D

Classifications

• G01S15/892

  the array being curvilinear · CPC title

• G01N2291/02475

  Tissue characterisation · CPC title

• G01N2291/015

  Attenuation, scattering · CPC title

• G01N29/46

  by spectral analysis, e.g. Fourier analysis {or wavelet analysis (spectral signal processing per se G06F17/14)} · CPC title

• G16H50/30

  for calculating health indices; for individual health risk assessment · CPC title