Backscatter Coefficient Estimation Bias under Acoustic Nonlinearities

Andres Coila, Michael Oelze

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The backscatter coefficient (BSC) describes the scattering properties of a medium and can be used to characterize tissue. To calculate the BSC a calibration spectrum is required, which can be acquired using either a reference phantom method (RPM) or the planar reflector method (PRM). Although ultrasonic propagation is quasilinear at low acoustic pressures, for high acoustic pressures, acoustic nonlinear distortion becomes prevalent. Because water is low loss, use of the PRM method may introduce significant nonlinearities to the BSC estimation. In this study, we assessed the effects of the acoustic nonlinearities on BSC estimation when using the RPM and the PRM. Phantoms were scanned by exciting a single-element focused transducer (f/2) using one excitation level from low-power (LP) equipment (5800 PR, Panametrics Olympus, USA) and six excitation levels (EL1 to EL6) from high-power (HP) equipment (RAM-5000, Ritec, USA). This resulted in scanning the phantoms with increasingly higher pressures, but still within FDA limits for diagnostic ultrasound. The two phantoms, labelled phantoms A and B, had glass beads with diameters in the range 75-90 and 9-43 μm, respectively. The BSCs estimated with the LP system were used as a baseline. The normalized root-mean-squared error (RMSE) was calculated from BSCs estimated using the HP system with respect to the baseline. The BSC was parameterized to estimate the effective scatterer diameters (ESD) for each phantom using Faran's scattering theory. The BSC estimates resulted in smaller variations versus excitation levels for the RPM compared to the PRM. In the PRM, the RMSE was 0.62 ± 0.42 and 0.98 ± 0.77 for phantoms A and B, respectively; whereas, in the RPM, the RMSE was 0.21 ± 0.06 and 0.25 ± 0.12 for phantoms A and B, respectively. The ESD for the phantom A using the PRM decreased from 75 μm for EL1 to 39 μm for EL6; and using the RPM the ESD was 74.7 ± 2.3 μm across all settings. The ESD for the phantom B using the PRM decreased from 47 μm for EL1 to 0.5 μm for EL6; and using the RPM the ESD was 39.2 ± 5.6 μm across all settings. The RPM method was more robust against nonlinear distortion compared to the PRM because the PRM was used in water, where low loss resulted in large nonlinear distortion of the reference pulse.

Original languageEnglish (US)
Title of host publication2019 IEEE International Ultrasonics Symposium, IUS 2019
PublisherIEEE Computer Society
Pages2019-2022
Number of pages4
ISBN (Electronic)9781728145969
DOIs
StatePublished - Oct 2019
Event2019 IEEE International Ultrasonics Symposium, IUS 2019 - Glasgow, United Kingdom
Duration: Oct 6 2019Oct 9 2019

Publication series

NameIEEE International Ultrasonics Symposium, IUS
Volume2019-October
ISSN (Print)1948-5719
ISSN (Electronic)1948-5727

Conference

Conference2019 IEEE International Ultrasonics Symposium, IUS 2019
CountryUnited Kingdom
CityGlasgow
Period10/6/1910/9/19

Keywords

  • Backscatter coefficient
  • nonlinearity parameter
  • quantitative ultrasound

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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  • Cite this

    Coila, A., & Oelze, M. (2019). Backscatter Coefficient Estimation Bias under Acoustic Nonlinearities. In 2019 IEEE International Ultrasonics Symposium, IUS 2019 (pp. 2019-2022). [8926055] (IEEE International Ultrasonics Symposium, IUS; Vol. 2019-October). IEEE Computer Society. https://doi.org/10.1109/ULTSYM.2019.8926055