In Situ Calibration to Account for Transmission Losses in Backscatter Coefficient Estimation

Trong Nguyen, Alexander Tam, Michael L. Oelze

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

Abstract

The backscatter coefficient (BSC) has demonstrated the ability to classify disease state and to monitor changes in tissue due to therapy. However, traditional methods of estimating the BSC in vivo using a reference phantom technique do not account for transmission losses due to intervening layers between the ultrasonic source and tissue region to be interrogated. The intervening layers result in increases in bias and variance of BSC-based estimates. To accurately account for the transmission losses, an in situ calibration approach is proposed to obtain a more robust estimate of the BSC. The in situ calibration technique employs the use of a biocompatible sphere that is well-characterized ultrasonically and embedded inside a sample or tissue. Ultrasound scattered from the sphere encounters the same transmission loss and attenuation as the investigated sample and can be used as a reference spectrum to provide a more accurate estimate of the BSC. A 2-mm diameter titanium sphere was embedded inside a homogeneous phantom containing glass bead scatterers with diameters ≤ 90 μm placed spatially at random. A layer of fatty meat was placed on top of the phantom to produce transmission losses from a layer. The BSC was estimated from the phantom with and without the layer on top and compared using a traditional reference phantom technique and using the in situ sphere as a calibration target. Estimates of the effective scatterer diameter (ESD) were obtained for each condition and compared. The BSCs estimated using the in situ calibration approach with and without the layer present overlapped with the BSC estimated using the traditional reference phantom approach without the layer present. The BSC estimated using the traditional reference phantom approach with the layer present did not overlap with the other curves. Estimates of the ESD were 80 μm, 82 μm, 84 μm and 95 μm using the in situ calibration approach without the layer, with the layer and using the reference phantom approach without layer and with the layer present, respectively. The results indicate that an in situ calibration target can account for overlying tissue losses thereby improving the robustness of BSC-based estimates. This work was supported by a grant from the NIH (R21 EB020766).

Original languageEnglish (US)
Title of host publication2018 IEEE International Ultrasonics Symposium, IUS 2018
PublisherIEEE Computer Society
ISBN (Electronic)9781538634257
DOIs
StatePublished - Dec 17 2018
Event2018 IEEE International Ultrasonics Symposium, IUS 2018 - Kobe, Japan
Duration: Oct 22 2018Oct 25 2018

Publication series

NameIEEE International Ultrasonics Symposium, IUS
Volume2018-October
ISSN (Print)1948-5719
ISSN (Electronic)1948-5727

Other

Other2018 IEEE International Ultrasonics Symposium, IUS 2018
CountryJapan
CityKobe
Period10/22/1810/25/18

Keywords

  • QUS estimates
  • in-situ calibration
  • reference-free

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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    Nguyen, T., Tam, A., & Oelze, M. L. (2018). In Situ Calibration to Account for Transmission Losses in Backscatter Coefficient Estimation. In 2018 IEEE International Ultrasonics Symposium, IUS 2018 [8580156] (IEEE International Ultrasonics Symposium, IUS; Vol. 2018-October). IEEE Computer Society. https://doi.org/10.1109/ULTSYM.2018.8580156