Technique to compensate for unknown laminate transmission loss in phantom attenuation measurements | IEEE Conference Publication | IEEE Xplore

Technique to compensate for unknown laminate transmission loss in phantom attenuation measurements


Abstract:

It is important to accurately calibrate the acoustic parameters of reference phantoms used in quantitative ultrasound (QUS) applications. However, laminate membranes used...Show More

Abstract:

It is important to accurately calibrate the acoustic parameters of reference phantoms used in quantitative ultrasound (QUS) applications. However, laminate membranes used on the exterior of the phantoms complicate the attenuation coefficient (AC) measurements by introducing transmission loss. The existing through-transmission method addresses this issue by characterizing additional and separate membrane and phantom material specimens to estimate the membrane transmission loss. An alternative and simpler method is proposed, that uses a single phantom to simultaneously measure the membrane transmission loss and phantom AC. This is achieved using a single-element transducer in a broadband pulse-echo setup in three steps. Firstly, signal loss due to phantom insertion (insertion loss), composed of phantom attenuation and membrane transmission loss, is measured. Secondly, the membrane reflection coefficient is measured by comparing the echo from membrane surface to the echo from of a well-studied surface such as Plexiglas. Furthermore, the measured membrane reflection coefficient is compared with the theoretical membrane reflection coefficient to estimate the unknown acoustic parameters of the membrane and phantom material. Finally, these parameters are used in estimating the membrane transmission loss, which, in turn, is used to estimate the phantom AC from the insertion loss obtained in the first step. Two phantoms were used to validate the proposed method. AC of both phantoms were measured using the existing method, yielding a range of 0.5-1.2 dB/cm-MHz over 1.6-6.4 MHz. The AC estimates acquired using the proposed method showed good agreement with the existing method. Between the two methods, a root mean square AC difference of 0.006 dB/cm-MHz for the first phantom and 0.014 dB/cm-MHz for the second phantom was observed
Date of Conference: 07-11 September 2020
Date Added to IEEE Xplore: 17 November 2020
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Conference Location: Las Vegas, NV, USA

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I. Introduction

Phantoms with tissue mimicking material (TMM) are widely used to test and validate general ultrasound (US) imaging systems. They have added significance in quantitative ultrasound (QUS) applications, where they are used as references in removing the diffraction effects of the transducer array [1]. This reference phantom technique demands accurate calibration of phantom acoustic properties such as attenuation coefficient (AC), backscatter coefficient (BSC) and sound speed. Typically, the phantoms are lined with protective thin membranes on their external surface that complicate this calibration. Specifically, the transmission loss due to the membrane is nonnegligible and can introduce errors in the through-transmission phantom AC measurement if the transmission loss is not properly compensated for. The existing through-transmission methods [2] [3] compensate the membrane transmission loss by characterizing acoustic parameters of separate membrane and phantom material samples. However, this additional step complicates the calibration process since separate membrane and phantom material samples are not always freely available. Therefore, a new and simpler method is proposed that simultaneously estimates membrane transmission coefficient and phantom AC using a single phantom. Additionally, the paper validates the proposed method with respect to the existing method through phantom experiments.

References

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