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

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