No abstract

Objectives Accurately measuring the attenuation coefficient (AC) of reference phantoms is critical in clinical applications of quantitative ultrasound. Phantom AC measurement requires proper compensation of membrane transmission loss. Conventional methods require separate membrane samples to obtain membrane transmission loss. Unfortunately, separate membrane samples are often unavailable. A pulse‐echo approach is proposed herein to compensate for membrane transmission loss without requiring separate membrane samples. Methods The proposed method consists of the following steps. First, the insertion loss, caused by phantom attenuation and membrane transmission loss, is measured. Second, the membrane reflection coefficient is measured. Third, the unknown acoustic parameters of the membrane and phantom material are estimated by fitting theoretical reflection coefficient to the measured one. Finally, the fitted parameters are used to estimate membrane transmission loss and phantom AC. The proposed method was validated through k‐Wave simulations and phantom experiments. Experimental AC measurements were repeated on 5 distinct phantoms by 2 operators to assess the repeatability and reproducibility of the proposed method. Five transducers were used to cover a broad bandwidth (0.7–16 MHz). Results The acquired AC in the simulations had a maximum error of 0.06 dB/cm‐MHz for simulated phantom AC values ranging from 0.5 to 1 dB/cm‐MHz. The acquired AC in the experiments had a maximum error of 0.045 dB/cm‐MHz for phantom AC values ranging from 0.28 to 1.48 dB/cm‐MHz. Good repeatability and cross‐operator reproducibility were observed with a mean coefficient of variation below 0.054. Conclusion The proposed method simplifies phantom AC measurement while providing satisfactory accuracy and precision.

Attenuation of reference phantoms that are used in quantitative ultrasound applications must be accurately measured. In this regard, we recently proposed an insertion-based planar reflection technique to simultaneously estimate membrane transmission loss and phantom attenuation. Simulating the measurement procedure can assist with validating and improving the methodology and gauge its accuracy and precision by carefully controlling the simulation's setup parameters. For simulation, a pulse echo setup with a single element transducer immersed in water was implemented in k-Wave. First, a reference plane with known acoustic properties is positioned at the focus, yielding the reference echo that models transducer diffraction and frequency response. Next, a phantom covered by a thin layer of acoustic windowing membrane is inserted between the transducer and reference plane, yielding the insertion echo that captures the phantom attenuation and membrane transmission loss. Finally, the phantom top surface, lined with the membrane, is positioned at the focus, thereby yielding the surface echo that captures the membrane reflectivity. Spectral analysis of the three echoes estimates the membrane transmission-loss-corrected phantom attenuation. Preliminary simulation of a phantom with predefined attenuation coefficient of 0.6–0.9 dB/cm MHz yielded a root mean square error of 0.06 dB/cm MHz over 3–5 MHz. [NIH Support: R01CA226528, R01DK106419, and R01HD089935.]