Prostate ablation treatment planning using high intensity focused ultrasound-based elasticity mapping

Ultrasound (US)-guided high intensity focused ultrasound (HIFU) ablation for prostate cancer (PCa) relies on defining accurate tumor margins prior to treatment. Shear wave elastography (SWE) is one emerging tool demonstrating high accuracy in outlining stiff PCa tissue. However, endorectal SWE has a limited effective push depth and lacks integration with clinical HIFU devices. To navigate these limitations, two HIFU-push methods of SWE were established using a transrectal HIFU array (128 elements, 1.6 MHz) coaxially integrated with an US imaging probe. In the first method, the HIFU array is used to generate a localized push at its focus and launch a longitudinal shear wave (LSW) propagating along the HIFU axis, which are then tracked by pulses from the imaging probe. The elastic modulus distribution along the HIFU axis is calculated from the LSW group velocity, and the process is repeated for other HIFU axis directions to obtain a 2-D distribution. In the second method, a series of cylindrically shaped HIFU pushes steered laterally generate the SWs, and their arrival time is measured along the central imaging ray line. Both strategies were tested ex vivo in tissue-mimicking gels and in vitro with resected human prostatectomy samples, demonstrating agreement across homogenous and heterogenous targets.