Comparative Study of Pulsed Versus Continuous High‐Intensity Focused Ultrasound Ablation Using In Vitro and In Vivo Models

Objectives To compare the efficacy of pulsed high‐intensity focused ultrasound (PHIFU) versus continuous high‐intensity focused ultrasound (CHIFU) ablation at identical doses. Methods Continuous and pulsed HIFU (1200 J) at duty cycles (DCs) of 60% and 20% were examined for their capacity to ablate bovine liver tissue in vitro and rabbit liver tissue in vivo. After ablation, grayscale changes and pathologic characteristics were observed or measured, and the tissue necrosis volume, energy efficiency factor, and average grayscale density were calculated. Results The pulsed mode generated greater liquefaction necrosis. An inconspicuous grayscale change was observed for PHIFU at a DC of 20% in some samples, which appeared as an elliptical cavity. The energy efficiency factor of PHIFU at a DC of 60% was significantly lower than that of CHIFU, as observed both in vitro and in vivo (P