Thin‐Profile Transducers for Intraoperative Hemostasis

Our goal has been to develop thin‐profile HIFU applicators for intraoperative hemostasis. The HIFU device consisted of a concave PZT element encased in a spoon‐shaped aluminum housing with the diameter of 4 cm and thickness of 1 cm. The housing front surface had a thickness of $34$ ultrasound wavelength in aluminum (0.92 mm) to provide acoustic matching. The device had a resonant frequency of 6.26 MHZ, and efficiency of 42%. The ultrasound field was observed using hydrophone field mapping and radiation force balance. The full‐width half‐maximum (FWHM) dimensions of the focal region were 0.6 mm and 2.2 mm in lateral and axial direction, respectively. The maximal intensity at the focus was 9,500 W/cm² (in water). The device was tested using BSA‐polyacrylamide gel phantom and rabbit kidney in vivo. HIFU application for 10 s produced lesions in the gel phantom (lesion width of 3 mm), and rabbit kidney in vivo (lesion width of 8 mm). A thin‐profile HIFU applicator has advantages of high efficiency, simple design, and small dimensions.