A multi‐element high intensity focused ultrasound transducer: Design, fabrication, and testing Free

The goal of this project is to develop an intra‐cavity image‐guided high intensity focused ultrasound (HIFU) device using piezocomposite technology and commercially available ultrasound imaging. The HIFU array, manufactured by Imasonic Corporation, is an 11‐element annular phased array, with a focal length range of 30–60 mm, and operating frequency of 3 MHz (bandwidth of 1 MHz). The imaging probe (C9‐5, Philips) is configured such that the focal axis of the HIFU beam was within the image plane. The array includes six complete central rings and five side‐truncated peripheral rings, all with the natural radius of curvature of 50 mm. Impedance of all elements is approximately 50 ohms (10% accuracy for real and imaginary parts). Cross coupling between adjacent elements is less than, −40 dB. High power measurements showed more than 75% efficiency, at surface intensity of 2.66 W/cm². Schlieren imaging showed effective focusing at all focal lengths (30–60 mm). The image‐guided HIFU device requires water or hydrogel coupling, and possibly water cooling. The results of the full characterization for lesion formation in tissue‐mimicking phantoms and biological tissues will be presented. Possible applications include uterine fibroids, abnormal uterine bleeding, and intraoperative hemostasis of occult hemorrhage.