Focal beam distortion and treatment planning in abdominal focused ultrasound surgery

The purpose of this study was to numerically demonstrate the focal-beam distortion in abdominal focused ultrasound surgery, and to present a phase correction procedure to restore the focal beam patterns. Abdominal MR data from four uterine fibroid patients were obtained to reconstruct the 3-D meshes of interfaces used in simulations, and one patient was selected to perform the analysis of key parameters in focused ultrasound surgery. Results show that, without phase correction, the focused beam can be severely distorted while using a frequency above 1 MHz or delivering ring-shape focal patterns. Different focal positions at the same depth may require a different power to induce the same ultrasonic intensity level (up to 179% among the different focal patterns). After adding a phase correction procedure, the distorted focal beams can be restored, and the peak intensity can be largely recovered (up to 85% among the different focal patterns). This study may offer important implications and information for treatment planning toward optimizing focused ultrasound surgery in uterine fibroid or other abdominal tumor treatments.