Real-Time Dosimetry for Prostate Brachytherapy Using TRUS and Fluoroscopy

A means of achieving real-time dosimetry for prostate brachytherapy using transrectal ultrasound (TRUS) and fluoroscopy has been developed. The approach is designed to fit into the current protocol used at the Vancouver Cancer Center (VCC) for prostate brachytherapy. The TRUS and fluoroscopic images are fused using a single fluoroscopic image of the TRUS probe. The tip of each needle, used to implant the seeds, is identified in TRUS images. Using the needle tip location and the known entry point of the needle in the needle guide, a needle path is interpolated. The coronal plane coordinates of the seeds are determined from fluoroscopic images acquired at a fixed angle. The remaining coordinates of the seeds are determined from interpolated needle paths. Intraoperative seed motion is tracked using fluoroscopic images and TRUS. The dose distribution is computed and displayed in the TRUS image frame after each fluoroscopic image is acquired. Our approach is validated on a phantom and compared to the seed distributions found in computed tomography (CT) images acquired three to four hours after the procedure.