Toward in vivo Dosimetry for Prostate Radiotherapy With a Transperineal Ultrasound Array: A Simulation Study

X-ray-induced acoustic computed tomography (XACT) is a promising imaging modality to monitor the position of the radiation beam and the deposited dose during external beam radiotherapy delivery. The purpose of this study was to investigate the feasibility of using a transperineal ultrasound (TPUS) transducer array for XACT imaging to guide the prostate radiotherapy. A customized 2-D matrix ultrasound transducer array with 10000 ( 100×100 elements) ultrasonic sensors with a central frequency of 1 MHz was designed on a 5 cm ×5 cm plane to optimize 3-D volumetric imaging. The CT scan and dose treatment plan for a prostate patient undergoing intensity-modulated radiation therapy (IMRT) were obtained. The in-house simulation was developed to model the time varying X-ray induced acoustic (XA) signals detected by the TPUS array. A 3-D filtered back projection (FBP) algorithm has been used for 3-D XACT image reconstruction. The results of this study will greatly enhance the potential of XACT imaging for real-time in vivo dosimetry during radiotherapy.