Three-dimensional ultrasound-based target volume delineation and consequent dose calculation in prostate cancer patients with bilateral hip replacement: A report of 4 cases

Aim: To investigate the role of 3D ultrasound (3D-US) in target volume delineation in prostate cancer radiotherapy. Methods: Four patients with intermediate risk prostate cancer and metal artifacts on planning computed tomography (CT) due to previous bilateral hip replacement underwent 3D-US with the Clarity platorm (Clarity System, Elekta, Stockholm, Sweden) to allow for image-guided procedures. Ultrasound and CT images were coregistered to allow for better delineation of the prostate gland and organs at risk (OAR). Electron density override (EDO) and standard electron density (EDS) methods were compared for appropriate dose calculation. Results: 3D-US and planning CT minimized image artifacts, providing better evidence of patient anatomy, particularly regarding soft tissue visualization. Prostate gland and seminal vesicles were better delineated, particularly in the posterior aspect. Anterior rectal wall and bladder neck were more visible. No difference was found in terms of average planning target volume dose, D_15%, or D_25% for rectum or D_15%, D_25%, or D_35% of bladder between EDO and EDS. Conclusions: 3D-US proved to be a viable tool for target volume and OAR visualization in patients with prostate cancer with hip prostheses.