Inferences About Prostate Intrafraction Motion From Pre- and Posttreatment Volumetric Imaging

Purpose To evaluate the ability of rectal filling, bladder filling, and prostate localization from pre- and posttreatment volumetric imaging to predict prostate intrafraction motion. Methods and Materials Pre- and posttreatment cone beam computed tomography images (CBCTs) and intrafractional kV fluoroscopy were acquired at each fraction for 20 prostate patients in supine position, totaling 374 fractions available for analysis. Rectal and bladder filling status were evaluated for each CBCT, and correlation with prostate intrafraction motion measured from kV fluoroscopy was performed. The accuracy of pre and posttreatment prostate localization to predict intrafraction motion was evaluated. Results Rectal filling status was a significant predictor of prostate intrafraction motion ( p