Quality assurance for the clinical implementation of kilovoltage intrafraction monitoring for prostate cancer VMAT

Purpose: Kilovoltage intrafraction monitoring (KIM) is a real‐time 3D tumor monitoring system for cancer radiotherapy. KIM uses the commonly available gantry‐mounted x‐ray imager as input, making this method potentially more widely available than dedicated real‐time 3D tumor monitoring systems. KIM is being piloted in a clinical trial for prostate cancer patients treated with VMAT (NCT01742403). The purpose of this work was to develop clinical process and quality assurance (QA) practices for the clinical implementation of KIM. Methods: Informed by and adapting existing guideline documents from other real‐time monitoring systems, KIM‐specific QA practices were developed. The following five KIM‐specific QA tests were included: (1) static localization accuracy, (2) dynamic localization accuracy, (3) treatment interruption accuracy, (4) latency measurement, and (5) clinical conditions accuracy. Tests (1)–(4) were performed using KIM to measure static and representative patient‐derived prostate motion trajectories using a 3D programmable motion stage supporting an anthropomorphic phantom with implanted gold markers to represent the clinical treatment scenario. The threshold for system tolerable latency is