Prostate cancer radiotherapy using real-time x-ray monitoring (KIM) of tumour during treatment.

Intervention name: Kilovoltage Intrafraction Monitoring (KIM) for real-time motion management Description: The investigational intervention is the use of the KIM software technology to continuously monitor prostate position during external beam radiotherapy, and to trigger corrective actions when motion exceeds protocol thresholds. The KIM software receives a feed of kV image frames for the target and fiducial markers, auto-segments the markers and outputs the 3D position of the target in real-time relative to where the target should be. It flags to the treatment staff if there needs to be an image guided shift. Procedures (how the device is used as part of treatment): · Patients receive standard-of-care external beam radiotherapy for prostate cancer (fractionation per clinician). · In addition, the linac’s kV x-ray fluoroscopic function is turned on during treatment. The imaging frames are received and processed by the KIM workstation. The software tracks three intraprostatic fiducial markers in real-time and provides a visual output to the qualified radiation therapists responsible for treating the patient. · If prostate motion of magnitude equal to or greater than 3 mm persists for a period of five seconds or longer, KIM signals radiation therapists to: - pause the treatment beam (gating), and - apply couch shifts to return the prostate to the planned position before resuming treatment. · The intervention therefore consists of real-time monitoring, beam gating, and intra-fraction patient repositioning directed by KIM. · If KIM is not available or fails, treatment proceeds with the site’s standard image-guidance method (SOC comparator). Mode of delivery: Individualised, real-time software-guided monitoring and correction during treatment beam-on time. Number/timing of sessions: KIM is applied at every radiotherapy fraction across the patient’s prescribed course (5 fractions for SABR or more for conventional regimens). Who delivers the intervention: Radiation therapists trained and credentialed in KIM, with a trial physicist on-site for quality assurance and technical guidance. Duration/intensity: Monitoring is continuous throughout beam delivery (approx. 15–25 minutes per fraction), at 5–10 Hz sampling. Location: Radiotherapy departments at 10 Australian sites. Adherence/fidelity: KIM logs and Mosaiq/ARIA treatment records will document whether monitoring and gating were active and whether corrective shifts were performed. Physicist on-site will document via Mosaiq notes/CRF on diversions from protocols. Detailed workflow instructions, QA and commissioning documents have been developed by the trial’s clinical team. Central trial monitoring will confirm protocol compliance. AI sub-study: The technical data from the PRIME cohort (kV frames, position logs, plan and structure set files) will be used to train and validate published AI-based maker and marker-less models developed by ImageX (Mylonas, A., Li, Z., Mueller, M. et al. Patient-specific prostate segmentation in kilovoltage images for radiation therapy intrafraction monitoring via deep learning. Commun Med 5, 212 (2025). https://doi.org/10.1038/s43856-025-00935-2). No treatment intervention will be made using these models. The imaging frames will be used for validation of model, workflow development, comparison and benchmarking against the KIM template-based ground truth used in PRIME.