Comparative Analysis of Respiratory Monitoring Systems in Radiotherapy: Benchmarking RPM4D and DL4D Using a Novel Mobile Phantom

Respiratory monitoring systems are equipped with additional hardware such as cameras. However, one of the most developments is equipment for deviceless computed tomography (CT), that can monitor the patient’s respiratory phases and produce four-dimensional (4D) images without additional equipment. We investigated the determination of changes in target volume and critical structures in 4D images obtained with additional hardware (Real-Time Positioning Management System, RPM4D) and without additional hardware (Deviceless System, DL4D) from the CT. We evaluated their contribution to clinical use. Material and Methods: A mobile phantom was designed. Imaging was performed in the phantom under the same set-up conditions on both systems. The geometric discrepancy of gross tumour volume (GTV) and organs at risk(OAR) between RPM4D and DL4D images were evaluated. The assessment was based on the Dice similarity coefficient (DSC) and center of mass shift (COM) using both scanning protocols. The DSC for the right lung was 0.98, left lung 0.99, and tumour volume 0.92. Left and right lung displacement was up to 0.07 cm. It can be concluded thespatial overlaps were similar for both systems.