Evaluation of Delivery Analysis to Detect Intrafractional Motion during Tomotherapy

The purpose of this study was to investigate the ability of a management system (Delivery Analysis: DA) to detect intrafractional motion during intensity-modulated radiation therapy (IMRT) in tomotherapy mode. Tomotherapy has made it possible to manage internal movements during treatment using software DA, which quantifies using the information of the passing dose obtained during the radiation treatment of patients. First, three treatment plans for the test were created (lumbar spine, prostate, and femur). Second, a pelvis phantom was moved in the X, Y, and Z directions, and a sinogram was acquired. The magnitudes of the movements were 3 mm, 5 mm, and 10 mm, respectively. Finally, the ability of DA to detect the motion was evaluated by comparing the sinogram obtained by moving the phantom with a reference sinogram obtained without movement. The sensitivity of DA could be detected with a shift amount of 3 mm (gamma analysis tolerance 0.3 mm/0.3%). The average gamma analysis of each direction at 0.3 mm/0.3% tolerance at each treatment site was 96.1% for the prostate, 93.5% for the lumbar spine, and 94.4% for the femur. Additionally, the average gamma pass rate results for the pelvic phantom in the X, Y, Z directions for a 10 mm shift were 96.2%, 96.3%, and 95.9%, respectively. DA is a powerful tool with high detection sensitivity and ability to detect body movement during treatment.