Application of digital simulator in radiation field verification of intensity modulated radiation therapy

Objective To test whether the treatment volume is consistent with the target volume under digital simulator. Methods The patients were divided into head and neck, thoracic, and abdominal cancer groups, with 30 cases in each group, and the radiation fields were verified. The 0°and 90°digital reconstructed radiograph (DRR) images reconstructed by treatment planning system (TPS) was transported to digital simulator. The simulator bed was moved from reference point for positioning to isocenter point for radiotherapy. Then the 0° and 90°X ray images were collected. 2D/2D matching program was applied to accommodate the region of interest (ROI). A 10 cm×10 cm area in the radiotherapy field was set as the ROI, and the 0° and 90° DRR images matched with the corresponding X ray image automatically or manually. The bony structures of ROI in the two corresponding images were verified for consistence, and the correction error between the two images was calculated. Results The error after radiation field verification and correction error were analyzed in each group. The error was less than 3 mm on X, Y and Z axis in head and neck cancer group and less than 5 mm in thoracic and abdominal cancer group, respectively. Conclusions The digital simulator can verify the treatment volume and guarantee the accuracy during radiotherapy, which satisfy the clinical requirements. Key words: Conformal intensity modulated radiation therapy; Digital simulator; Radiation field verification; Error