Development of dedicated phantom for end-to-end testing of multiple image-guidance configurations incorporating light-section-based surface guidance system

Purpose: Radiotherapy devices with multiple image-guidance systems, such as surface-guided radiation therapy (SGRT), have been widely used in recent years. However, in the case of SGRT devices using the light-section method, coordinate coincidence evaluation using a phantom for SGRT devices with patterned light projection is not appropriate. Hence, this study aims to develop a dedicated phantom able to evaluate both the detection accuracy and coordinate coincidence of multiple IGRT configurations, including light-section-based SGRT devices. Materials and method: First, we developed an end-to-end (E2E) phantom that can be scanned by CT and detected by a light-section-method-based SGRT device. Second, the detection accuracy of the phantom under three reference data acquisition conditions was evaluated using the E2E phantom. The three conditions were a body surface image detected by VOXELAN in the simulation CT room, a body surface image reconstructed from the volume data of the simulation CT room, and a body surface image acquired by VOXELAN in the radiotherapy room. Finally, the coordinate coincidence of the image-guidance system was evaluated using the E2E phantom. Result: Upon comparing detection accuracy among the three reference data acquisition methods, we found that the reference data generated in the CT room had the largest error (0.58 mm at maximum). The coordinate coincidences of the multiple image-guidance systems were within 1 mm for all components after the maintenance of VOXELAN using E2E phantom. Furthermore, the long-term direction stability was worse in the longitudinal direction. Conclusion: The new E2E phantom can be used to evaluate the detection accuracy of a light-section-based SGRT system and the coordinate coincidence using a Winston–Lutz-based method in multiple image-guided configurations. The detection accuracy in the three different reference images of VOXELAN using this phantom improved to within 1 mm in all directions.