SU‐FF‐J‐48: Developing In‐Line KV Fluoroscopic Verification for 4D Adaptive Radiotherapy

Purpose: To develop a system for on‐line real‐time treatment verification for 4D‐ART using in‐line kV fluoroscopy that will be included in a new generation of accelerator. Method and Materials: We have developed a software tool, as a component of the 4D‐ART verification system, to register fluoroscopic with dynamic (time‐sequenced) DRR (DDRR) images. The fluoroscopic images are obtained using kV x‐rays in‐line with the treatment‐beam direction. The DDRR images(DRRs at different phases during respiratory cycle) are generated from 4DCT. The image registration of DDRR and fluoroscopy is based on pre‐defined structures or points of interest and needs to be performed on‐line in real time, allowing the treatment parameters to be modified in real time if a discrepancy is observed. To approve the principle, we have employed a simulator (Siemens/Mevasim) to acquire the fluoroscopic images. Both hardware and software tools were developed to synchronize the acquisition of fluoroscopy with respiratory signal using a pressuresensor (Anzai). This synchronization, in turn, harmonizes fluoroscopic images with DDRR. The verification system was tested on a motion phantom and on lung cancer cases. Results: The system developed can effectively register respiration‐synchronized fluoroscopic and DDRR images for both phantom and patient data. The registration is able to detect discrepancies between planning images (DDRR) and verification images (in‐line fluoroscopy) for a 4D‐ART delivery. The system is found to be effective for validating respiratory gating. Conclusion: We have developed a treatment verification system for 4D‐ART. The system, employing in‐line kV fluoroscopy, may be used for validating respiratory gating and for 4D‐ART with the new generation of image‐guideddelivery machine capable of in‐line dynamic imaging. The system can be also potentially useful for 4D real‐time tumor tracking based on fluoroscopy.Conflict of Interest: This work is supported in part by Siemens OCS.