Tianjin Medical University Cancer Institute and Hospital Tianjin, Tianjin
W. Wang1, W. Sun2, D. Zhang3, Z. Zhu3, M. Li3, J. Zhang3, and Y. Tan4; 1Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, Tianjin, China, 2Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin; Tianjin, Chi, Tianjin, Tianjin, China, 3Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin; Tianjin, Chi, Tiajin, Tianjin, China, 4Suzhou Puneng Medical Technology Co.,Ltd, Suzhou, Jiangsu, China
Purpose/Objective(s): To explore image-guided location of tumor bed and real-time three-dimensional dose assessment in intraoperative radiotherapy techniques. Materials/
Methods: The low-energy X-ray intraoperative radiation therapy (IORT) was equipped with a set of flat applicators with the sizes including 1 cm, 2 cm, 3 cm, 4 cm, 5 cm and 6 cm. The same sized applicator positioning rings were used to locate the tumor bed and fix the applicators. The original positioning rings were made of metal. In order to avoid artifacts, 3D printing technology was used to produce non-metallic positioning ring. The positioning ring was made of Polylactic Acid (PLA) 3D printing material with good biocompatibility. Moreover, it was fully matched to the shape and size of each applicator, and had specific markers. During the operation, an appropriately sized positioning ring was sutured to the tumor bed to be irradiated. The intestine and other surrounding normal tissues were pushed away from the irradiation area determined by the positioning ring. Then the dose concerned points such as cut edges and intestinal wall were marked with titanium clips under direct visualization. A 3D mobile C-arm imaging device was used to acquire Cone beam CT (CBCT) images of the tumor bed, which were then transferred to a self-developed IORT treatment planning system (Puneng Medical Technology Co.,Ltd, IORT TPS) for dose calculation and evaluation. The main functions of the IORT TPS included automatic recognition of positioning rings and points of interest (POIs) marked by titanium clips, applicators reconstruction, prescription dose setting, dose distribution evaluation and planning optimization. After importing CBCT images into IORT TPS, the positioning ring and POIs will be recognized. Finaly, the absolute and statistical values of the dose distribution for the whole irradiated area and POIs can be obtained in real time, which will be used by the doctor to adjust the final prescribed dose after evaluation. Results: For the first time, our study realized real-time display of 3D tumor bed and dose distribution in low-energy X-ray IORT, based on a mobile CBCT device and non-metallic flat applicators positioning ring, and independently developed IORT TPS. With the assistance of a mobile 3D C-arm device and non-metallic positioning rings, the CBCT of the tumor bed can be visualized. Moreover, titanium clips were acquired to mark the surrounding POIs before they can be recognized. Conclusion: Through three-dimensional dose evaluation, the overall dose of the tumor bed and the adjacent OAR can be more accurately assessed. It can more effectively improve local tumor control while maximizing the protection of normal tissues. This approach could be applied to irradiation of pancreatic cancer, rectal cancer and other tumor beds suitable for flat applicators, and provided possibilities of further clinical research for achieving quantifiable three-dimensional dose in intraoperative radiotherapy.
