S2187
Physics - Inter-fraction motion management and daily adaptive radiotherapy
ESTRO 2026
IRCCS Regina Elena National Cancer Institute, Rome, Italy
Purpose/Objective: The aim of this work is to validate a new system for adaptive radiotherapy to streamline patient workflow when the need for re-planning due to anatomical changes has to be assessed. Material/Methods: We have used the new Mozi TPS (Manteia Technologies Co., Ltd) treatment planning system in its capability of generating synthetic CTs from CBCTs for adaptive planning. Ten head and neck patients and ten lung patients whose anatomical changes demanded re-planning have been selected for this retrospective study. Treatments have taken place in a Varian environment using Eclipse for planning and TrueBeam for daily imaging and delivery.For each patient the CBCT closest in time to the day of acquisistion of the new planning CT (pCTnew) has been used for the generation of the corresponding RegGAN based syntetic CT (sCT) in the ART Assistant module of the Mozi TPS (1). When available, CBCTs acquired with two different image qualities were both used to assess potential differences in sCt generation. The sCT images have then followed our standard clinical workflow. They were therefore first fed to MIM Maestro™ with Contour ProtegeAI for automatic delineation of the critical structures, then transferred to Eclipse for manual delineation of the target structures by a radiation oncologist and for plan optimization. The results were compared to what had been obtained in the same workflow with the pCTnew in terms of difference in HU values, differences in contours, differences in the DVH values of clinically relevant structures at the dose checkpoints of our clinical goals and passing rate in the gamma comparison (2%/2mm) of the dose distributions. Results: Figures 1 and 2 show the HU comparisons using the MIM analysis software for a head and neck and a lung patient, respectively. DVH differences at the clinical goal checkpoints were never found to alter clinical viability of the plans. Gamma passing rates were always above 90%
Figure 2 Conclusion:
The new system has been found to allow a faster and more effective management of the workflow in off-line adaptive radiotherapy potentially reducing imaging dose, sub-optimal treatment dose and treatment time prolongation for patients in need of re-planning. Further analysis may assess its performance in on-line procedures as well. References: (1) Li, Z., Zhang, Q., Li, H. et al.Using RegGAN to generate synthetic CT images from CBCT images acquired with different linear accelerators. BMC Cancer23, 828 (2023). Keywords: adaptive radiotherapy, CBCT-based synthetic CT Dosimetric evaluation of advanced CBCT-based online adaptive radiotherapy for the treatment of cervical cancer Jasmine Penney 1 , Krista Chytyk-Praznik 2,3 1 Physics and Atmospheric Science, Dalhousie University, Halifax, Canada. 2 Radiation Oncology, Dalhousie University, Halifax, Canada. 3 Medical Physics, QEII Cancer Center, Nova Scotia Health, Halifax, Canada Digital Poster 4514
Purpose/Objective: Cervical cancer is commonly treated with a
combination of external beam radiation therapy (EBRT) and brachytherapy. A planning CT simulation dataset is used to create the EBRT treatment plan, with a pre-treatment cone-beam CT (CBCT) scan to ensure correct patient position. Throughout the course of treatment, the tumour tends to shrink and change position due to variations in bladder and rectum filling, resulting in inadequate target coverage. [1] The oART system used in our clinic employs artificial intelligence to plan adaptive treatment fractions based on the patient’s anatomy-of-the-day CBCT scan. A new high-performance CBCT built into the oART system has a larger imaging panel and faster
Figure 1
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