Purpose/Objective(s): Adaptive radiotherapy has been introduced to reduce normal tissue toxicities and escalate tumor dose and is evaluated in clinical trials. The purpose of our study is to evaluate the feasibility and efficacy of deformable registration, as compared with rigid registration, for adaptive planning of RTOG 1106 Randomized Phase II Trial of Individualized Adaptive Radiotherapy Using During-Treatment FDG-PET/CT and Modern Technology in Locally Advanced Non-Small Cell Lung Cancer (NSCLC). Purpose/Objective(s): Thirteen patients from RTOG 1106 trial with both primary planning CTs and re-scanned CTs were included in this study. An experienced radiation oncologist contoured the tumor volumes (TVs) and organs at risk (OARs) on the re-scanned CTs, and treatment plans were made on these CTs. Backward deformable registration (from adaptive image to initial image) and Forward deformable registration (from initial images to adaptive images) were performed upon these patients. The deformed contours were compared with the original contours for geometry and dosimetry. The geometry comparison was performed using the Dice Similarity Coefficient (DSC) and Mean Distance to Agreement (MDA). The dosimetry differences were evaluated by the deviation of dose between deformed contours and original. Five different contours were studied that included Heart, Lungs-GTV, Esophagus, Spinal Cord, and PTV. The performance of backward deformable registration and forward deformable registration were also compared. Results: The average DSC of all contours for forward deformable registration is 84.83±15.48%, while the average DSC for backward deformable registration is 85.12±16.01%. The DSC for Heart, Lung-L, Lung-R, and GTV are 86.69±5.70%, 95.17±2.06%, 96.17±1.83%, and 61.88±13.24% respectively. The relatively low DSC value for GTV is due to the volume change of GTVs from the primary CTs to the re-scanned CTs. The MDA for Esophagus and Spinal Cord are 1.89±0.56mm and 2.19±1.59mm respectively. For the dosimetric comparison, the average deviation of V30Gy, V40Gy, Dmax, and Dmean of Heart, V5, V20, and Dmean of Lungs, Dmax and Dmean of Esophagus, Dmax of Spinal Cord, and Dmin, Dmax, and D95 of PTV are 7.08±7.97%, 5.86±6.95%, 1.38±2.65Gy, 3.46±4.35Gy, 1.45±1.20%, 0.95±0.76%, 0.55±0.46Gy, 0.62±0.53Gy, 3.22±2.93Gy, 0.72±0.73Gy, 10.39±11.13Gy, 0.59±1.15Gy, 4.30±5.90Gy Respectively. Conclusion: Deformable registration is highly desirable for accurate dosimetry of adaptive planning. Detailed workflow of the implementation needs to be optimized.
Zhong, H., Guttmann, D. M., Huang, M., Geng, H., Cheng, C., Kong, F. M., … Xiao, Y. (2017). Evaluating the Feasibility of Applying Deformable Registration Into Adaptive Therapy for NRG Oncology RTOG 1106. International Journal of Radiation Oncology*Biology*Physics, 99(2), E509–E510. https://doi.org/10.1016/j.ijrobp.2017.06.1822