SU‐E‐J‐169: Process for QA of Normal Tissue Delineation and Reported Doses in Clinical Trials

Abstract

Purpose:To create and evaluate a process of using auto‐segmentation for quality assurance of doses reported to normal structures in clinical trials.Methods:Multiple atlases for normal tissue segmentation were created for the esophagus, trachea/large bronchus, and brachial plexus. These atlases were used to independently delineate 21 patients who were enrolled in a phase III study of accelerated hypofractionated IGRT for patients with stage II‐III NSCLC. The results of the multi‐atlas segmentation were visually evaluated for acceptability. The dose volume limits and the maximum point doses specified by the protocol were compared for the originally delineated and auto‐segmented contours. It was noted whether these differences affected whether plans met or failed the protocol constraints.Results:On visual inspection, the auto‐segmented contour was acceptable with the exception of 8 cases (38%) of the esophagus. In these cases, the anatomy of the esophagus was notably different from that of atlases so that the autosegmentation failed. On the other hand, the process using auto‐segmentation identified two cases where not all contours of the structure had been delineated in the original plan (one trachea/large bronchus case and one brachial plexus case). The average difference in maximum dose to the esophagus, trachea, and brachial plexus were 0.2±4.4Gy (range: – 13.6:4.7Gy), 0.2±1.1Gy (−3.9:0.8Gy), and 3.6±10.7Gy (−1.2:34.1Gy), respectively. In one esophagus case and one trachea case, the plan became unacceptable when calculated using the auto‐segmented contour, but in both cases the dosimetric difference was very small.Conclusion:Two cases (10%) of contouring with insufficient coverage (trachea/large bronchus and brachial plexus) in the original plan were identified using the proposed process. However, patient‐to‐patient variations in the position of the esophagus meant that our current auto‐segmentation is inadequate to evaluate this organ, and more work is needed to optimize the process.Work funded by Cancer Prevention Research Institute of Texas (CPRIT)