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A New Method for Defining the Conformity of Treatment Plan Based On Similarity Measurement

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J Duan

Shandong Cancer Hospital Affiliated to Shandong University, Jinan, Shandong province


SU-I-GPD-T-370 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Conformity is commonly evaluated the plan quality of treatment plan. The traditional calculation method of conformity index is based on the overlap volume between the target and the prescription dose area. However, the method ignores the factor that differences between target boundary lines and prescription dose lines in every CT plane. In this study, we present a new method for defining the conformity index based on similarity measurement in two-dimensional space.

Methods: One cervical cancer patient treated with IMRT plans were enrolled in this study. First, we extracted the structures of the target boundary lines and the prescription dose lines from the CT image using Computational Environment for Radiotherapy Research (CERR) software. Then, canny edge detect operator was applied to detect the contour’s edge. Finally, we evaluated the shape similarity about the target boundary lines and the prescription dose lines for every plane. The value of similarity index ranges from 0 to 1, where 1 indicates perfect overlap (identical structures).

Results: The values of similarity index for every plane was ranging from 0.8227 to 0.9598. The median value was 0.9099, the mean value is 0.8987 and the standard deviation was 0.0302. The similarity index value of several planes were less than desirable though the traditional conformity index value were acceptable.

Conclusion: The new method provides some extra information in evaluating the quality of treatment plan from two dimension planes. It may provide a supplement for traditional conformity index in quantitatively evaluating the quality of treatment plan.

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