An Approach for Evaluation of Delineation Accuracy of GTV Contours with Considering Interobserver Variability in Reference Contours : Impact of MAR on Radiation Treatment Planning

Abstract

We have proposed an approach to evaluate delineation accuracy of gross tumor volume (GTV) contours with considering interobserver variability in reference contours with Dice's similarity coefficient (DSC) and Hausdorff distance (HD). The DSC and HD denote the degree of region similarity between a reference region and a compared region. Impacts of metal artifact reduction (MAR) technique on radiation treatment planning (RTP) including the delineation of GTV without metal artifacts contours considering the reference variability of 6 radiation oncologists in RTP have been investigated by using the proposed approach. Planning computed tomography (CT) images without and with metal artifacts were acquired by scanning an anthropomorphic skull phantom including a simulated GTV without and with putting crowns on teeth, respectively. The planning image without metal artifacts was considered a reference image. Six radiation oncologists delineated three contours of the GTV on CT images without and with MAR (w/oMAR and wMAR), and the reference image. The average DSC and HD between the reference and wMAR images were 0.62 and 4.43 mm, respectively,whereas they were 0.56 and 4.85 mm, respectively, between the reference and w/oMAR images (P < 0.05). In addition,there were no statistically significant differences between the reference and wMAR images with respect to D90 and D95,which were defined as the minimum doses delivered to 90% and 95% of planning target volumes (PTVs), respectively (P > 0.05). The proposed approach could evaluate the delineation accuracy of GTV contours with taking into account interobserver variability in reference contours by showing the impact of the MAR technique on the RTP.