Evaluation of a commercial DIR platform for contour propagation in prostate cancer patients treated with IMRT/VMAT

Abstract

Purpose: To assess the performance and limitations of contour propagation with three commercial deformable image registration (DIR) algorithms using fractional scans of CT-on-rails (CTOR) and Cone Beam CT (CBCT) in image guided prostate therapy patients treated with IMRT/VMAT. Methods: Twenty prostate cancer patients treated with IMRT/VMAT were selected for analysis. A total of 453 fractions across those patients were analyzed. Image data were imported into MIM (MIM Software, Inc., Cleveland, OH) and three DIR algorithms (DIR Profile, normalized intensity-based (NIB) and shadowed NIB DIR algorithms) were applied to deformably register each fraction with the planning CT. Manually drawn contours of bladder and rectum were utilized for comparison against the DIR propagated contours in each fraction. Four metrics were utilized in the evaluation of contour similarity, the Hausdorff Distance (HD), Mean Distance to Agreement (MDA), Dice Similarity Coefficient (DSC), and Jaccard indices. A subfactor analysis was performed per modality (CTOR vs. CBCT) and time (fraction). Point estimates and 95% confidence intervals were assessed via a Linear Mixed Effect model for the contour similarity metrics.Results: No statistically significant differences were observed between the DIR Profile and NIB algorithms. However, statistically significant differences were observed between the shadowed NIB and NIB algorithms for some of the DIR evaluation metrics. The Hausdorff Distance calculation showed the NIB propagated contours vs. shadowed NIB propagated contours against the manual contours were 14.82 mm vs. 8.34 mm for bladder and 15.87 mm vs. 11 mm for rectum, respectively. Similarly, the Mean Distance to Agreement calculation comparing the NIB propagated contours vs. shadowed NIB propagated contours against the manual contours were 2.43 mm vs. 0.98 mm for bladder and 2.57 mm vs. 1.00 mm for rectum, respectively. The Dice Similarity Coefficients comparing the NIB propagated contours and shadowed NIB propagated contours against the manual contours were 0.844 against 0.936 for bladder and 0.772 against 0.907 for rectum, respectively.The Jaccard indices comparing the NIB propagated contours and shadowed NIB

Review and recommendations on deformable image registration uncertainties for radiotherapy applications

“…The choice of the DIR algorithm and parameter settings influences the DVF obtained when registering the same image pair. Several studies investigate the performance of different DIR algorithms, for example in HN (Hardcastle et al 2012 , Močnik et al 2018 , Qin et al 2018 , Lee et al 2020 , Kubli et al 2021 ), lung (Kadoya et al 2014 , Scaggion et al 2020a ), liver (Zhang et al 2012 , Sen et al 2020 ) or pelvis (Hammers et al 2020 ). Some commercial DIR algorithms offer the possibility of parameter adjustments, such as registration metrics, guiding structures, regularisation levels, regularisation weights, or contrast level sensitivity, which causes uncertainty of the algorithm to vary (Ziegler et al 2019 ).…”