Evaluating the Effectiveness of Deep Learning Contouring across Multiple Radiotherapy Centres

Background and purpose: Deep learning contouring (DLC) has the potential to decrease contouring time and variability of organ contours. This work evaluates the effectiveness of DLC for prostate and head and neck across four radiotherapy centres using a commercial system.Materials and methods: Computed tomography scans of 123 prostate and 310 head and neck patients were evaluated. Besides one head and neck model, generic DLC models were used. Contouring time using centres' existing clinical methods and contour editing time after DLC were compared. Timing was evaluated using paired and non-paired studies. Commercial software or in-house scripts assessed dice similarity coefficient (DSC) and distance to agreement (DTA). One centre assessed head and neck inter-observer variability.Results: The mean contouring time saved for prostate structures using DLC compared to the existing clinical method was 5.9 +/- 3.5 min. The best agreement was shown for the femoral heads (median DSC 0.92 +/- 0.03, median DTA 1.5 +/- 0.3 mm) and the worst for the rectum (median DSC 0.68 +/- 0.04, median DTA 4.6 +/- 0.6 mm). The mean contouring time saved for head and neck structures using DLC was 16.2 +/- 8.6 min. For one centre there was no DLC time-saving compared to an atlas-based method. DLC contours reduced inter-observer vari-ability compared to manual contours for the brainstem, left parotid gland and left submandibular gland.Conclusions: Generic prostate and head and neck DLC models can provide time-savings which can be assessed with paired or non-paired studies to integrate with clinical workload. Reducing inter-observer variability po-tential has been shown.