Clinical evaluation of deep learning and atlas‐based auto‐segmentation for critical organs at risk in radiation therapy

INTRODUCTION: Contouring organs at risk (OARs) is a time‐intensive task that is a critical part of radiation therapy. Atlas‐based automatic segmentation has shown some success at reducing this time burden on practitioners; however, this method often requires significant manual editing to reach a clinically accurate standard. Deep learning (DL) auto‐segmentation has recently emerged as a promising solution. This study compares the accuracy of DL and atlas‐based auto‐segmentation in relation to clinical ‘gold standard’ reference contours. METHODS: Ninety CT datasets (30 head and neck, 30 thoracic, 30 pelvic) were automatically contoured using both atlas and DL segmentation techniques. Sixteen critical OARs were then quantitatively measured for accuracy using the Dice similarity coefficient (DSC) and Hausdorff distance (HD). Qualitative analysis was performed to visually classify the accuracy of each structure into one of four explicitly defined categories. Additionally, the time to edit atlas and DL contours to a clinically acceptable level was recorded for a subset of 9 OARs. RESULTS: Of the 16 OARs analysed, DL delivered statistically significant improvements over atlas segmentation in 13 OARs measured with DSC, 12 OARs measured with HD, and 12 OARs measured qualitatively. The mean editing time for the subset of DL contours was 50%, 23% and 61% faster (all P < 0.05) than that of atlas segmentation for the head and neck, thorax, and pelvis respectively. CONCLUSIONS: Deep learning segmentation comprehensively outperformed atlas‐based contouring for the majority of evaluated OARs. Improvements were observed in geometric accuracy and visual acceptability, while editing time was reduced leading to increased workflow efficiency.