Qualitative nerve segmentation results. Qualitative nerve segmentation results under different image conditions (picture distance and brightness), with summary statistics and example images from all 5 cross-validation test folds. For each of the six image conditions labeled at the top of the figure, we show three results: a plot at the top with the mean DSC scores and 95% confidence intervals (as shown in Table 1), and in the two bottom boxes, corresponding example good (green) and worse (orange) results from each image condition to illustrate the range of model performance. For each vertical image pair in the two bottom boxes, the original image is on top and the overlaid predicted and ground-truth segmentations annotated by surgeons is on the bottom. In the overlaid segmentations, the intersection of the predicted and ground-truth segmentations (true positive) is green, false positive pixels are in yellow, and false negative pixels are in blue. Note that both far-away and close-up images and corresponding segmentations are shown post-crop with the cropping model for better segmentation visualization. In the good segmentation cases, the predicted segmentation masks track closely with the ground-truth and demonstrate successful learning of expected nerve morphology. Furthermore, notice that the algorithm performs well even in difficult scenarios such as very thin nerves (e.g. far-away, bright lighting), small nerves (far-away, medium lighting), and boundary details (close-up, dim lighting; close-up, medium lighting). The worse segmentation cases highlight challenging scenarios for the model, such as missing very small nerves (far-away, bright lighting), anatomies in better-lit portions distracting from a poorly-lit nerve (far-away, dim lighting), artifacts due to neighboring tissue texture (far-away, medium lighting), difficulty with irregular nerve shapes that deviate from more common, smooth nerve morphologies in the dataset (close-up, dim lighting; close-up, medium lighting), and light reflectance on the nerve leading to over-segmentation (close-up, bright lighting). The worse cases occur more frequently and severely in poorer distance and lighting conditions. These cases illustrate that capturing higher-quality images with respect to both picture distance and brightness is important for achieving better segmentation performance. Best viewed in color.