a, AUC curve for the independent data test set with n = 1,139 cases using a two-sided permutation test with 10,000 random resamplings of the data. b, For each detection that was a ‘hit’ (overlapped with a labeled malignancy), this plot shows the volume of the intersection between the detection and the ground truth divided by the volume of the union of the ground truth and the detection. In 3D, intersection over union (IOU) drops much faster than in two dimensions (2D). For example, given a 1-mm3 nodule and a correctly centered 2-mm3 bounding box, the resulting IOU will be 0.125. In 2D, a similar situation would result in an IOU of 0.25.