Training and assessing convolutional neural network performance in automatic vascular segmentation using Ga-68 DOTATATE PET/CT

To evaluate a convolutional neural network's performance (nnU-Net) in the assessment of vascular contours, calcification and PET tracer activity using Ga-68 DOTATATE PET/CT. Patients who underwent Ga-68 DOTATATE PET/CT imaging over a 12-month period for neuroendocrine investigation were included. Manual cardiac and aortic segmentations were performed by an experienced observer. Scans were randomly allocated in ratio 64:16:20 for training, validation and testing of the nnU-Net model. PET tracer uptake and calcium scoring were compared between segmentation methods and different observers. 116 patients (53.5% female) with a median age of 64.5 years (range 23-79) were included. There were strong, positive correlations between all segmentations (mostly r > 0.98). There were no significant differences between manual and AI segmentation of SUVmean for global cardiac (mean +/- SD 0.71 +/- 0.22 vs. 0.71 +/- 0.22; mean diff 0.001 +/- 0.008, p > 0.05), ascending aorta (mean +/- SD 0.44 +/- 0.14 vs. 0.44 +/- 0.14; mean diff 0.002 +/- 0.01, p > 0.05), aortic arch (mean +/- SD 0.44 +/- 0.10 vs. 0.43 +/- 0.10; mean diff 0.008 +/- 0.16, p > 0.05) and descending aorta (mean +/- SD < 0.001; 0.58 +/- 0.12 vs. 0.57 +/- 0.12; mean diff 0.01 +/- 0.03, p > 0.05) contours. There was excellent agreement between the majority of manual and AI segmentation measures (r >= 0.80) and in all vascular contour calcium scores. Compared with the manual segmentation approach, the CNN required a significantly lower workflow time. AI segmentation of vascular contours using nnU-Net resulted in very similar measures of PET tracer uptake and vascular calcification when compared to an experienced observer and significantly reduced workflow time.