MicroCT optimisation for imaging fascicular anatomy in peripheral nerves

Vagus nerve stimulation (VNS) is a promising therapy for treatment of various conditions resistant to standard therapeutics. However, due to the lack of understanding of the fascicular organisation of the vagus nerve, VNS leads to unwanted off-target effects. Micro-computed tomography (microCT) can be used to trace fascicles from periphery and image fascicular anatomy. In this work we optimised the microCT protocol of the rat sciatic and subsequent pig vagus nerves. After differential staining, the optimal staining time was selected and scanning parameters were altered in subsequent scans. Scans were reconstructed, visualised in ImageJ and fascicles segmented with a custom algorithm in Matlab to determine ultimate parameters for tracking of the nerve. Successful segmentation for tracking of individual fascicles was achieved after 24 hours and 120 hours of staining with Lugol's solution (1% total iodine) for rat sciatic and pig vagus nerves, respectively, and the following scanning parameters: 4 m voxel size, 35 kVp energy, 114 A current, 4 W power, 0.25 fps in 4 s exposure time, 3176 projections and a molybdenum target. The optimised microCT protocol allows for segmentation and tracking of the fascicles within the nerve. This will be used to scan the full length of the pig, and possibly, the human vagus nerves. The resulting segmentation map of the functional anatomical organisation of the vagus nerve will enable selective VNS ultimately allowing for the avoidance of the off-target effects and improving its therapeutic efficacy.