Near infra-red imaging of the microvasculature in comparison with resin casting of amputated limbs

Part one, proof of concept: Two amputated lower limbs will be imaged with a near-infra red (NIR) camera and indocyanine green dye contrast. The imaging will involve recording the peak intensity of the fluorescence of the dye, and the time taken to peak intensity. Bright spots will be indicated and marked on the limb. After imaging, the limb will undergo resin casting, whereby resin will be injected into veins of the limb and allowed to set. This will produce a map of the micro venous system, with markers where imaging showed potential areas of reflux. The resulting resin map will be analysed to determine the degree of venous reflux in multiple regions of interest in the limb. This will be correlated with the data obtained from the NIR imaging. Part Two: Continuation If part one provides usable data from both imaging and resin casting, participants will be asked if they would like to undergo imaging prior to amputation, to allow for better correlation. The imaging session will take less than one hour, and involves cannulating the participant for a local injection of indocyanine green (ICG) dye. of ICG solution (0.02 mg/ml) will be injected into a vein in the foot or at the level of the ankle, for the duration of the imaging sequence . This may be possible in neuropathic patients, who do not feel pain in their limbs. Patients will only be included in this extra imaging if a vascular surgeon who is not part of the study deems it appropriate. We aim to have three more participants, and hope to have at least one who is able to undergo imaging prior to amputation.