Visible To Near Infra Red Hyperspectral Imaging: Visualizing The Neurological And Biological Nature Of Ischemic Tissue

Abstract

Diabetic Neuropathy is a neuropathic disorder which is associated with Diabetes Mellitus. It is known to result in lower limb ulcers which can lead to amputation. Nerve damage, microvascular dysfunctions and use of ill fitting shoes are significant causes for it. These abnormal dysfunctions can lead to Ischemia. We have used the Multimodal Hyperspectral Imaging System image areas of high pressure on the skin that correspond to pain and also to visualize vascular changes that are associated with this pain. The instrument majorly consists of near-infrared and visible charge coupled devices (CCDs), lenses, liquid crystal tunable filters (LCTFs) for both the CCDs attached to their respective lenses, and a broad band light source. Twenty healthy human subjects had their foot imaged. First, the baseline measure was taken and then an occlusion was introduced with wearing tight shoes to induce temporary Ischemia and removing the shoe resulted in Reactive Hyperemia. After removing the tight shoe the measure of hemoglobin oxygen and carbon dioxide saturation in the area reported as feeling uncomfortable was significantly different from the measure taken from the same area before the tight shoes were worn (Pval < 0.0001).Chemometric analysis produces a gray scale encoded image for the percentage of oxyhemoglobin and carboxyhemoglobin at each pixel within the field of view. Once the shoe is removed, in the microvasculature there will be an increase in the hemoglobin oxygenation saturation and a decrease in the carboxyhemoglobin and a increase of oxyhemoglobin in the macrovasculature of the skin. This study establishes that reactive hyperemia occurs 3-4 minutes after removing the tight shoe and shows that Multimodal Reflectance Hyperspectral Imaging System is a robust imaging method for monitoring vascular changes in the diabetic foot.