Pilot Study to Determine Percent Tissue Perfusion and Cellular Viability Using SPY Imaging

Peripheral arterial disease (PAD), like other more central macrovascular diseases, is common in diabetes. PAD can lead to critical limb ischemia, either alone or when combined with an injury like a foot ulcer. The diabetic foot ulceration requires adequate circulation to heal; if the circulation is impaired such that the tissue oxygen demand exceeds supply, critical limb ischemia ensues, placing the limb at risk.

Most often, patients with critical limb ischemia, undergo multiple debridements in the operating room as well as vascular procedures, prior to reaching a viable level of amputation. This increases the patients' co-morbidities from repetitive exposure to anesthesia. Each debridement may be removing viable tissue and decreasing the length of the eventual amputation. Additionally, intraoperatively, the viability of the skin edges is a subjective assessment based on the surgeon's experience. That judgement can be inaccurate in 10-20% of cases and lad to reoperation. With the use of the SPY imaging system, a better assessment of not only macrovascularity, but also microvascularity of the tissues is able to be evaluated objectively. This helps identify the tissues that are underperfused.

The investigators are unaware of any literature evaluating the use of SPY imaging in the lower extremities intraoperatively during amputations or debridements. There are many studies published for the use of this technology during ophthalmic procedures , cerebral aneurismal repair, cardiac surgery and breast reconstruction. In cardiac surgery, the use of ICG based imaging has proven to be helpful in assessing the quality of bypass grafts and eliminating the need for radiography or catheter insertion (Reuthebuch et al., 2004). In ophthalmic procedures, ICG angiography has been fundamental in identifying many microvascular pathologies (Slakter, Yannuzzi, Guyer, Sorenson, \& Orlock, 1995). Furthermore, neurosurgeons have found that the use of ICG angiography is far more superior than DS angiography in identifying small vessels . As it has already been proven to be a good adjunct intraoperatively to visualize microvasculature, the investigators would like to apply this to the lower extremities. Identifying underperfused tissues intraoperatively can help the surgeon objectively decide an appropriate level of amputation/debridement to effectively minimize the number of revisional surgeries. Also, there are no studies that comprehensively evaluate and compare the effectiveness of other modalities that also attempt to assess vascularity with the SPY imaging system. The information gained could be pivotal and help to gain more insight in patients with difficult to heal wounds, especially in the presence of PVD.