A Quantitative Method for Evaluating Local Perfusion Using Indocyanine Green Fluorescence Imaging

Background: The purpose of this study is to introduce a new method, indocyanine green fluorescence imaging (ICG-FI), as an adjunct to distal pressure measurements in patients with peripheral arterial disease and symptomatic lower limb ischemia. Methods: A total of 34 patients with peripheral arterial disease, including 11 with claudication (Fontaine II), 7 with rest pain (FIII), and 16 with an ulcer or gangrene (FIV), were enrolled. After an intravenous injection of ICG (0.1 mg/kg), foot perfusion was recorded by an infrared light camera. Fluorescence intensity was plotted on a time-intensity curve using recorded images, allowing the calculation of new parameters. Severity of ischemia was assessed as the duration between the rising point and half value of maximum brightness (T-1/2). The difference in the fluorescence intensity between 10 seconds after the rising point and baseline (PDE10) was compared with the transcutaneous oxygen pressure (tcPO(2)) at the same site (n=51). Results: Median T-1/2 was 23 seconds in FII, 41 seconds in FIII (P < 0.05), and 17 seconds in FIV patients. PDE10 correlated moderately with tcpO(2) (r(2) = 0.5). A cut-off value (PDE10 = 28) predicted a critically ischemic limb (FIII and FIV), defined as tcpO(2) < 30 mm Hg with a sensitivity of 100% and specificity of 86.6%. Conclusions: Local tissue perfusion can be quantitatively evaluated by using ICG fluorescence imaging. It is a safe, fast, noncontact method of imaging, which may be useful even at the ulcer itself and in the circumferential area.