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 ½ ). The difference in the fluorescence intensity between 10 seconds after the rising point and baseline (PDE 10 ) was compared with the transcutaneous oxygen pressure (tcPO 2 ) at the same site ( n = 51). Results Median T ½ was 23 seconds in FII, 41 seconds in FIII ( P 10 correlated moderately with tcpO 2 ( r 2 = 0.5). A cut-off value (PDE 10 = 28) predicted a critically ischemic limb (FIII and FIV), defined as tcpO 2 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.