**3. ICG angiography**

Intestinal ischemia remains a devastating complication in vascular surgery, especially in surgical repair of abdominal aortic aneurysms (AAA) [6, 7]. The incidence of intestinal ischemia in elective surgery for AAA and emergency surgery for ruptured AAA is reported to be 6% and 42%, respectively [6, 7]. In cases of suspected intestinal ischemia, however, it is not easy to make a treatment strategy of either revascularization or intestinal resection based on the inspection and digital palpation. ICG imaging system may provide an another useful

In this chapter, basic principles to the clinical applications of ICG imaging in cardiovascular

Indocyanine green is a hydrophilic tricarbocyanine dye that rapidly binds to plasma proteins in the body and is mostly incorporated to the liver and excreted in the bile [10]. As ICG in the blood is exposed to near infrared ray of 760- 780 nm wave length, it generates fluorescence of 800 - 850 nm wave length (Figure 1A, B) [10, 11]. Our preliminary study showed that the peak spectral absorption of ICG diluted in the human blood was at 760 - 780 nm (Figure 2) [12]. The amplitude of ICG fluorescent luminescence is not proportional to its concentration but is

**Figure 1.** ICG and fluorescent luminescence in various dilution. A: drug product of ICG (DiagnogreenTM; DaiichiSankyo Co., Tokyo, Japan). B: Fluorescent luminescence is not proportional to its concentration. The luminescence was highest

clue for decision-making [8].

82 Artery Bypass

surgery are described [9].

**2. Property of ICG**

at a concentration of 2.5 × 10-3 mg/mL.

highest at the ICG concentration of 2.5×10-3 mg/mL.

Fluorescence property of ICG has been used not only in ophthalmology as fluorescein fundus angiography to visualize retinal and choroidal circulation but for breast cancer surgery (sentinel node mapping), gastroenterological surgery, and cardiovascular surgery [8, 13, 14]. Following intravenous injection of ICG, fluorescence generated in the blood by near infrared light is captured by a camera and the vessels are visualized, although fluorescence is partially absorbed by the water and hemoglobin. This principle was applied to the commercially available intraoperative imaging system, SPY TM (Novadaq Technolo‐ gies Inc., Toronto, Canada) and Photodynamic Eye (PDE; Hamamatsu Photonics K.K., Shizuoka, Japan) [15, 16]. The PDE enable to image with a hand-held camera in the surgical

field. These devices visualize the blood flow clearly in monochrome imaging under irradiation of excitation light after ICG injection. The former emits a low-intensity laser (2.7 watts) and demonstrates angiographic image at a frame rate of 30 per second. They allow irradiation and recording time for up to 34 seconds but demonstrate the vessels in monochrome image. These systems have been applied to coronary and graft angiography [17] and peripheral arterial surgery [18].
