**2. Property of ICG**

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

**Figure 2.** Absorbance and fluorescence value of ICG. ICG emits a flash of light with a wavelength of 806nm. The peak

Intraoperative ICG Angiography in Cardiovascular Surgery

http://dx.doi.org/10.5772/55311

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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

spectral absorption of ICG diluted in human blood is 760 - 780 nm.

**3. ICG angiography**

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

**Figure 2.** Absorbance and fluorescence value of ICG. ICG emits a flash of light with a wavelength of 806nm. The peak spectral absorption of ICG diluted in human blood is 760 - 780 nm.
