A review of indocyanine green fluorescent imaging in surgery

Abstract

The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

Figure 1

A typical ICGA image: heart of a rat. Coronary arteries clearly visible. Liver shining on the right. Magnification 20×. Image taken by Dr. Outi Villet at HUCH by our prototype microscope device shown in Figure 6.

Figure 2

Simple image processing and pseudocoloring: ICG-VA frames of a leg (toes up) after the injection of ICG: (a) at about 30 s showing deep lying arteries in red, (b) at about 60 s showing mainly capillaries in yellowish green, (c) at about 90 s showing mainly subcutaneous veins in blue, and (d) fusion of the first three images. Image processing steps: negative of the original image and some intensity remapping. Fusion by using CMYC model. For more information see [5]. The original B/W images were taken with PDE by Dr. Hiroaki Terasaki (visiting HUCH from Tokyo Medical and Dental University Hospital of Medicine) and later processed by one of the authors (P. Välisuo).

Figure 3

The transmission of the ICG filter pair (F _s: high-pass filter for source; F _c: low-pass filter (barrier) for camera) and the emission spectrum of two NIR LEDs having the nominal peak wavelengths of 780 and 850 nm and full width at half maximum (FWHM) bandwidths correspondingly of 30 and 95 nm.

Figure 4

The principle of fluorescence imaging. The radiation from the light source is filtered by a high-pass filter, F _s, to remove the fluorescent wavelengths. The blood and ICG suspension under a tissue absorbs the excitation wavelengths and emits in fluorescent band. The emitted light is received by the sensor through a low-pass filter, F _c, to remove the excitation light reflected from the source.

Figure 5

The quantum efficiencies of different sensor technologies in VIS-NIR range. iXon3 is an electron multiplier CCD, ER-150 LL is Hamamatsu biomedical CCD sensor, Neo is a scientific CMOS sensor, MT9V032 is a CMOS sensor for surveillance, KAI-11002 is a standard CCD sensor, and MT9P031 is a standard consumer CMOS sensor.

Figure 6

An old operational microscope used in our prototype ICG stereo video angiography system experiment. Hamamatsu NIR camera on the left camera arm.