Abstract
Objective: Following tumour surgery in the head and neck region, skin flap transplants are usually required to cover the resection area. The purpose of the development was to provide a simple and reliable means to assess whether the transplanted flap is sufficiently perfused. Methods: Fluorescence of intravenously injected Indocyanine green (ICG) was detected with a slightly modified 3-chip CCD camera. Appropriately coated optical filters allow for excitation of ICG with NIR light and detection of NIR ICGfluorescence with the blue channel of the camera. In addition, low intensities of white light can be transmitted to allow for simultaneous display of a remission image in the green and red channels of the camera. Further processing was performed with a LabVIEW program. Results: A satisfactory white light image (red, green and blue display (RGB)) could be calculated from the remission images recorded with the green and red channels of the camera via a look-up table. The look-up table was programmed to provide an optimized blue intensity value for each combination of red and green values. This was generated using a reference image. Implementation of image tracking and intensity measurements in regions of interest (ROIs) in the images is useful to reliably monitor perfusion kinetics of flap and adjacent normal tissue.
Highlights
Endoscopic indocyanine green (ICG) perfusion imaging for flap transplants: technical development
Motion tracking and correction of fluorescence images with white light remission images enables endoscopic ICG-perfusion imaging with semiquantitative measurements
The restoration of a full-colour pseudo-white-light image from the green and blue channels was successfully established with minimal impact on colour perception
Summary
Endoscopic detection of fluorescence of indocyanine green (ICG) requires excitation in the NIR wavelength range 800nm. Commercial 3-chip endocameras can be made sensitive for the fluorescence emission in the blue channel by removing infrared blocking filters. It was the objective of the development to combine white light imaging (using the green and red channels only) and fluorescence imaging (using the blue channel) on a single 3-chip camera head. Reliable pharmacokinetics of ICG perfusion images should be established
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