Extraction of Flow Information in Choriocapillaris in Human Eyes From ICG Dye Angiography Images

Abstract

Indocyanine green (ICG) dye angiography has been used by ophthalmologists as a useful tool for routine examination of the vasculature of the choroid in human eyes. ICG dye angiography is performed by venous injecting of ICG dye, which is delivered to different vascular structures in the eyes at different times. A multi-spectral fundus camera is used to take the dye intensity images of the eye at a speed of thirty images per second. In this study, a new approach is developed to extract information of velocity distribution in the choriocapillaris and its feeding blood vessels from the ICG dye angiograms. The ICG dye intensity rise and decay curves are constructed from the ICG dye images at each image pixel location in the choriocapillaris. It is shown that the magnitude of the local velocity in the choriocapillaris is proportional to the transient of the ICG dye intensity curve. The approach allows the determination of the absolute value of the velocity in the choriocapillaris and is calibrated by the image data at two axial locations of a straight blood vessel of uniform cross-section area. The velocity image of the entire choriocapillaris is then constructed. This approach could be used in clinical applications for diagnostic purposes since it provides detailed quantified flow information in human eyes.