NONINVASIVE CEREBRAL OPTICAL SPECTROSCOPY - DEPTH-RESOLVED MEASUREMENTS OF CEREBRAL HEMODYNAMICS USING INDOCYANINE GREEN

To investigate the feasibility of a newly developed, near-infrared opt ical spectroscopy device, we analysed measurements of the infrared tra cer indocyanine green (ICG) using sensors with a single near infrared light source and multiple light detectors. Two mi of ICC dye, 1.0 mg m l(-1) in concentration, were injected into the internal carotid artery during cerebral angiography in 14 adult patients. The resultant washo ut curves were measured bilaterally using sensors with 4 detectors spa ced at 10, 20, 30 and 40 mm from the infrared light source on the righ t side, and 15, 25, 35 and 45 mm from the source for the left side, re spectively. Washout curves were analysed to determine the relative amp litude of the ICC absorption signal and deduce each detector's penetra tion distance. When ICC was injected into the internal carotid artery, relative absorption increased with detector distance from the light s ource. No substantial difference in attenuation was observed in any of the detectors during external carotid injection of ICC. The resultant information related depth of penetration of the light with source-det ector separation distances. The feasibility of the system for measurin g cerebral oxygen saturation and haemodynamics noninvasively or monito ring at bedside is discussed.