Method and apparatus for spectrophotometric cerebral oximetry and the

Abstract

Spectrophotometric apparatus and related methodology, including a sensor having a source and at least two receivers of electromagnetic radiation such as red and/or near-infrared light, which is applied non-invasively to the outer periphery of a patient or other animate test subject to examine a particular internal region to which is disposed beyond a peripheral extremity of specifically indeterminant thickness lying immediately inwardly of the outer periphery of the test subject. The location of the source and detectors test are selected to be at points spaced from one another by unequal first and second distances defining first and second mean optical paths of specifically differing length, with the second such path defining a primary internal area containing the particular region to be examined, the first optical path generally defining a second internal area located in the primary internal area but substantially separate from the particular internal region to be examined, and the first such optical path including the full thickness of a predetermined typical such peripheral extremity plus at least a small portion of the physiological substance immediately therebeyond. Signals are produced which are representative of the radiation detected by the first and second receivers, and such signals are processed to obtain data which particularly characterizes selected attributes of the substance within the particular internal region, substantially without effects attributable to the secondary internal volume, The second receiver is preferably disposed about thirty to forty millimeters from the source, and the first receiver positioned not closer than about twenty millimeters therefrom.