Abstract

The direct and indirect contribution of brain haematoma to the near infrared spectroscopy instrument signal has been investigated by both experiment and Monte Carlo prediction. Absorption change by the haematoma (the direct effect) strongly contributes to change in both intensity and mean time of flight of the detected signal when the haematoma is located at or near the surface of the brain. In cases where the haematoma is located more than 10 mm below the brain surface the direct signal effect is negligible. However the haematoma is still indirectly detectable if it causes brain swelling because the detected light intensity is very sensitive to changes in the CSF thickness.

© 1998 Optical Society of America