A technique for differential photoelectric plethysmography of brain and ear

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Abstract
A technique for implantation and apparatus for obtaining a circulatory pulse volume wave from the surface of the cerebral cortex of animals in both acute and chronic experimental situations are described. Fiber optic light guides are placed through burr holes on the brain surface and the skull closed with cement, thus restoring the Munro-Kellie principle. Heatless light is conducted into the brain and changes in optical density of this tissue due to vascular pulsation are converted to wave forms by a photoelectric pickup. Trauma and tissue reaction are minimal. Attachment of a similar plethysmograph to the ear by means of Teflon button receptacles allows differential recording of plethysmograms from either vascular bed. fiber optics; photoelectric technique; Munro-Kellie principle Submitted on March 5, 1964