Elastic behavior of brain tissue in vivo.

A measurement system and a test sequence have been developed to determine the in vivo elastic response of brain tissue in terms of a pressure-depth ratio. This parameter appears sensitive to changes in the tissue environment that may occur due to the influence of, e.g., anesthetic agents, hyperventilation, etc., and thus may be useful in evaluating such influences. The measurements are made with the dura-arachnoid membranes intact, thus maintaining the influence of the cerebrospinal fluid compartment on the response behavior of the brain tissue that comprises the subpial region. As an integral part of the test, the procedure also serves to determine the depth or position of the subpial region and thus assures that the subsequent pressure-depth measurements invole brain tissue response. Finally, some discussion is given to relating the measured pressure-depth ratio to the classical elastic modulus. Values of the pressure-depth ratio and the corresponding elastic modulus for seven dogs are given.