VALIDATION OF CONTINUOUS THERMAL MEASUREMENT OF CEREBRAL BLOOD-FLOW BY ARTERIAL-PRESSURE CHANGE

A thermal measurement system to monitor cerebral blood flow (CBF) cont inuously from the cortical surface is evaluated in vivo. It has a temp erature resolution of better than 0.001-degrees-C (1 m-degrees-C) and can compensate for baseline temperature fluctuations in the brain tiss ue. A new approach has been developed to test the capability of monito ring dynamic CBF response. Transient CBF changes associated with chang es in mean arterial blood pressure (MABP) caused by repeated bolus nor epinephrine injections are used to examine the response of the measure ment system in both the heated mode, sensitive to flow, and the unheat ed mode, sensitive only to temperature. Experiments on 13 rats demonst rate that changes in the MABP are closely correlated with those of tem perature difference in the heated mode. Regression analysis shows a me an slope of 0.9 m-degrees-C/mm Hg in the heated mode, which is signifi cantly different from zero (p < 0.002) and from the mean slope in the unheated mode (p < 0.002). This indicates that flow signal in the syst em output can be distinguished from the baseline thermal fluctuations. Thus, the system can be used to detect and study dynamic perfusion ch anges from the brain surface with minimal tissue damage. Furthermore, analysis of the data shows that the transient flow signal before autor egulation is linearly correlated with changes in MABP.