CEREBRAL BLOOD-FLOW OF THE EXPOSED BRAIN SURFACE MEASURED BY LASER-DOPPLER PERFUSION IMAGING

A novel application of laser Doppler flowmetry (LDF), laser Doppler pe rfusion imaging (LDPI). was used to study cerebral cortical blood flow (CBFcortex). In contrast to the conventional laser Doppler perfusion monitor. LD Pi creates two-dimensional maps of the tissue perfusion in a well defined area of up to 120 x 120 mm comprising 4096 measurement points. Measurements of CBFcortex were made through an optically tran sparent polyester film applied to a cranial window preparation in vent ilated anaesthetized pigs. Temporal and spatial heterogeneity in CBFco rtex were visualized by LDPI during provocations which are known to al ter CBF (varying arterial Pco(2) or MABP. or infusion of adenosine at constant MABP (concomitant angiotensin administration) or by hyperoxem ia). During hypercapnia the recorded CBFcortex increased homogeneously . The adenosine-mediated increase in recorded CBFcortex was concentrat ed on the lower flow interval, as was the hyperoxemia-caused decline. At decreasing MABP the autoregulatory threshold was found to vary loca lly within the cortex. The results suggest that LDPI, apart from detec ting localized changes in CBFcortex, also visualizes flow changes with in different vascular segments. Together with the practical advantages of the system, i.e. not necessitating direct contact with the tissues , this feature makes the technique suitable for studies of CBFcortex d istributions.