INVESTIGATION OF BLOOD-BRAIN-BARRIER PERMEABILITY BY MEANS OF COMPUTERIZED IMAGE-ANALYSIS

Intravital fluorescence microscopy has been widely used to study chang es of blood-brain barrier (BBB) permeability in vivo. However, quantif ication of tracer extravasation by counting leaky spots provides only a rough estimate of permeability increase. We have therefore developed a new method for measurement of tracer extravasation from cerebral bl ood vessels by combining image analysis techniques with intravital flu orescence microscopy. This method is based on generation of subtractio n images after shading and displacement correction. Subtraction images are further processed to eliminate noise and diminish artefacts due t o vessel distortion and/or dilatation. The <<degree of extravasation>> (E(f) value) which is then calculated takes into account the number a nd size of leaky spots as well as their intensities. Examples are show n to illustrate that pure vasodilatation does not increase E(f) as lon g as the BBB-permeability is not disturbed. This newly developed metho d may prove helpful for comparison of tracer extravasation under diffe rent experimental conditions.