Determination of the spatial distribution of major elements in the rat brain with X-ray fluorescence analysis

An energy dispersive X-lay fluorescence analysis was applied for determinin g the spatial (two-dimensional) distribution of elemental concentrations in rat brain sections. Freeze-dried brain sections prepared from normal and i schemic rats with middle cerebral artery occlusion were scanned with a coll imated X-ray beam (0.18 mm in diameter, 50-kV acceleration voltage). The fl uorescent K alpha X-lays of P, S, Cl, and K were detectable, so that the tw o-dimensional distribution of fluorescent X-ray intensities could be determ ined for these elements. Furthermore, quantitative determination was possib le for P and K by using the fundamental parameter technique. However, the a ccurate determination of Na and Ca was difficult, because of the low energy of K alpha X-ray of Na, and the interference of K-K beta with Ca-K alpha. The change in elemental concentrations in ischemic tissue, including the de crease in It concentration and increase in Cl concentration, was demonstrat ed by this method as a two-dimensional contour map. Since it is possible to obtain a pictorial representation of the elemental concentration in tissue sections, this method may be useful to evaluate the ionic changes in injur ed brain tissue in relation to histological or autoradiographical observati ons. (C) 2000 Elsevier Science B.V. All lights reserved.