Regional cerebral blood flow in man. I. A study of the xenon 133 washout method.

THE CLINICAL determination of the regional cerebral blood flow (rCBF), based upon the inert gas washout technique of Kety and Schmidt1and developed by Lassen, Ingvar, Ho-Rasmussen et al2-5has become an established procedure in many laboratories. This technique is currently advocated as the most physiologic means to measure regional blood flow and, therefore, is assuming increasing importance as an adjunct to carotid arteriography. Using a two compartment model, many investigators have calculated the washout curve as the sum of two exponents which has been said to estimate regional flow distribution between the white and gray matter, while others have used Zierler's6 mean λH flow calculations (f= A, where λ = the partition coefficient, H = the difference in height of the curve from 0-10 minutes, and A = the area under the curve). Both of these calculations require knowledge of the maximum height of the curve (Hmax). We