Clinical application of stable xenon CT-CBF studies without denitrogenation

Noninvasive and simplified methods for estimating regional cerebral blood flow (CBF) and regional partition coefficient (lambda) using the inhalation of stable xenon (Xes) and computed tomographic (CT) scanning are described. Thirty percent Xes in 70% oxygen was inhaled for 240 seconds and exhaled for 160 seconds during serial CT scanning without denitrogenation in 26 patients with cerebrovascular diseases and four volunteer controls. During the investigation, the end-tidal Xes concentration was continuously monitored with a thermoconductivity analyzer to determine the build-up range (A value) and build-up rate constant (K value) of the artery by the curve fitting method. Calculated A and K values were corrected by the following formulae reported previously: for patients aged 0-20 years, Ae = 0.75Aa + 2.15, Ke = 0.67Ka + 0.69; 21-40 years, Ae = 0.56Aa + 3.24, Ke = 0.38Ka + 1.12; 41-60 years, Ae = 0.91Aa + 1.95, Ke = 0.38Ka + 1.32; over 61 years, Ae = 0.52Aa + 3.81, Ke = 0.31Ka + 1.55 (Ae and Ke were calculated with end-tidal Xes concentration, Aa and Ka were calculated by direct sampling of arterial blood). A CBF map (f map) and lambda map made with corrected A and K values demonstrated reliable distribution. The CBF was high in the gray matter, low in the white matter, and much lower in the infarcted area. lambda was high in the white matter, low in the gray matter, and much lower in the infarcted area. Eight patients were examined with and without denitrogenation. Both the f map and lambda map with denitrogenation were compatible with those without denitrogenation.(ABSTRACT TRUNCATED AT 250 WORDS)