MODEL FOR REGIONAL CEREBRAL OXYGEN DISTRIBUTION DURING CONTINUOUS INHALATION OF O-15(2), CO-O-15, AND CO2-O-15

  • 1 January 1978
    • journal article
    • research article
    • Vol. 19  (1) , 48-53
Abstract
Equilibrium positron brain scans were obtained during continuous inhalation of C15O, C15O2 and 15O2 in humans. Inhalation of C15O labels Hb, whereas C15O2 instantaneously labels stable water to H215O. During the continuous inhalation of 15O2, body tissues extract it from the blood in proportion to local metabolism and ultimately convert it to water of metabolism. After 6-8 min of inhalation, a steady-state equilibrium is established in which the inflow of tracer is balanced by its disappearance due to radioactive decay (T1/2 [half-life] = 2 min) and biologic removal. Mathematical models of the steady-state distributions of C15O, C15O2/H215O and 15O/H215O are derived. The steady-state distribution of C15O is insensitive to variations in blood flow and essentially measures blood volume. The distribution of H215O during inhalation of C15O2 is dependent, though nonlinearly, on blood flow. The distribution of H215O during inhalation of 15O2 depends linearly on the O2 extraction fraction and nonlinearly on blood flow. The dependence on blood flow in the 15O2 steady-state image can be removed by the division, point by point, of the 15O2 image by the C15O2 image.

This publication has 0 references indexed in Scilit: