[Measurement of regional cerebral blood flow by 133Xe inhalation method -experimental system and its evaluation of...

Noninvasive measurement of regional cerebral blood flow (rCBF) by 133Xe inhalation and simulation studies of the errors in analyzing 133Xe clearance curves were reported. Our system was based on Obrist's 10 minutes desaturation method after 1 minute inhalation of 185 approximately 222 MBq (5 approximately 6 mCi)/l of 133Xe gas mixed in the air. Clearance curves were simultaneously measured at six location in each hemisphere. End-tidal 133Xe curve used for correction of recirculation was generated from respired air curve. Values for rCBF were calculated by two compartment analysis of the head curves. We evaluated the experimental errors with computer simulation studies. The synthetic head curves were generated with a three compartmental model representing the fast and slow component in the brain and the extracerebral component. The arterial input function used was the end-tidal curves of a typical control subject. The results of computer simulation studies were obtained as follows: F1 that is the flow of the fast compartment in brain and adequate reliability; statistical errors for normal value of F1 (80 ml/100 g/min) were 5% at 30 kcpm; the optimum end point of curve-fitting was 10 approximately 11 minutes after 1 minute inhalation of 133Xe gas; the error due to remaining activities of repreceding study was 3% at the interval of 25 minutes between inhalation.