Effect of the end-tidal xenon correction method on cerebral blood flow determination

The objective of this work is to show how the end-tidal xenon correction method contributes to determining the cerebral blood flow (CBF) values. Respiratory xenon data from 443 patients (mean age, 59.1 +/- 13.5) were analyzed using two methods: the conventional fitting method and the end-tidal correction method. For both methods, xenon saturation rate constant (Ka1) and desaturation rate constant (Ka2) were calculated for washin and washout phases respectively. By applying the correction method, both the histograms for Ka1 and Ka2 change significantly; they become to have narrower distribution with smaller mean value. As the average effect based on computer simulation, if calculated CBF values using corrected Ka1 and Ka2 are 80 cc/100 g-tissue/min for the gray matter and 20 for the white matter, those using conventional Ka1 and Ka2 become 62.8 for the gray matter and 17.9 for the white matter. By applying the end-tidal correction method, obtained CBF values increase, and the extent of increase is larger when xenon inhalation speed is slower.