Analysis of reproducibility of the 133Xenon inhalation method
Part II : Factors influencing CBF reproducibility
1982 Volume 4 Issue 1 Pages 38-43
Details
1982 Volume 4 Issue 1 Pages 38-43
The reproducibility of the cerebral blood flow (CBF) values measured by the non-invasive 133xenon inhalation method was reported in our previous article. The purpose of this investigation was to clarify the effects of various factors upon the reproducibility of this method. Two measurements of regional CBF were made at 13 locations in each hemisphere by the 133Xe inhalation method in 19 subjects with an age range of 19 to 83 years (mean age 51), with an interval of 10 to 70 minutes between the serial runs in each subject. The blood flow of the fast compartment (gray matter) of the brain (F1) was calculated as well as the initial slope index (ISI), as a flow index of predominantly gray matter, the relative weight (W1) and the fractional flow (FF1) of the fast compartment.
The mean value of hemispheric F1 or ISI of the second measurement was significantly smaller than that of the first measurement.
The variation coefficient (V.C.) of the change of regional F1 or ISI value was closely related to the geometric mean (MC) of maximal count rate per 5 seconds recorded from the same region in the first and second measurements.
The values of V.C. of the changes of regional F1 and ISI from regions with MC of 1000 or more were 15.6 and 14.6, respectively. Those from regions with MC of 1400 or more were 11.6 and 10.4, respectively. These values were smaller than the V.C. of the changes of regional F1 (19.1) and ISI (15.2) from all regions. The correlation coefficient of regional F1 in the first and the second measurements from regions with MC of 1400 or more was 0.86, whereas that of regional F1 from all regions was 0.76.
From these data, it appears that a high count rate of 1000 to 1400 counts or more per 5 seconds is essential if good reproducibility is to be obtained.
