[Evaluation of factor for one-point venous blood sampling method based on the causality model].

PURPOSE: One-point venous blood sampling method (Mimura, et al.) can evaluate the rCBF value with a high degree of accuracy. However, the method is accompanied by complexity of technique because it requires a venous blood Octanol value, and its accuracy is affected by factors of input function. Therefore, we evaluated the factors that are used for input function to determine the accuracy input function and simplify the technique. METHODS: The input function which uses the time-dependent brain count of 5 minutes, 15 minutes, and 25 minutes from administration, and the input function in which an objective variable is used as the artery octanol value to exclude the venous blood octanol value are created. Therefore, a correlation between these functions and rCBF value by the MS method is evaluated. RESULTS: Creation of a high-accuracy input function and simplification of technique are possible. The rCBF value obtained by the input function, the factor of which is a time-dependent brain count of 5 minutes from administration, and the objective variable is artery octanol value, had a high correlation with the MS method (y=0.899x+4.653, r=0.842).

[Development of quantification analysis software for measuring regional cerebral blood flow by the modified split-dose method with (123)I-IMP before and after acetazolamide loading].

We developed a quantification analysis software program for measuring regional cerebral blood flow (rCBF) at rest and under acetazolamide (ACZ) stress by the modified split-dose (MSD) method with iodine-123 N-isopropyl-p-iodoamphetamine (IMP) and compared the rCBF values measured by the MSD method and by the split dose (123)I-IMP SPECT (SD) method requiring one continuous withdrawal of arterial blood. Since the MSD method allows the input of two arterial blood sampling parameter values, the background subtraction procedure for obtaining ACZ-induced images in the MSD method is not identical to the procedure in the SD method. With our software program for rCBF quantification, the resting rCBF values determined by the MSD method were closely correlated with the values measured by the SD method (r=0.94), and there was also a good correlation between the ACZ-induced rCBF values obtained by the MSD method and by the SD method (r=0.81). The increase in rCBF under ACZ stress was estimated to be approximately 26% by the SD method and 38% by the MSD method, suggesting that the MSD method tends to overestimate the increase in rCBF under ACZ stress in comparison with the SD method, but the variability of the rCBF values at rest and during ACZ stress analyzed by the MSD method was smaller than the variability with the SD method. Further clinical studies are required to validate our rCBF quantification analysis program for the MSD method.