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Cerebral blood flow (CBF) can be quantified noninvasively using the brain perfusion index (BPI), determined from radionuclide angiographic data generated with technetium-99m hexamethylpropylene amine oxime ( 99m Tc-HMPAO). Previously, the BPI has been calculated using graphical analysis (GA); however, the GA method is greatly affected by the first-pass extraction fraction and retention fraction, which are not only variable, but lower in cases with an increased CBF, such as after the administration of acetazolamide. Thus, GA-calculated BPI values (BPI G ) may not reflect the absolute CBF. The objective of this study was to use the spectral analysis of radionuclide angiographic data collected using  99m Tc-HMPAO to examine changes in the BPI after the administration of acetazolamide. We studied the CBF of both cerebral hemispheres in six healthy male volunteers; the BPI was measured at rest and after the intravenous administration of 1 g of acetazolamide. In all participants, an H 2  15 O positron emission tomography (PET) examination was also performed, and the spectral analysis—calculated BPI values (BPI S ) and BPI G  values were compared with the actual CBF measured using H 2  15 O PET (mCBF PET ). The BPI S  was 1.070 ± 0.051 (mean ± SD) at rest and 1.497 ± 0.098 after acetazolamide; the corresponding BPI G  values were 0.646 ± 0.073 and 0.721 ± 0.107. The BPI S  values were significantly correlated with the mCBF PET  values, whereas the BPI G  values were not. According to the BPI S  values, the increase in BPI after the intravenous administration of acetazolamide was 40.1 ± 8.4%, as opposed to an increase of only 11.3 ± 6.5% according to the BPI G  values. These results suggest that the spectral analysis of  99m Tc-HMPAO—generated data yields a more reliable BPI than GA for the quantification of CBF after acetazolamide administration.

Assessment of Acetazolamide Reactivity in Cerebral Blood Flow Using Spectral Analysis and Technetium-99m Hexamethylpropylene Amine Oxime