Issn Print: 0363-9762
Publication Date: 1999/03/01
REGIONAL CEREBRAL BLOOD FLOW (rCBF) MEASURED BY MULTIPLE SPECT ACQUISITIONS FOLLOWING A SINGLE INJECTION OF 99MTC-HMPAO WITH AND WITHOUT ACETAZOLAMIDE (ACZ).
Excerpt
Technetium-99m-HmPAO has been used to determine rCBF and cerebral vascular reserve capacity (CVRC) using SPECT imaging. We examined the kinetics of 99mTc-HmPAO in a normal volunteer as measured by multiple SPECT acquisitions following a single injection with and without ACZ. Three separate acquisitions were performed following the injection of 30mCi of 99mTc-HmPAO. On a second occasion, the same subject was pretreated with 1G of ACZ and six separate acquisitions were obtained following the injection of 30mCi of 99mTc-HmPAO. For each of the acquisitions, radioactive counts were measured in 12 discrete brain regions, as well as the whole brain slice. The 12 regions were established using magnetic resonance images (MRI) of this subject. The regions were stored and applied to each SPECT acquisition, which had been co-registered to the MRI using a validated volume registration algorithm. The data was corrected for radioactive decay and amount of radioactivity administered. The corrected radioactive counts in each region and the whole brain slice were compared at all time points for each group of images. Clearance from each region and the whole brain slice was estimated. Each region was normalized by comparison to the cerebellum. Using ANOVA, significant differences (P<0.05) were observed between time points in discrete brain regions, both with and without ACZ. This data suggests that comparisons of rCBF performed pre- and post-ACZ in order to estimate CVRC must be done with caution as the localization of the radiotracer is subject to biologic clearance mechanisms. Discrete brain regions demonstrate unique and variable rates of clearance. Further study of this phenomenon is warranted in a larger population.
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