Comparison between cortical distribution of I-123 iomazenil and Tc-99m HMPAO in patients with Alzheimer's disease using SPECT.
OBJECTIVE
To compare brain perfusion and synaptic density in Alzheimer's disease assessed using I-123 iomazenil SPECT with brain perfusion assessed using Tc-99m HMPAO SPECT.


METHODS
Early and delayed I-123 iomazenil SPECT images acquired 20 and 180 minutes after injection were compared with Tc-99m HMPAO SPECT studies acquired 15 to 20 minutes after injection in five patients with Alzheimer's disease.


RESULTS
Visual analysis of I-123 iomazenil images showed more severe (n = 4) and extensive (n = 3) defects than did Tc-99m HMPAO. Semiquantitative analysis was performed by normalizing the uptake of Tc-99m HMPAO and I-123 iomazenil in individual brain regions in the cerebellum and expressing these values as a ratio of the occipital regions. The analysis of brain regional ratios in Tc-99m HMPAO studies showed a low but significant correlation with ratios of delayed (r = 0.325, P < 0.05) images in the I-123 iomazenil studies. Furthermore, when compared with Tc-99m HMPAO, early (P < 0.01) and delayed mean ratios (P < 0.05) were significantly less in the frontal regions; early mean ratios were significantly less in the temporal regions (P < 0.05), and delayed (P < 0.05) mean ratios were significantly less in the parietal regions.


CONCLUSIONS
Tc-99m HMPAO images were better correlated with I-123 iomazenil images, indicating cortical synaptic density (delayed images). I-123 iomazenil SPECT in patients with Alzheimer's disease provided more sensitive information than Tc-99m HMPAO, allowing evaluation of brain perfusion and synaptic density.
Varrone
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The Center for Nuclear Medicine of The National Research Council, University Federico II, Naples, Italy.
Soricelli
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Postiglione
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Salvatore
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D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D005260:Female; D005442:Flumazenil / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D019690:Technetium Tc 99m Exametazime / Q000493:pharmacokinetics*; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; D019690:Technetium Tc 99m Exametazime; D005442:Flumazenil; C063038:iomazenil