Biomedical subjects

Etsuko Imabayashi

Publications and source records attributed to Etsuko Imabayashi.

21 records · Page 2Linked to original sources

PubMed2003

Correction for partial-volume effects on brain perfusion SPECT in healthy men.

UNLABELLED: The limited spatial resolution of SPECT scanners does not allow an exact measurement of the local radiotracer concentration in brain tissue because partial-volume effects (PVEs) underestimate concentration in small structures of the brain. The aim of this study was to determine which brain structures show greater influence of PVEs in SPECT studies on healthy volunteers and to investigate aging effects on SPECT after the PVE correction. METHODS: Brain perfusion SPECT using (99m)Tc-ethylcysteinate dimer was performed in 52 healthy men, 18-86 y old. The regional cerebral blood flow (rCBF) was noninvasively measured using graphical analysis. SPECT images were corrected for PVEs using gray-matter volume, which was segmented from coregistered MR images and convoluted with spatial resolution of SPECT scanners. Absolute rCBF data were measured using a 3-dimensional (3D) stereotactic template for regions of interest on anatomically standardized SPECT. We examined correlation of advancing age with rCBF before and after the PVE correction. To validate the correction method for PVEs, a Hoffman 3D brain phantom experiment was also performed. RESULTS: The PVE correction remarkably reduced the coefficient of variation for SPECT counts in the whole phantom. The PVE correction made the rCBF distribution more homogeneous throughout the brain with less intersubject variation than the original distribution. There were significant negative correlations between age and adjusted rCBF in the bilateral perisylvian and medial frontal areas. These correlations remained significant after the PVE correction. Instead of a positive correlation in the medial temporal structures between age and adjusted rCBF before the PVE correction, the sensorimotor and parietal areas mainly showed positive correlations after the correction. CONCLUSION: SPECT data reflect both brain volume loss and functional changes. Use of the PVE correction in brain perfusion SPECT provides a more accurate determination of rCBF even in healthy volunteers.

Adolescent↗

PubMed2002

Brain SPET abnormalities in Alzheimer's disease before and after atrophy correction.

The aim of this study was to determine which brain structures show the greatest influence of partial volume effects (PVE) in single-photon emission tomography (SPET) studies on Alzheimer's disease (AD). Brain perfusion SPET was performed in 30 patients with probable AD and 62 age-matched healthy volunteers. SPET images were corrected for PVE using grey matter volume segmented from magnetic resonance images. The most prominent changes after PVE correction were observed in the medial temporal structures. The PVE correction revealed a selective decrease in regional cerebral blood flow (rCBF) in the parahippocampal gyrus of AD without rCBF decreases in the hippocampus, which had been observed before correction. This correction seems to be essential in order to achieve accurate measurements of rCBF in SPET, which has limited spatial resolution.

Aged↗

PubMed2002

Longitudinal evaluation of both morphologic and functional changes in the same individuals with Alzheimer's disease.

UNLABELLED: Morphologic and functional imaging studies have not always given concordant results about brain areas showing atrophic changes and reduced flow or metabolism in Alzheimer's disease (AD). The aim of this study was to determine the initial abnormality and the longitudinal changes in both morphologic and functional measurements for the same individuals with AD. METHODS: We investigated 15 patients with mild AD and 25 age-matched healthy volunteers. The AD patients underwent both MRI and SPECT 3 times at intervals of approximately 1 y. The gray matter volume, as segmented from MRI, and the regional cerebral blood flow (rCBF), as measured by SPECT, of AD patients were compared with those of healthy volunteers using statistical parametric mapping, which is a voxel-based analysis in stereotactic space. RESULTS: Considerable discordance between areas of regional atrophy and areas of decreased rCBF was observed. The medial temporal areas showed a faster and more extensive reduction of gray matter volume than of rCBF. In comparison with the value at the baseline study, rCBF in the posterior cingulate gyrus and precuneus and the associative parietal cortex was extensively decreased. In contrast, the extent of significant decrease in this area continued to be much narrower for gray matter volume than for rCBF, even in the follow-up studies. Frontal areas, including the anterior cingulate gyrus and the orbitofrontal areas, showed a progressive reduction in both rCBF and gray matter volume. The reduction in rCBF was in a more posterior part of the associative temporal cortex than was the reduction in gray matter volume. CONCLUSION: These results indicate a distinct discordance between morphologic and functional changes in a longitudinal study of AD. Functional changes may be caused partly by remote effects from the morphologically involved areas with decreased connectivity and partly by a compensatory response by neuronal plasticity.

Aged↗