Shigeru Yamaji

Demonstration of decreased posterior cingulate perfusion in mild Alzheimer's disease by means of H215O positron emission tomography.

Although decreased posterior cingulate metabolism in Alzheimers disease (AD) has been previously reported, there have been no reports on posterior cingulate perfusion. In this study we evaluated posterior cingulate perfusion as a relative value using statistical parametric maps (SPMs) and as an absolute value using conventional region of interest (ROI) settings. Twenty-eight subjects, including 14 patients with mild AD (mean age: 66.4±12.1 years) and 14 normal controls (65.9±7.3 years) were studied. Regional Cerebral blood flow (CBF) was measured with H215O and positron emission tomography (PET). In the SPM analysis, the left posterior cingulate and left parietotemporal CBFs were significantly decreased in the patients with mild AD (P<0.001). At a louver statistical threshold (P<0.05), the right posterior cingulate and right parietotemporal CBFs were also significantly decreased in the AD patients. In the ROI studies, the left parietal and posterior cingulate CBFs in the patients with mild AD were significantly lower than those of the normal controls by analysis of variance and post-hoc Scheffés test (P<0.001). We conclude that posterior cingulate perfusion is decreased in mild AD, reflecting the pathological changes and metabolic reduction in the posterior cingulate gyrus that have previously been reported to occur in mild AD.

Relatively Preserved Hippocampal Glucose Metabolism in Mild Alzheimer’s Disease

The purpose of this study was to clarify the changes in hippocampal glucose metabolism in mild Alzheimer’s disease (AD) using positron emission tomography (PET) and 2-(18F)fluoro-2-deoxy-D-glucose (FDG). Forty-one patients with probable mild AD (age: 69.0 ± 8.0 years; MMSE: 22.6 ± 2.1) and 22 normal volunteers (age: 67.7 ± 7.1 years) were studied. The regional cerebral metabolic rate for glucose (CMRglc) was measured using FDG and PET. Although the mean CMRglc in the parietal region was significantly lower in the AD group (right: 6.35 ± 1.26 mg/100 g/min; left: 6.37 ± 1.21 mg/100 g/min) than in the control group (right: 7.73 ± 1.02 mg/100 g/min; left: 7.63 ± 0.95 mg/100 g/min), the mean CMRglc in the hippocampus did not show a significant difference between the AD group (right: 4.58 ± 0.70 mg/100 g/min; left: 4.63 ± 0.67 mg/100 g/min) and the control group (right: 5.22 ± 0.65 mg/100 g/min; left: 5.22 ± 0.67 mg/100 g/min) by analysis of variance and post-hoc Tukey’s test. The magnitude of the hippocampal CMRglc reduction was not as large as that of parietal CMRglc reduction. Statistical parametric maps (SPM) analysis also did not significantly demonstrate reduced hippocampal CMRglc in AD patients, although it did show a significant reduction in parietal CMRglc in AD patients. Hippocampal CMRglc was not significantly decreased in mild AD. This was unexpected in view of previous studies that have shown atrophy and clinical dysfunction concerning hippocampus in AD, and suggests that the pathophysiology of the hippocampus in AD may be more complex than was previously thought.

Tc-99m ethyl cysteinate dimer SPECT and 2-[F-18]fluoro-2-deoxy-D-glucose PET in Alzheimer's disease : Comparison of perfusion and metabolic patterns

PURPOSE This study compared Tc-99m ethyl cysteinate dimer (ECD) SPECT images with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) PET images in the same patients with Alzheimers disease and determined whether ECD SPECT is as useful as FDG PET clinically. METHODS Ten patients with probable Alzheimers disease (mean +/- SD: age, 71 +/- 5.2 years; 6 women and 4 men; Mini-Mental State Examination score, 19.2 +/- 5.3) were evaluated in this study. Both ECD SPECT and FDG PET were performed within 1.5 months in each patient. RESULTS ECD SPECT showed a reduction in parieto-temporal perfusion in 8 of the 10 patients, whereas FDG PET showed a reduction in temporoparietal metabolism in 9. The ECD images showed greater radiotracer uptake in the cerebellum and occipital lobe than did FDG images. The contrast between the radiotracer uptake in the sensorimotor area and that in the parietotemporal region was not as great in the ECD images as it was in the FDG images. CONCLUSION Although ECD SPECT may not be superior to FDG PET, it is useful for the clinical evaluation of patients with Alzheimers disease.

Evaluation of standardized uptake value to assess cerebral glucose metabolism.

PURPOSE When the cerebral metabolic rate of glucose (CMRglc) is to be measured, arterial blood sampling is usually required for fluorine-18 fluorodeoxyglucose (FDG) and positron emission tomography (PET) studies. However, blood sampling is inconvenient because it requires several staff members and is invasive for patients. METHODS To assess cerebral glucose metabolism by a noninvasive and simplified method, the authors used the standardized uptake value (SUV), which requires no input function or blood sampling. The study participants included 18 healthy volunteers (4 men and 14 women; mean +/- SD age, 68.2+/-6.3 years), 18 patients with mild Alzheimers disease (AD) (4 men and 14 women; mean +/- SD age, 68.8+/-7.3 years), and 18 patients with moderate AD (5 men and 13 women, mean +/- SD age, 69.5+/-8.5 years). Regional CMRglc and regional cerebral SUV were measured in the three groups using FDG PET, and the correlation between global CMRglc and global SUV was estimated. RESULTS The correlation coefficients of global CMRglc and global SUV in the healthy volunteers, mild AD patients, and moderate AD patients were 0.82, 0.67, and 0.62, respectively. Compared with the healthy persons, the patients with mild AD showed significantly decreased CMRglc in the temporal, frontal, and parietal cortices, but they did not show significantly decreased SUV in any region. Patients with moderate AD had significantly decreased CMRglc in the temporal, frontal, occipital, parietal, and sensorimotor cortices and significantly decreased SUV in the temporal, frontal, occipital, and parietal cortices. CONCLUSION The SUV would be useful as a semiquantitative index of cerebral glucose metabolism only in healthy persons or those with mild AD.

The clinical utility of visual evaluation of scintigraphic perfusion patterns for Alzheimer's disease using I-123 IMP SPECT

The authors examined the role of SPECT perfusion pattern in the diagnosis of Alzheimers disease (AD) using I-123 IMP. They studied 93 patients who had memory and cognitive disorders, including 42 patients with a diagnosis of probable AD, classifying SPECT images into determined perfusion patterns. The probability of AD was 54% with bilateral temporal and/or parietal defects, 69% with bilateral temporoparietal defects with additional defects, 17% with no defects, and 11% with frontal defects only. The sensitivity of bilateral temporoparietal perfusion defects for AD was 95.2%, whereas the specificity was 56.9%. In the absence of bilateral temporal and/or parietal defects on visual evaluation of SPECT, the diagnosis of AD was unlikely, although it is not pathognomonic for AD, because this sign would be seen in various neuropsychiatric diseases causing memory and cognitive impairments. Visual evaluation of SPECT is of value in the diagnosis of AD among patients with dementia.

Cerebral blood flow changes in the primary motor and premotor cortices during hyperventilation

The aim of this study was to clarify the regional differences in cerebral blood flow (CBF) change during hyperventilation by using H215O and positron emission tomography (PET). Eight healthy volunteers (age: 63.0 ± 8.9 yr.) were studied. Regional CBF was measured by the H215O autoradiographic method and PET. Statistical parametric maps (SPM) and conventional regions of interest (ROI) analysis were used for estimating regional CBF differences in the normocapnic state with normal breathing and the hypocapnic state induced by hyperventilation. Total CBF decreased during the hypocapnic state. The SPM revealed that primary motor and premotor cortices were significantly activated by hyperventilation. In these areas absolute CBF values were significantly higher than those in the temporal, occipital and parietal lobes in the hypocapnic state, but there were no significant regional differences in the normocapnic state. In the hypocapnic state induced by hyperventilation, the primary motor and premotor CBF shows combined changes with vasoreaction to hypocapnia and increase in activation due to hyperventilation.

Regional cerebral blood flow and oxygen metabolism in a patient with Korsakoff syndrome

We report a functional neuroimaging study of a patient clinically diagnosed with Korsakoff syndrome. Positron emission tomography (PET) with the15O inhalation method showed decreased regional cerebral blood flow (rCBF) and decreased regional cerebral metabolic ratio for oxygen (rCMRO2) in the bilateral fronto-temporal areas and in the left thalamus. These results suggest that dysfunction of the frontal-thalamic neural network plays a role in the disturbance of Korsakoff syndrome.