| [PURPOSE] To map the specific foci site of Alzheimer's disease (AD) and Vascular dementia (VD) in the positron emission tomography (PET) brain imaging, as well to differential diagnosis AD and VD using PET.[ OBJECT AND METHODS ] There are 3 groups of subjects who were under strict clinical screening, 9 AD patients in group one, 11 VD patients in group two and 12 control subjects in group three. All subjects were studied with PET using I8F-FDG as radiotracer. And 4 other cases including possible mild AD and cognitive impairment also under discussed.Using visual analysis to summarise the characteristics of each group. Using Region of Interest( ROI) method to draw up each lobe of the cortex and the nerve nucleus under subcortical areas, then to calculate the ratio of each aera to the cerebellum. Comparing the results of group one and group three, group two and group three. And also comparing left/right side in each group.Using Statistical Parameters Mapping(SPM) method to analyze the PET data. The data were calculated to compare the results of group one and group three, also group two and group three after normalizing and smoothing. To find if there are regularites in the two diseases and to locate the lesion in the anatomic region, also in the Brodmann area.[ RESULTS ] Visual analysis shows that the hypometablism areas are including parietal lobe, temporal lobe and frontal lobe with left/right hemispheric asymmetry in the AD group, but spare the subcortical area. While in VD group, it shows that the hypometablism areas can be found in bothcortical and subcortical areas(especially in the infracted lesion), also asymmetry.ROI statistical results show that the radiocounts in the parietal lobe, temporal lobe and frontal lobe were significant lower in the AD patients than those in the control subjects (p<0.05) , the p value were as follows, parietal lobe: 0.0005 (left); 0.0462 (right), temporal lobe: 0.0001 (left); 0.0193 (right), frontal lobe: 0.0055(left); 0.0340(right). Other lobe in the cortex and subcortical areas were no significant changed. In VD patients, there were only left frontal lobe(p=0.0450) and right putamen(p=0.0232) showing lower radiocounts comparied with control subjects(this is realated to the infarcted area in VD patients).SPM results show that cerebral metabolic rate for glucose (CMRgl) decreased in parietal lobe(superior parietal gyrus, angular gyrus, supramarginal gyrus), temporal lobe(post middle temporal gyrus, post inferior temporal gyrus), frontal lobe(superior frontal gyrus, middle frontal gyrus, frontal pole, gyrus rectus, prefrontal region) and post cingulate bilaterally in AD patients compared with control subjects, and show right/left hemispheric asymmetry. The hypometablism areas correspond to Brodmann Area(BA) 7, BA39, BA40, BA20, BA21, BA37, BA9, BA10, BAH, BA12 , BA46 and BA23. The hypometablism spares basal ganglia, thalamus, cerebellum and primary sensory and motor cortical regions. In VD patients, the metabolic deficits were variable and asymmetric and can be found in both cortical(eapecially in the frontal lobe in this study) and subcortical areas.The other 4 cases' PET results are different with AD or VD's. The hypometablism corresponds to the brain dysfunction areas and has close relationship with the clinical symptoms.[ CONCLUSION ] PET can show a distinct typical pattern ofhypometablism in the AD patients, while no specific pattern in the VD patients and it can provide an effective imaging tool for the clinic to diagnose AD, also differential diagnose AD and VD.
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