Diagnostic value of FDG-PET and HMPAO-SPET in patients with mild dementia and mild cognitive impairment:: Metabolic index and perfusion index

Objective: The diagnostic potential of F-18-2-fluoro-2-deoxy-D -glucose positron emission tomography ( PET) and technetium-99m hexamethylpropylene amine oxime single-photon emission tomography (SPET) in early detection and differential diagnosis of early dementia was evaluated including a comparison of metabolic and perfusion indices ( PI). Methods: Twenty-four patients with initial clinical suspicion of beginning dementia were examined, 12 of them with mild cognitive impairment. All patients underwent SPET and PET within 2 weeks. Data were compared with the final clinical diagnosis at follow-up - 9 with Alzheimer's disease ( AD), 1 with frontotemporal dementia, 1 with vascular dementia ( VD), 7 with mixed type of dementia ( MIX) and 6 without any type of dementia. Metabolic indices (MI) and PI were compared with each other. The regional cerebral blood flow difference (rCBFdiff) calculated as local uptake difference between the right and left hemisphere was measured for patients with VD and MIX. Results: PET showed higher sensitivity and specificity in identifying the different types of early dementia ( 44 - 91 and 78 - 89%, respectively) than SPET ( 11 - 64 and 79 - 89%, respectively), especially in detecting AD ( sensitivity 44%, specificity 83%) and MIX ( sensitivity 71%, specificity 78%). Especially in patients with mild cognitive impairment, PET was the superior imaging modality for predicting dementia. Using PET, dementia could be excluded in all patients who did not develop dementia during the follow-up. In all patients, a weak correlation between PI and MI was observed ( rho = 0.64, p < 0.002). The rCBFdiff in patients with VD and MIX ranged from 7 to 37%. Conclusion: In this study on patients with initial suspicion of beginning dementia who underwent both imaging modalities, PET and SPET, PET was the superior imaging method, especially in the detection of early AD or MIX. Copyright (C) 2005 S. Karger AG, Basel.