Clinical utility of spatially normalized PET and SPECT to evaluate patients with memory and cognitive impairments

We assessed cerebral metabolism and blood flow in patients with memory and other cognitive impairment using the easy Z score imaging system (eZIS) and statistical parametric mapping (SPM) of FDG-PET and SPECT scans. Twenty patients with dementia (12 Alzheimer's disease (AD), 3 diffuse Lewy body disease (DLB), and 2 frontotemporal dementia (FTD)) and twenty with diffuse axonal injury (DAI) and cognitive impairments were studied with FDG-PET and ECD-SPECT. All images were analyzed using eZIS with the same processing procedures, including smoothing, normalization, and z-transformation, and compared to a database of normals. Z score maps were super-imposed on 3D MRI brain images. Group analyses were performed using SPM. Age-related declines in cerebral metabolism and blood flow were observed in the anterior cingulate association area. In contrast, reductions in these cerebral functions correlated best with severity of AD in the posterior cingulate association areas. In DLB and FTD, eZIS analysis of PET and SPECT revealed reductions of cerebral functions in specific areas. DAI showed low metabolism and blood flow in mesiofrontal cortex including the anterior cingulate association area. Dysfunction of the anterior cingulate association area in DAI, which resembled age-related cognitive decline, may be responsible for cognitive impairments. Overall, PET and SPECT scans showed significant correlations according to the type of dementia. Spatially normalized maps contributed to PET and SPECT image interpretation for patients with memory and cognitive impairments because better 3D visualization allowed more objective and systematic investigations. (author)