Clinical Positron Emission Tomography (PET) Neuroimaging: Advantages and Limitations as a Diagnostic Tool

AND FIGURE 1.A common analytical approach in positron emission tomography (PET) imaging is to statistically compare a patient's PET images on a voxel-by voxel basis to a database of healthy individuals matched for age and gender (normative database).Voxels in which the patient differs by more than 2.5 standard deviations (Z-scores less than -2.5 or more than12.5)indicate areas of significantly altered function.1 Specificity and sensitivity of this approach can be affected by the size and patient population in the normative database, age adjustment, statistical methods, and the classification of the scan as normal or abnormal.Z score results are often displayed using a three-dimensional (3D) stereotactic surface projection system (3D-SSP).In this example, the Z-score results for fluorodeoxyglucose (FDG) PET imaging demonstrate the patterns of reduced metabolism characteristic of Alzheimer's disease (AD, yellow), frontotemporal dementia (FTD, pink) and dementia with Lewy bodies (DLB, blue) overlaid onto the lateral, medial and inferior surfaces of the brain.Note the predominately posterior pattern of hypometabolism in AD (asymmetric in this case, which is not unusual), involving the parietal and posterior temporal regions as well as the posterior cingulate gyrus.DLB has a similar pattern to AD.However, there is also involvement of the visual cortex.FTD has a predominantly anterior pattern involving the frontal lobes, anterior temporal lobes, and anterior cingulate gyrus.