MRI-Guided SPECT Perfusion Measures and Volumetric MRI in Prodromal Alzheimer Disease

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Abstract
SINGLE-PHOTON EMISSION computed tomography (SPECT) reveals perfusion abnormalities in patients with established Alzheimer disease (AD).1-4 The most consistent finding reported in these studies is decreased perfusion in the temporoparietal association neocortex in mildly and moderately impaired patients with probable AD compared with healthy controls. More recently, several research groups have attempted to identify brain perfusion patterns that predict subsequent development of AD. These efforts have practical, as well as theoretical, significance, because early prediction of AD would make it possible to implement strategies to prevent or delay dementia. Johnson et al5 used principal component analysis to identify decreased perfusion in the hippocampal-amygdaloid complex and in the anterior and posterior cingulate in prodromal AD. This approach does not require a priori assumptions about the locations of discriminating regions, but it may not yield insight into the role of particular brain structures in the development of AD. Other SPECT studies6,7 targeted specific volumes of interest (VOI) and reported that perfusion in the posterior cingulate declines in prodromal AD. None of these studies targeted all of the small brain regions believed to be involved in prodromal AD. Several magnetic resonance imaging (MRI) studies8-13 have, similarly, sought to determine whether decreased volume in certain brain structures characterizes prodromal AD. Significant volume changes in the entorhinal cortex and the hippocampus are the most commonly reported finding.8-13