Overview of approach
Achieving accurate correlation of cortical atrophy and amyloid burden throughout the brain depends on obtaining a near-exact coregistration of PET to MRI, such that the cortical ribbon from each modality shares considerable overlap (≥ 50%). Thus, if the mean cortical thickness is 2–3 mm, the accuracy of coregistration needs to be on order of 1 mm. To achieve this accuracy, three sources of potential error must be addressed. The first is the considerable difference in spatial resolution between the modalities (approximately 1 mm for MRI and 6–8 mm for PET). The second involves the markedly different tissue contrast characteristics of the two modalities; although many algorithms can accurately coregister two scans using the same modalities, the accuracy is understandably lower when coregistering scans from different modalities, such as PET and MRI. The…
