Ex vivo MRI of CAA Brain Hemispheres

Intact human brain hemispheres from 19 patients with definite CAA^{20 (link)} and 5 non-CAA control cases were included from an ongoing post-mortem MRI study at MGH. Details on the inclusion process, scanning procedures and tissue block sampling have been described previously.^{8 (link),30 (link)} In short, the hemispheres were fixed in 10% formalin for several weeks after autopsy. Prior to ex vivo 3T MRI, the hemispheres were placed in a plastic bag filled with periodate-lysine-paraformaldehyde and vacuum sealed. The samples were scanned overnight on a 3T MR system (Siemens, Magnetom trioTim syngo) using a 32-channel head coil. The protocol included a T₂-weighted turbo-spin echo sequence (TR, 1800 ms; TE, 61 ms; voxel size, 500 μm³ isotropic) and a gradient-echo fast low-angle shot (FLASH) sequence (TR, 20 ms; voxel size, 500 μm³ isotropic). Presumed ischaemic and haemorrhagic CC lesions were identified by the same raters (W.M.F. and S.J.v.V.) who were blinded to CAA severity or other histopathological findings. Inter-rater reliability for the presence of CC lesions was substantial [κ (95% CI) = 0.75 (0.48–1)].