Figure 2.

Definition of regions of interest (ROIs) for analysis of perfusion and oxygenation. (a) illustrates the sagittal view of the imaging volume of the GESFIDE sequence (bold white box) and the multi-delay ASL sequence (dashed box). Analysis was only performed on data from the GESFIDE imaging volume. ROIs were defined by summing adjacent slices to form two slabs, with center of the slabs illustrated at the levels of the cyan and yellow slices shown in (a). (b) illustrates an example case where the right MCA is occluded and the right ACA is stenosed, as indicated by the red arrows. At each level, six radial mixed-cortical segments were defined symmetrically to the midline, as shown in (c) and (d), shown superimposed on the T1-weighted anatomical images. Red segments correspond to angiographically abnormal ROIs, while green segments are angiographically normal ROIs.