Figure 13:57-year-old male status post surgical clipping of a right MCA aneurysm. During the post-operative course, the patient developed “angiographic” vasospasm involving the distal right MCA (not shown). CTP shows minimally decreased parenchymal CBV (A) and CBF (B) in the right MCA territory with increased MTT (C) (arrows), consistent with ischemic tissue. Of note, there is decreased blood pool in the sylvian vessels resulting in slightly asymmetric CBV.