A, Inappropriate venous region-of-interest selection resulting in the CBV appearance mimicking global hypoperfusion. A, Inappropriate venous region-of-interest selection resulting in the CBV appearance mimicking global hypoperfusion. Perfusion was symmetric and normal following correct region-of-interest placement in the same patient (not shown). B, An example of appropriate placement of the AIF and VOF regions of interest is shown in the ACA and superior sagittal sinus, respectively. C, The corresponding normal findings on CBV are shown. Y.W. Lui et al. AJNR Am J Neuroradiol 2010;31:1552-1563 ©2010 by American Society of Neuroradiology