FIG 2. Case 1: 59-year-old man with reversible ischemic neurologic deficit.

A, Anteroposterior view of right common carotid angiogram shows complete occlusion of the right proximal ICA.

B, T2-weighted image (3500/90/1) obtained at the level of perfusion MR imaging is normal except for subtle ischemic lesions in both occipital periventricular white matters.

C, CBV map shows slightly increased CBV in the right whole MCA distribution compared with contralateral corresponding region.

D, CBV map shows irregular ROIs placed for measurement of CBV ratio between the affected MCA territory and the contralateral region. Calculated CBV ratio was 1.04.

E, Corresponding uMTT map shows increased uMTT in the right whole MCA distribution compared with contralateral region.

F, ^99mTc-HMPAO brain SPECT scan obtained at approximately the same level as C and E reveals mild hypoperfusion throughout the right whole anterior and MCA territories.

G, ^99mTc-HMPAO brain SPECT scan with acetazolamide challenge reveals remarkable hypoperfusion in the right side as compared with F, suggesting reduced vascular reserve capacity in the right side.