Radionuclide Imaging in Ischemic Stroke

PET images of CBF, CMRO₂, and OEF in patients with acute ischemic stroke. (Left 2 columns) Areas with preserved OEF are not infarcted and can survive in spontaneous course (posterior part of ischemic cortex in patient 1, anterior part in patient 2 as indicated on CMRGlc and on late MR imaging and CT). (Right 2 columns) In patients receiving rtPA treatment, measurements of CMRO₂ and OEF are not feasible, but flow determinations show effect. If reperfusion occurs early enough and before tissue damage, tissue can be salvaged (patient 3). If reperfusion is achieved too late, tissue cannot be salvaged despite hyperperfusion in some parts (patient 4).

¹¹C-flumazenil distribution and ¹¹C-flumazenil binding in patients with large ischemic areas and effect of rtPA treatment. In patient 6, with area of decreased ¹¹C-flumazenil (FMZ) binding indicating irreversible damage, rtPA was not effective and large malignant infarction developed (late cranial CT [CCT]). In patient 2, with no significant decrease of ¹¹C-flumazenil binding in area of low blood flow, reperfusion by rtPA was successful and no infarction is seen on late CT.

Coregistered images of multitracer PET (top row) and MR PWI and DWI (middle row) in patient with severe right-sided hemiparesis and aphasia 4 h after onset of left middle cerebral artery stroke. Penumbra is characterized by hypoperfusion (CBF), preserved CMRO₂, and elevated OEF (top row). These findings correspond grossly to mismatch between DWI hyperintensity in anterior and deep parts of middle cerebral artery territory and PWI delay of 4 s in posterior parts compared with unaffected hemisphere. After rtPA treatment, demarcation of small infarct on DWI on day 2 persisted on T2-weighted MR imaging (bottom row).

Crossed cerebellar diaschisis in acute human stroke and response to supratentorial reperfusion. In patient 1, crossed cerebellar diaschisis persisted despite marked supratentorial reperfusion or hyperperfusion. Infarct volume was 60 cm³, and clinical outcome was poor (National Institutes of Health Stroke Scale, 9 points). In patient 2, supratentorial reperfusion was accompanied by crossed cerebellar diaschisis decrease. Follow-up CT showed no infarct; outcome score on National Institutes of Health Stroke Scale was 0 points. (Reprinted with permission of (85).)

Representative case with carotid stenosis before and after stenting. (A) Preoperative left common carotid artery angiogram shows severe internal carotid artery stenosis (anteroposterior view). (B) Left carotid arterial stenting was performed, and postoperative angiogram reveals no significant residual stenosis (anteroposterior view). (C and D) Preoperative ¹²³I-isopropyl iodoamphetamine SPECT shows hypoperfusion (C) and low cerebrovascular reactivity after acetazolamide (D) in both hemispheres. In right hemisphere, steal phenomenon is detected (D). (E and F) Postoperative SPECT obtained 3 mo after carotid arterial stenting demonstrates increased resting CBF (E) and cerebrovascular reactivity (F) on both ipsilateral and contralateral carotid occluded sides. (Reprinted with permission of (80).)