Radionuclide Imaging in Ischemic Stroke

Abstract

Learning Objectives: On successful completion of this activity, participants should be able to describe (1) the physiologic and metabolic variables relevant for brain function and the radionuclides and methods to measure these variables in cerebrovascular disease, especially ischemic stroke; (2) the radionuclide methods to determine the thresholds of flow and metabolism relevant for preservation of function and morphology and the obtained values in their relevance to prognosis and potential treatment; and (3) the applications of radionuclide imaging for identifying pathophysiologic changes responsible for extension of ischemic lesions, for defining the hemodynamic reserve in vascular disease, for detecting remote effects outside the primary lesions, and for locating compensatory activation in disturbed functional networks.Financial Disclosure: Dr. Heiss is supported by the Wolf-Dieter Heiss Foundation within the Max Planck Society. The author of this article has indicated no other relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, SAM, and other credit types, participants can access this activity through the SNMMI website (http://www.snmmilearningcenter.org) through November 2017.Ischemic stroke is caused by interruption or significant impairment of blood supply to the brain, which leads to a cascade of metabolic and molecular alterations resulting in functional disturbance and morphologic damage. The changes in regional cerebral blood flow and regional metabolism can be assessed by radionuclide imaging, especially SPECT and PET. SPECT and PET have broadened our understanding of flow and metabolic thresholds critical for maintenance of brain function and morphology: PET was essential in the transfer of the concept of the penumbra to clinical stroke and thereby had a great impact on developing treatment strategies. Receptor ligands can be applied as early markers of irreversible neuronal damage and can predict the size of the final infarcts, which is important for decisions on invasive therapy in large ("malignant") infarction. With SPECT and PET, the reserve capacity of the blood supply can be tested in obstructive arteriosclerosis, which is essential for planning interventions. The effect of a stroke on surrounding and contralateral primarily unaffected tissue can be investigated, helping to understand symptoms caused by disturbance in functional networks. Activation studies are useful to demonstrate alternative pathways to compensate for lesions and to test the effect of rehabilitative therapy. Radioisotope studies help to detect neuroinflammation and its effect on extension of tissue damage. Despite the...

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