Gamma camera imaging in ischemic diseases of CNS

Abstract

Molecular imaging with single photon emission computed tomography (SPECT) and positron emission tomography (PET) complement the anatomical information provided by computed tomography (CT) and MRI but their present day applications are limited. Present day applications of SPECT in neurology include perfusion studies in drug refractory epilepsy and to a lesser extent studies to access vascular risk. Technetium-99m (Tc-99m) hexamethylpropylene amine oxime (HMPAO), Tc-99m Ethyl cysteinate dimer (ECD) and iodine-123 (I-123) Iodoamphetamine (IMP) are lipophilic and cross the intact BBB. These tracers are effectively used to assess brain perfusion. Tc-99m HMPAO and Tc-99m ECD provide a snapshot of perfusion at the time of injection and therefore can be used to reflect the ictal state. Brain perfusion SPECT can be evaluated using a visually, semi-quantitatively and using voxel-based statistical techniques. Applications in evaluation of cerebrovascular disease include acute stroke wherein perfusion SPECT can provide valuable information with respect to complications, outcome and choice of treatment strategy. The others be vascular reserve assessment in patients with high stroke risk such as Moyamoya (MMD) and occlusive diseases. In chronic cerebrovascular disease rCBF SPECT with assessment of functional reserve (using cerebrovascular dilator challenge) may guide decisions regarding vascular interventions including surgery.