Diagnosis of functional loss using with PET or SPECT

Described are outlines of positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging, and their application to diagnosis of brain diseases accompanying functional loss. PET imaging by annihilation photons is useful to see the brain metabolic activity with use of compounds labeled by positron emitters like 11C, 15O, 13N and 18F. Cerebral blood flow (CBF), CB volume and oxygen extraction fraction correlate well with the cerebral activity and can be measured by PET with C15O2, H215O or 15O2. 18F-glucose is usable to measure the cerebral metabolic rate of glucose. SPECT imaging by γ-rays of 133Xe, 123I-iofetamine (IMP), 99mTc-hexamethyl propylene amine oxime (HMPAO) and 99mTc-ethyl cysteinate dimer (ECD) is useful also to measure CBF in different mechanisms from agent to agent, which often reflect the pathophysiology of the lesion in problem. These imaging techniques are applied to the diagnosis of regional functional loss in ischemic brain diseases like infarction, dementia (Alzheimer and multiple vascular) and Parkinsonism, of which characters and details of actual images are presented herein. Authors say that although the imaging diagnosis for brain functional loss has progressed, the integration of neurological finding, clinical process and simple morphological brain image as well is still important in the routine examination. (K.T.)