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The brain is a very complex organ and its complexity does not end with its structural and chemical composition. The brain is a dynamic organ and is in a constant state of change, governed by life’s experiences. Every time we learn something new, form a memory, experience stress or disease, the biochemical structure of our brain changes at the neuronal level and this affects information flow.
There are many varieties of brain disorders that affect humans, including dementia, epilepsy, and other disorders that are more generally thought of as being “behavioral” rather than biological.
Diagnosis of a brain disorder is based on symptoms, medical history, physical examination, risk factors, and clinical tests. Diagnostic procedures may be needed to confirm a diagnosis and imaging tests such as computed tomography (CT), magnetic resonance imaging (MRI), angiography, positron emission tomography (PET), and Doppler ultrasonography are commonly used to diagnose neurologic disorders.
Early research and clinical applications of PET imaging were almost exclusively devoted to the brain, and provided immense amounts of data that have advanced the understanding of brain function, and changes in regional glucose metabolism.
MRI and CT scans render exquisite anatomical detail about the structure of the brain, but are unable to determine anything about its function. PET/CT imaging can help physicians detect functional abnormalities early in the course of the disease, before anatomical changes occur. Brain disorders start with functional abnormalities that result in either an increase or decrease in glucose metabolism at a cellular level. These functional changes precede the formation of an abnormal mass, the shrinkage of brain tissue, or other abnormalities seen on anatomical imaging, sometimes by years.
PET/CT imaging can show precise areas of increased or decreased glucose metabolism in the brain. In Alzheimer’s disease for example, there is a characteristic pattern of decreased biomarker uptake in the posterior parietotemporal cortex, which could be caused by neuronal depletion in that area. Physicians use this type of information to differentiate Alzheimer’s disease from fronto-temporal and other dementia.
In a patient who experiences epileptic seizures, between seizures the PET scan displays decreased metabolism in the area of the seizure focus, but increased metabolism in that same area during a seizure. Physicians utilize this information to pinpoint the focus of a seizure prior to surgery.
PET provides valuable information for patients with neurological disorders.
Source: Atlas of Clinical Positron Emission Tomography by Sallie F. Barrington, Michael N. Maisey and Richard R. Wahl. Oxford University Press, Inc. New York, NY.
Source: Positron Emission Tomography: Basic Science and Clinical Practice. Peter E. Valk, Dale L. Bailey, David W. Townsend, Michael N. Maisey. Springer-Verlag London Limited.