Functional neuroimaging techniques such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) produce images of biological processes of the body. PET and SPECT detect functional differences between normal and malfunctioning neurobiology and neurochemistry. Unlike other brain imaging techniques, PET and SPECT can reveal disease related biological changes several years before the onset of symptoms and well before the other imaging techniques. The e.cam® family of SPECT systems, the e.camduet™ capable of both PET* and SPECT imaging or the ECAT® family of PET scanners image a single organ, like the brain, or every organ in the body in a single examination. Perhaps, the most exciting new aspect of nuclear medicine is the biographTM which combines the premier technologies of PET and computed tomography (CT) to reveal detailed anatomy and biological processes, both in a single examination.

Traditional radiological techniques typically indicate normal brain structure of a patient with a neurodegenerative disease, such as Alzheimer’s or Parkinson’s disease, although the biological failures of the disease and aging are present. When using PET to diagnose and manage Alzheimer’s disease not only is cerebral metabolic capacity reduction measured but also the disease is differentiated from normal aging effects.

*PET by method of coincidence detection.

Above are PET scans of cerebral metabolic function in a normal 68 year old (left) and a 65 year old subject with Alzheimer's disease (center) whose MRI (right) is indicates normal brain structure. In the PET scans, red indicates high metabolism with orange, yellow, green, and blue indicating progressively lower metabolic values. The arrows indicate metabolic deficits that are the hallmark of Alzheimer's disease as depicted by PET. These same areas revealed subtle metabolic deficits in asymptomatic subjects with relatives who are afflicted with Alzheimer's and have inherited the APO-E4 gene. This method is an effective way to detect Alzheimer's disease preclinically and test preventive therapies before permanent and extensive brain damage occur.

SPECT brain imaging is useful for detection of altered regional cerebral perfusion as in dementia or stroke. Occasionally, the need arises to differentiate ischemia from epilepsy as the cause of a transient neurological deficit. Ischemia causes an area of hypoperfusion on SPECT, whereas during epileptic discharges the activated neuronal pool elicits hyperperfusion. SPECT and PET imaging of the dopaminergic deficit in nigrostriatal system may improve the early and differential diagnosis of patients with Parkinsonism.

 PET and SPECT imaging are simple procedures that are useful in the following ways:

• To assess the extent and severity of brain pathologies.
• To enable early and accurate diagnosis of neurologic disease.
• To facilitate earlier initiation of neuroprotective treatment.
• To monitor the progression and therapy of neurological disease.
• To help to avoid unnecessary treatment of patients with obscured diagnosis.
• To aid in the development of new therapies.

Siemens nuclear medicine scanners are designed with unmatched technical innovation to deliver proven clinical utility and superb diagnostic results.