Single photon emission computed tomography

Definition

Single photon emission computed tomography (SPECT) is an imaging study that uses radioactive materials injected through a vein that will pass into the brain generating a high-resolution brain image.

Description

SPECT is used to diagnose head trauma, epilepsy, dementia, and cerebrovascular disease. Development of a radiotracer called Tc99m label has increased the resolution of brain images generated from SPECT. The images yield very accurate spatial and contrast resolutions. The resulting sharp images enable the clinician to visualize very small structures within the brain. The accuracy of SPECT brain images makes it a very useful clinical and research tool.

Clinically, SPECT is useful for diagnosing the following disease states:

• Cerebrovascular disease or stroke: SPECT is useful to detect ischemia (reduced blood flow), determination of stroke causes, evaluate transient ischemia, determine prognosis, and monitor treatment.
• Dementia such as in Alzheimer's disease: SPECT studies can be used effectively to rule out other medical causes of dementia.
• Head trauma: Evidence suggests that SPECT is useful to detect greater number of lesions following the period after head trauma. It seems that the high resolution and accurate brain images of SPECT can detect lesions in the brain that are not possible to visualize using other techniques such as positron emission tomography(PET) scanning. SPECT images can give clinicians important information concerning prognosis (also sometimes called outcome) and treatment of persons affected with head injury.
• Epilepsy: The radioactive material injected before SPECT imaging concentrates at the seizure locus (the region that contains nerve cells that generate an abnormal impulse). This can help identify the location of seizuresand assist clinicians concerning management and outcomes.
• SPECT allows clinicians to visualize a specific area of the brain called the striatum, which contains a neurotransmitter (a chemical that communicates nerve impulse from one nerve cell to another) called dopamine. Circuitry in the striatum and interaction with dopamine can help provide valuable information concerning movement disorders, schizophrenia, mood disorders, and hormone diseases (since hormones require control and regulation from the brain in structures called the pituitary gland and hypothalamus).

As a research tool, SPECT imaging seems to be sensitive tool to measure blood flow through the brain (cerebral blood flow), in persons who have psychological disorder such as obsessive-compulsive disorder(higher blood flow) and alcoholism (lower blood flow).

Other dianostic indications and procedures are similar to other imaging studiessuch as computed tomography, magnetic resonance imaging, and PET.

PERIODICALS

Busatto, Geraldo, F. "Regional cerebral blood flow abnormalities in early-onset obsessive-compulsive disorder: an exploratory SPECT study." Journal of the American Academy of Child and Adolescent Psychiatry43, no. 3. (March 2001): 347.

Gansler, David A. "Hypoperfusion of inferior frontal brain regions in abstinent alcoholics: a pilot SPECT study." Journal of Studies on Alcohol61, no. 1 (January 2000):32.

Van Heertum, R. "Single photon emission, CT, and positron emission tomography in the evaluation of neurologic disease." Radiologic Clinics of North America39, no. 5 (September 2001).

Laith Farid Gulli, M.D. Alfredo Mori, M.D. Jean Suvan, B.Sc., R.D.H.