Norm of Brain Single-Photon Emission Computed Tomography (SPECT Scan)
Normal brain and structures.
Usage of Brain Single-Photon Emission Computed Tomography (SPECT Scan)
Evaluate AIDS, Alzheimer's disease, anoxia, cerebrovascular accident, head trauma, Parkinson's disease, mild brain injury, transient ischemic attack; helps differentiate type of dementia (Alzheimer's, focal, multi-infarct, diffuse) by allowing identification of pattern of cerebral ischemia; helps differentiate Parkinson's disease from dopa-responsive dystonia; allows identification of the focus of seizure activity. Used to scan for ectopic (nonpituitary) tumor when acromegaly is suspected. SPECT is used experimentally in psychiatry to identify patterns coinciding with individual disorders.
Description of Brain Single-Photon Emission Computed Tomography (SPECT Scan)
SPECT scan is a nuclear medicine procedure that gives clinical information about organ function (versus CT and radiography, which give information about anatomy). In this scan, a radiopharmaceutical selected for its absorptive properties is injected intravenously, crosses the blood-brain barrier, decomposes, and remains for several hours in the brain tissue, where its qualitative and quantitative distribution can be detected with the SPECT camera. The camera sends images to a computer that can reproduce visual images, or “slices,” of the brain along several planes. Advantages of SPECT imaging over older nuclear medicine scans are that it can identify patterns of dementia earlier in the process and allow for early intervention for potentially reversible types of dementia. This scan can be done in a three-dimensional format. In addition to imaging the brain, SPECT is used for many organs, with different radiopharmaceuticals selected, based on their absorptive properties for the organ being imaged. Newer equipment called “dual mode imaging” combines SPECT with structural imaging modalities such as Ultrafast CT or MRI for improved imaging results. See Dual modality imaging.
Professional Considerations of Brain Single-Photon Emission Computed Tomography (SPECT Scan)
Consent form IS required.
Allergic reaction to the radiopharmaceutical (itching, hives, rash, tight feeling in the throat, shortness of breath, anaphylaxis, death).
Inability to lie motionless during the scan; women who are breast-feeding; previous allergic reaction to the radiopharmaceutical agent.
During pregnancy, risks of cumulative radiation exposure to the fetus from this and other previous or future imaging studies must be weighed against the benefits of the procedure. Although formal limits for client exposure are relative to this risk:benefit comparison, the United States Nuclear Regulatory Commission requires that the cumulative dose equivalent to an embryo/ fetus from occupational exposure not exceed 0.5 rem (5 mSv). Radiation dosage to the fetus is proportional to the distance of the anatomy studied from the abdomen and decreases as pregnancy progresses. For pregnant clients, consult the radiologist/ radiology department to obtain estimated fetal radiation exposure from this procedure.
- Remove all metal objects from the client's clothes, hair, and body.
- See Client and Family Teaching.
- The client is transported to the nuclear medicine department, positioned supine on the scanning table, and left to rest quietly for approximately 10 minutes to allow the brain to reach a basal activity level.
- A radiopharmaceutical is injected intravenously and allowed to circulate and cross the blood-brain barrier.
- The SPECT scan is then taken while the client lies motionless, with open eyes.
- See Client and Family Teaching.
Client and Family Teaching
- Do not drink caffeine-containing beverages for 24 hours before the scan.
- It is important to lie motionless during this scan. If the client is confused, a family member familiar to the client may remain in the room to reassure the client during the scan.
- The scan takes about 30 minutes.
- For about 24 hours after the scan, meticulously wash your hands after urination to remove any radioactivity from contaminated urine.
Factors That Affect Results
- The presence of metal objects, such as metal eyeglasses, over the scanning area may block some views.
- Movement of the client during imaging obscures the clarity of the images.
- The radiopharmaceutical half-life is about 6 hours.