brain scan (Cisternogram, Cerebral blood flow, DaT scan)
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p176-177
2025-10-30
58
Type of test Nuclear scan
Normal findings
No areas of altered radionuclide uptake within the brain
Test explanation and related physiology
The usefulness of a nuclear brain scan is narrow compared with computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans of the brain. Primarily, a nuclear brain scan is used to indicate complete and irreversible cessation of brain function (brain death). This determination, when combined with appropriate clinical data, allows for cessation of medical therapy and opportunity for the harvest of potential donor organs. With brain death, there is complete absence of blood perfusion to the brain.
The brain scan can also be used to indicate cerebral vascular occlusion or stenosis. With the use of Diamox (acetazolamide), an accurate assessment of local cerebral blood flow can be determined. Diamox is a carbonic anhydrase inhibitor that results in the elevation of Pco2 in the bloodstream. Normally, this causes dilatation of the cerebral blood vessels. If asymmetric blood flow is noted after Diamox injection, cerebral vascular occlusion or stenosis can be suspected.
Brain scans are also used to investigate the ventricular system (cisternogram) of the central nervous system. Normal pressure hydrocephalus and ventricular shunt dysfunction can be identified and located.
Contraindications
• Patients who are pregnant unless the benefits outweigh the risk of fetal damage
• Patients who cannot cooperate during the testing
Interfering factors
* Many sedative drugs can affect brain nuclear imaging.
* Angiotensin-converting enzyme (ACE) inhibitors, vasoconstrictors, and vasodilators can alter blood flow distribution in nuclear brain imaging.
Procedure and patient care
Before
* Explain the procedure to the patient.
• Administer blocking agents as ordered before scanning.
• Consider having a sedative ordered for agitated patients.
During
• Note the following procedural steps:
1. After administration of the radioisotope, the patient is placed in the supine position while planar and single- photon emission computed tomography (SPECT) images are obtained.
2. When cerebral flow studies are performed, the counter is immediately placed over the head.
3. The counts are anatomically recorded in timed sequence to follow the isotope during its first flow through the brain.
• Note that this study is performed by a technologist in the nuclear medicine department in approximately 35 to 45 minutes.
After
* Because only tracer doses of radioisotopes are used, inform the patient that no precautions need to be taken to prevent radioactive exposure to other personnel or family present.
* Encourage the patient to drink fluids to aid in the excretion of the isotope from the body.
Abnormal findings
- Cerebral death
- Cerebral vascular stenosis/occlusion
- Cerebral neoplasm
- CSF leakage
- Hydrocephalus
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