Brain scanning is a nuclear study performed to assist in diagnosing abnormalities of the brain and cerebral blood flow that are characteristic of pathology. The radionuclide 99mTc is administered IV as technetium Tc 99m pertechnetate, which requires a delayed imaging, as technetium Tc 99m diethylenetriamine pentaacetic acid (technetium Tc 99m DTPA), or as technetium Tc 99m gluceptate, which allows earlier imaging and increased sensitivity.¹⁵ These substances do not cross the blood-brain barrier to enter the brain because this complex system prevents materials from being transported from the blood into the neural tissue. The presence of disease that can cause a breakdown or disruption in this protective barrier allows the radionuclide to cross into and become concentrated in the abnormal parts of the brain. Scanning provides the location, size, and shape of an abnormality. Newer lipid-soluble radionuclides that are able to cross an intact blood-brain barrier are now used to scan and study the distribution of a tracer dose to evaluate cerebral perfusion over a period of time. These newer materials allow imaging of the entire brain instead of areas involving pathology only.¹⁶

Brain scanning has generally been replaced by diagnostic studies such as MRI and CT scanning, neither of which requires the use of a radionuclide.

• Blood-brain barrier intact with no uptake in flow and static views revealed; no intracranial pathology indicating a demyelinating disease, infection or inflammatory disease, atherosclerosis or stenosis, hemorrhage, aneurysm, tumors, or arteriovenous (AV) malformation

• Inability of client to remain still during the procedure, especially if the client is a child
• Environmental stimuli such as noise or bright lights that can affect the distribution of the radionuclide used in PET or SPECT

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Indications

• Frequent headache, seizure activity, or neurosensory or neuromuscular complaints or symptoms of unknown etiology
• Determination of the cause of cerebrovascular disease with or without a stroke, such as atherosclerosis, thrombosis, hemorrhage, or stenosis revealed by decreased uptake of radionuclide
• Identification of sites of cerebral ischemia or infarction with known presence of atherosclerotic disease
• Detection of intracranial masses such as gliomas, meningiomas, neuromas, cystic lesions, pituitary adenoma, malignant primary or metastatic tumors revealed by an increased uptake and irregular distribution of the radionuclide
• Diagnosis of the cause of intracranial bleeding as in a ruptured aneurysm, subdural hematoma resulting from trauma, or an AV malformation
• Diagnosis of infectious diseases such as encephalitis and brain abscess
• Diagnosis of demyelinating diseases such as multiple sclerosis
• Determination of whether hydrocephalus in children is surgically treatable or evaluation of shunt patency postoperatively
• Visualization of suture lines in children
• Detection of cerebral edema, hematoma, or contusion after head trauma
• Diagnosis of neurological disorders with presenting deficits or symptoms as in dementia, epilepsy, Parkinson's disease, Huntington's chorea, and Alzheimer's diseases when studied by PET
• Evaluation of the effect of radiation or chemotherapy on malignant brain tumor
• Determination of brain death revealed by an absence of uptake in the sinus or brain vascular system

Contraindications

• Pregnancy, unless the benefits of performing the procedure greatly outweigh the risks to the fetus

[Section Outline]

• Indications
• Contraindications

Nursing Care Before the Procedure

Explain to the client:

• That the procedure takes about 1 hour unless delayed scanning is planned within hours, requiring the client to return to the department
• That a sedative can be administered before the study to promote relaxation
• That a minute amount of radioactive material will be administered by IV injection and that this does not cause harm to the client or those in contact with him or her
• That the radioactive material is excreted by the body, usually in the urine
• That scanning will take place immediately after the injection or at a later time, depending on the material used, with a machine that moves over the area to be examined
• That a medication to enhance scanning can be administered before the procedure
• That the only discomfort experienced is the injection of the radiopharmaceutical

Prepare for the procedure:

• Obtain a history to ascertain last menstrual period date and possible pregnancy in women of childbearing age, known and suspected cerebral disorders, allergy to iodine, assessment information of neurological system, tests and procedures conducted and results, or therapeutic interventions performed.
• Administer any ordered medications such as potassium iodine to block thyroid uptake of the radionuclide or potassium chloride to block choroid plexus uptake if a radionuclide other than 99mTc is used.¹⁷
• Have the client void before the study to prevent discomfort or interruption.

The client is placed on the examining table in a supine position. If the client is a young child and unable to lie still, a general anesthetic can be administered. The radiopharmaceutical is administered IV, and scanning is performed with the scanner moved back and forth over the head for immediate computer images. If a SPECT study is performed, the images are obtained with the client in a supine position and the scanner rotated around the head. The client is reminded to lie very still while the scanner is operating. Scanning can be delayed and performed 30 minutes after the injection, depending on the radionuclide used. The client's position is changed to lateral and prone to obtain anterior, lateral, and posterior projections. Blood pool images and flow studies through the arterial, venous, and capillary phases are anatomically displayed, based on counts determined from the radioactivity of the radionuclide. In some instances, initial normal scans can appear abnormal at a later time. Later delayed images are obtained in 3 to 4 hours in the anterior, posterior, lateral, and vertex positions with the head in flexion. These static views can reveal abnormally increased uptake in the cortex to identify pathological tissue.

Nursing Care After the Procedure

• Advise the client of the time to return for additional imaging, if appropriate.
• Inform the client that the radioactive substance is eliminated from the body within 6 to 24 hours and that fluid intake should be increased to encourage this process.
• Phlebitis: Note and report redness, pain, and swelling at the IV site. Elevate arm, and apply warm compress to the site.