Isotope study

• Through a needle into a vein (usually the inside of the elbow).
• Through a catheter, that is inserted into a vein or artery and is then guided to the organ being tested.
• Ingestion (for example, to test the thyroid, the patient drinks radioactive iodine).

When the isotope has had sufficient time to be absorbed by the organ, the patient is placed on a table (called a gantry) under the scanner. This may be a rectilinear scanner or gamma camera (devices which detect the gamma rays that are emitted by the isotope). The patient is required to remain still to produce an accurate image. The camera then transmits the information to a computer, which displays an image of that organ or region. A "picture" can be reproduced onto an X-ray film, and a computer printout is usually generated. For some tests, a counter is placed over the organ, and the amount of radioactivity or intensity of radioactivity is recorded.

A technician interprets the information as it is transmitted to the computer and can guide the camera to specific locations to get a better image.

How to Prepare:
You must sign a consent form.
Fast overnight before the test. Depending on the region being scanned, you may need to wear a hospital gown. Remove jewelry, dentures, and other metal that may affect the scan.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How it Feels:
If the isotope is injected, there will be a sharp prick when the needle is inserted. If a catheter is inserted, the site of insertion is usually numbed with an anesthetic. You will first feel a prick when the needle is inserted but will feel little more than slight pressure or tugging during the injection of the isotope. If the isotope is ingested, the flavor of the liquid may be unpleasant, but no pain is involved.

For patients who are extremely sensitive to the isotope, there may be nausea , headache , or vomiting . Discuss allergies with the health care provider or technician before the test.

Risks:
Generally, the risks involved with this type of study are similar to those of X-rays (radiation) and blood tests (injection).

For radiation, the greatest concern is with pregnant or nursing women. Infants and fetuses are more sensitive to the effects of radiation because they are still growing. The higher the dose of radiation and the number of exposures to radiation increase the risk. Generally, a few X-rays for diagnostic purposes (dental, chest, extremities) are not considered dangerous.

See the specific type of scan for other information.

Why this Test is Performed:
This test shows the size, shape, position, and some functions of an organ. If another test has indicated cancer or other abscesses , this test can help support that diagnosis. If other tests show cancer or infection, this test can indicate the location. Therapy can be monitored and evaluated.

Normal Values:
Most organs and bones absorb the isotopes uniformly.

Abnormal Results:

• abnormal size, shape, or position of an organ
• change in organ function
• stones
• cancer
• arthritis
• bone fractures
• acute infection
• growths
• abscesses
• embolism
• cysts
• intrauterine bleeding
• spinal fluid leak
• spleen injury
• swelling of the testicles
• blood clots

Additional conditions under which the test may be performed:

• anaplastic carcinoma of the thyroid
• autonomic neuropathy
• gastroparesis
• Huntington's disease
• unilateral hydronephrosis

Cost:
Isotope studies vary greatly in cost depending on the organ being tested, which isotope is used, and whether any special equipment is needed.

A simple thyroid scan or renal scan could range from $100 to $200. Most internal organ scans are about $250 to $350, with bone scan and cardiac scans (see Nuclear ventriculography (MUGA or RNV) ) costing up to $600. The hospital, technician, or other considerations (such as special computer equipment and the length of the hospital stay) will be added to that amount.

Special Considerations:
The reason for conducting an isotope study usually outweighs the concerns about radiation or other minor reactions.


This special scan (scintiscan) shows enlargement of the thyroid gland and extension behind the breastbone (retrosternal space). The false color image was generated by a computer during a radioisotope (I-131) thyroid scan.