Radioactive iodine uptake test
| Radioactive iodine uptake test | |
|---|---|
| Diagnostics | |
 Thyroid scan with Iodine-123 for evaluation of hyperthyroidism. |
|
| ICD-9-CM | 92.01 |
| OPS-301 code | 3-701 |
The radioactive iodine uptake test, or RAIU test, is a type of scan used in the diagnosis of thyroid problems, particularly hyperthyroidism. It is entirely different from radioactive iodine therapy (RAI therapy), which uses much higher doses to destroy cancerous cells. The RAIU test is also used as a follow up to RAI therapy to verify that no thyroid cells survived, which could potentially still be cancerous.[1]
The patient swallows 100-200 microcuries of radioactive iodine (131I sodium iodide) in the form of capsule or fluid, and its absorption by the thyroid is studied after 6 hours and after 24 hours with the aid of a scintillation counter.[2]
The normal uptake is between 15 and 25 percent, but this may be forced down if, in the meantime, the patient has eaten foods high in iodine, such as dairy products and seafood.[3] Low uptake suggests thyroiditis, high uptake suggests Graves' disease, and unevenness in uptake suggests the presence of a nodule.[4]
The test is inappropriate for patients who are pregnant or breastfeeding.[4]
I-123 has a shorter half life than I-131 (a half day vs. 8.1 days), so use of I-123 exposes the body to less radiation, but at the expense of less time to evaluate delayed scan images.[5] Also, I-123 emits gamma radiation, while I-131 emits gamma and beta radiation.[6]
[edit] Additional images
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Thyroid scintigraphy
[edit] References
- ^ [1] ThyCa: Thyroid Cancer Survivors' Association, Inc.,Radioactive Iodine (RAI).
- ^ Balint Kacsoh. Endocrine physiology. McGraw-Hill, 2000. Page 321.
- ^ M. Sara Rosenthal. The Thyroid Sourcebook. McGraw-Hill, 2008. Page 140.
- ^ a b WebMD article on RAIU test.
- ^ Ain, Kenneth; Rosenthal, M. Sara (2010-08-19). The Complete Thyroid Book, Second Edition. McGraw-Hill Professional. pp. 57–. ISBN 9780071743488. http://books.google.com/books?id=TyN9y7ZlBVsC&pg=PT57. Retrieved 18 July 2011.
- ^ Pilling, Gwen (1999-06-24). Salters higher chemistry. Heinemann. pp. 132–. ISBN 9780435630980. http://books.google.com/books?id=RiM4plecZw0C&pg=PA132. Retrieved 18 July 2011.
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