Unsealed source radiotherapy
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Overview
Unsealed source radiotherapy relates to the use of soluble forms of radioactive substances which are administered to the body by injection or ingestion. Such substances are typically used for their biological properties, which are similar to their non-radioactive parent substance.
A review of the subject was published in 1999 by Wynn A. Volkert and Timothy J. Hoffman.[1]
For example, iodine is an element selectively taken up by the thyroid gland in healthy people. Thyroid disease (both benign conditions like thyrotoxicosis and malignant conditions like papillary thyroid cancer) can be treated with radioactive iodine (iodine-131) which is then concentrated into the thyroid. Iodine-131 produces beta and gamma radiation. The beta radiation released destroys thyroid tissue, and any thyroid cancer that takes up iodine whilst most of the gamma radiation escapes the patient's body.
Most of the iodine not taken up by thyroid tissue is excreted through the kidneys into the urine. After radioactive iodine treatment, the urine will be radioactive or 'hot', and the patients themselves will also be radioactive. Depending on the amount of radioactivity administered, it can take days to weeks for the radioactivity to reduce to the point where the patient is not a radiation danger to bystanders. There are strict radiation protection regulations governing the use of these sources.
Other unsealed sources include:
- I-131-MIBG (metaiodobenzylguanidine) for the treatment of phaeochromocytoma and neuroblastoma
- P-32 for overactive bone marrow (the main place of use of phosphorus is the bone marrow)
- Sr-89 & Sm for secondary cancer in the bones (strontium and samarium behave just like calcium)
- Y-90 (yttrium) for radiosynovectomy in the knee joint
Radium-226 and caesium-137 are two classic examples of isotopes which are unsuitable for use in this type of radiotherapy.
- Radium has a very long physical halflife and chemically it behaves like calcium and so is concentrated in bones.[1] It will remain within the body far too long and it would continue to irradate the bone marrow for the rest of the life of any patient.
- Caesium acts like potassium and enters all the cells of the body, thus it does not concentrate in a single organ. As a result it is not possible to deliver a high dose to a single part of the body using cs-137. Cesium has a biological halflife of between one and four months in humans.
- Experimental antibody based methods - alpha emitters
At the ITU work is being done on Alpha-Immunotherapy, this is an experimental method where antibodies bearing alpha isotopes. Bismuth-213 is one of the isotopes which has been used. This is made by the alpha decay of Ac-225. The generation of one shortlived isotope from longer lived isotope is a useful method of providing a portable supply of a shortlived isotope. This is similar to the generation of technetium-99m by a technetium cow. The actinium-225 is made by the irradiation of radium-226 with a cyclotron.
Notes:
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
