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Radium - 226
. Photos:
Image 1. Natural cycle of Radium-226. (4)
Image 2. Radium 226 decay (9)
Marie and Pierre Curie Research (13)
Links:
Wikipedia. http://en.wikipedia.org/wiki/Radium
Jefferson Lab. http://education.jlab.org/itselemental/ele088.html
United States Environmental Protection Agency. http://www.epa.gov/rpdweb00/radionuclides/radium.html#use
Gamma Dating Center. http://geo.ku.dk/english/gdc/
Radium Deacy. http://langitselatan.com/2008/01/23/begini-cara-kerja-bintang-bagian-2-sumber-energi-bintang/
Proposed Regulation... http://www.leg.state.nv.us/Register/2008Register/R185-08P.pdf
National Science Foundation. http://www.atomicarchive.com/Bios/CuriePhoto.shtml
References:
1. Wikipedia. http://en.wikipedia.org/wiki/Radium. Accessed March 16, 2009.
2. Jefferson Lab. http://education.jlab.org/itselemental/ele088.html Accessed March 16, 2009.
3. United States Environmental Protection Agency http://www.epa.gov/rpdweb00/radionuclides/radium.html#use Accessed March 16, 2009.
4. Gamma Dating Center. http://geo.ku.dk/english/gdc/ Accessed March 16, 2009.
5. Bentel, Gunilla C. Radiation Therapy Planning. 2nd Edition. McGraw-Hill Companies Inc.; 1996: 533-561.
6. Khan, Faiz M. The Physics of Radiation Therapy. 3rd Edition. Philadelphia: Lippincott Williams & Wilkins; 2003: 357-400.
7. Khan, Faiz M. Treatment Planning in Radiation Oncology. 2nd Edition. Philadelphia: Lippincott Williams & Wilkins; 2007: 212-257.
8. Session: 7.4 – Sources for Temporary Implants. Web-Based Dosimetry Training Tool. Retrieved March 16, 2009. Available at:http://www.dosimetrytrainingtool.com
9. Radium Deacy. Available at:http://langitselatan.com/2008/01/23/begini-cara-kerja-bintang-bagian-2-sumber-energi-bintang/. Accessed March 18, 2009.
10. DTT, Module 07.02-Dosimetric Parameters Used for the Characterization of Brachytherapy Sources. Accessed March 23, 2009, Stanford Web-Based Dosimetry Training Tool. Available at http:// www.dosimetrytrainingtool.com
11. Proposed Regulation of the State Board of Health LCB radium-226 and americium-241; adopting by reference certain federal regulations; ... of the filter paper after the dry wipe test must be measured by a ...Accessed March 23, 2009. Available at www.leg.state.nv.us/Register/2008Register/R185-08P.pdf
12. Podgoršak, Ervin. Radiation Physics for Medical Physicists. Birkhauser Publishing; 2006: 319-320.
13. National Science Foundation. Marie and Pierre Curie. Accessed April 8, 2009. Available at: http://www.atomicarchive.com/Bios/CuriePhoto.shtml
Group Colors:
Jen
Lindsey
Dawn
Robin
Image 1. Natural cycle of Radium-226. (4)
Image 2. Radium 226 decay (9)
Marie and Pierre Curie Research (13)
| Relevant Historical Data: | Radium 226 is a naturally occurring radionuclide that was discovered in 1898 by Marie and Pierre Curie along with Henri Becquerel when they isolated it from Uranium pitch blende ore. (8) Radium 226 was one of the first radionuclides utilized for clinical brachytherapy applications and was the radionuclide of choice in the early days of development of brachytherapy. (8) Radium 226, the earliest and once most commonly used radioactive isotope in brachytherapy, has been replaced by artificially produced isotopes such as Cs-137 and Ir-192. (5)(8) Radium 226 was originally used to define the unit Curie (Ci) with 1 Ci being the number of disintegrations of a 1g radium source. (8) |
| Chemical/Radioactive Composition: | Chemical Symbol: Ra Atomic number (Z, # of protons) = 88 Mass number (A, # of protons + neutrons) = 226 Radium 226 is the sixth member of the uranium series which begins with U-238 and ends with Pb-206. (8) Radium is supplied mostly in the form of radium sulfate or radium chloride. It is then mixed with an inert filler and loaded into cells about 1cm long and 1mm in diameter. The cells are made of 0.1-0.2mm thick gold foil and are sealed to prevent leakage of radon gas. They are then loaded into a sealed platinum sheath. (6) Radium 226 disintegrates very slowly to form radon, a hazardous radioactive gas. (5) When radium is placed in a sealed container it achieves secular equilibrium with its daughter products approximately one month from the time of encapsulation. (6) |
| Energy Characteristics: | At the end of the decay process from radium to stable lead at least 49 gamma rays are produced with energies ranging from 0.047 to 2.45 MeV. (6)(8) The average energy of the gamma rays from radium 226 in equilibrium with its daughter products and filtered by 0.5mm of platinum is 0.83 MeV. (6) Beta particles, ranging in energy from 0.017 MeV-3.3 MeV, are also emitted in the disintegration of Ra-226 to stable Pb-208. (8) Gamma rays are the only rays used for therapy, the alpha and most of the beta particles emitted are absorbed by the 0.5mm platinum source case. (6) |
| Exposure Rate Constant: | 8.25 Rcm2/mCi-h (when filtered by 0.5mm Pt or when in equilibrium with its daughter products) (6) The exposure rate constant decreases by about 2% for each additional 0.1 mm of Pt added to the 0.5 mm Pt encapsulation and increases by 2% for each 0.1 mm of Pt less than 0.5 mm. (8) |
| Half-life Properties: |
|
| Forms available for use: | Despite double encapsulation, the risk of radium escaping from the source poses a very seriuos risk. This, in addition to the fact that the availability of reactor produced isotopes has increased, had led to the decline of radium in brachytherapy cases. (5) |
| HVL in lead: | HVL in lead varies from .5mm for a 100 kev source to 12mm for cobalt (1) Because of its relatively high energy (2.45 MeV) Radium 226 has the highest half value layer (HVL) in lead of any brachytherapy source, ranging from 12mm-16mm. (6)(7)(8) |
| Measurement/Calibrations/QA: | Measurements Even though Radium 226 is no longer used in the field of radiation therapy there are other isotopes that are used in its place that are less toxic. Radium 226, however, set the basis for the measurement of other isotopes that we currently use today. For instance, milligram radium equivalent is the unit used for specifying the source of photon-emitting brachytherapy. It is the amount of Ra 226 filtered by .5 mm thick of Pt that produces the same exposure rate at 1 meter in air as that of the given source. (10) Calibrations The National Institute of Standards and Technology (NIST) have established exposure rate calibration standards for Radium 226. The NIST method consists of calibrating a working standard of each type using open-air geometry and a series of spherical graphite cavity chambers. A given source is then calibrated by intercomparison with the working standard using a 2.5-liter spherical aluminum ionization chamber, positioned at a distance of about 1 m. A similar procedure is used for calibrating a radium source except that the working standards of radium have been calibrated in terms of actual mass of radium. Calibrations of clinical sources should be directly traceable to the NIST or one of the AAPM-ADCLs. This means that the sources are calibrated by direct comparison with a NIST or ADCL calibrated source of the same kind, same radionuclide, same encapsulation, size and shape. If a well-type ionization chamber is used, it should bear a calibration factor determined with a NIST or ADCL calibrate source of the same kind.(6) Quality Assurance Testing It is very important that an acceptance test be performed prior to the use of the source. The purpose of acceptance testing of brachytherapy equipment is to ensure that the source and the associated equipment meet the user’s specifications. A wipe test must be performed at the time of acceptance and every 6 months to verify that everything is correct. Also the physical length, serial number and color-coding of all sources should be checked. Documentation of the source use, strength, removal of the sources from storage and the actual return of source is very important for the accuracy and integrity of the program. Geiger Muller counters and other surveyors would be needed to track the isotope if any were to be misplaced and to take a reading of the patient. (11) |
| Used in formula/calculation: | What is the activity of 1 g of Ra226? Half life is 1,622 years Λ=.693/T ½ = 0.693 (1,622 years) (3.15 x 10 ^7 sec/year) =1.356 x 10^ -11/sec Activity= 2.66 x 10^21 x 1.356 x 10^-11 dps/g =3.61 x 10^10 dps/g =.975Ci/g (6) |
| Uses in Radiation Oncology: | In the U.S., nasal radium irradiation was administered to children to prevent middle ear problems or enlarged tonsils from the late 1940s through early 1970s. Radium (usually in the form of radium chloride) is used in medicine to produce radon gas which in turn is used as a cancer treatment. The isotope 223Ra is currently under investigation for use in medicine as cancer treatment of bone metastases. (1) |
| Treatment Planning: | Historically, the external use of radium was focused on the treatment of malignant disease. Internal use of radium-226 occurred between 1905-1930 through ingestion of soluble radium salts. Before the advent of cobalt and cesium teletherapy machines in the 1950s, all external beam radiotherapy machines made use of radium-226 ("teleradium machines"). With the invention of the Cobalt teletherapy machine, teleradium machines were no longer used. Although, radium still proved to be effective for brachytherapy procedures by inserting it into body cavities or tumors for a specified period of time. Radium's use in brachytherapy was discontinued because of the health risks of its daughter product Radon-222, its high cost for extraction, and its low specific activity compared to other safer, cheaper, isotopes. (12) |
| One other interesting fact: | Radium is about one million times more active than uranium. The lab notebooks used by the Curies are too highly contaminated to be safely handled today. (2) Radium has been added to the tips of lightening rods, improving their effectiveness by ionizing the air around it. (3) |
Links:
Wikipedia. http://en.wikipedia.org/wiki/Radium
Jefferson Lab. http://education.jlab.org/itselemental/ele088.html
United States Environmental Protection Agency. http://www.epa.gov/rpdweb00/radionuclides/radium.html#use
Gamma Dating Center. http://geo.ku.dk/english/gdc/
Radium Deacy. http://langitselatan.com/2008/01/23/begini-cara-kerja-bintang-bagian-2-sumber-energi-bintang/
Proposed Regulation... http://www.leg.state.nv.us/Register/2008Register/R185-08P.pdf
National Science Foundation. http://www.atomicarchive.com/Bios/CuriePhoto.shtml
References:
1. Wikipedia. http://en.wikipedia.org/wiki/Radium. Accessed March 16, 2009.
2. Jefferson Lab. http://education.jlab.org/itselemental/ele088.html Accessed March 16, 2009.
3. United States Environmental Protection Agency http://www.epa.gov/rpdweb00/radionuclides/radium.html#use Accessed March 16, 2009.
4. Gamma Dating Center. http://geo.ku.dk/english/gdc/ Accessed March 16, 2009.
5. Bentel, Gunilla C. Radiation Therapy Planning. 2nd Edition. McGraw-Hill Companies Inc.; 1996: 533-561.
6. Khan, Faiz M. The Physics of Radiation Therapy. 3rd Edition. Philadelphia: Lippincott Williams & Wilkins; 2003: 357-400.
7. Khan, Faiz M. Treatment Planning in Radiation Oncology. 2nd Edition. Philadelphia: Lippincott Williams & Wilkins; 2007: 212-257.
8. Session: 7.4 – Sources for Temporary Implants. Web-Based Dosimetry Training Tool. Retrieved March 16, 2009. Available at:http://www.dosimetrytrainingtool.com
9. Radium Deacy. Available at:http://langitselatan.com/2008/01/23/begini-cara-kerja-bintang-bagian-2-sumber-energi-bintang/. Accessed March 18, 2009.
10. DTT, Module 07.02-Dosimetric Parameters Used for the Characterization of Brachytherapy Sources. Accessed March 23, 2009, Stanford Web-Based Dosimetry Training Tool. Available at http:// www.dosimetrytrainingtool.com
11. Proposed Regulation of the State Board of Health LCB radium-226 and americium-241; adopting by reference certain federal regulations; ... of the filter paper after the dry wipe test must be measured by a ...Accessed March 23, 2009. Available at www.leg.state.nv.us/Register/2008Register/R185-08P.pdf
12. Podgoršak, Ervin. Radiation Physics for Medical Physicists. Birkhauser Publishing; 2006: 319-320.
13. National Science Foundation. Marie and Pierre Curie. Accessed April 8, 2009. Available at: http://www.atomicarchive.com/Bios/CuriePhoto.shtml
Group Colors:
Jen
Lindsey
Dawn
Robin
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