Radium-226

radium seedsRadium-226 - UW-L Brachy Course Radium-226 - UW-L Brachy Coursethe Curies discover radium
The Curies discover radium in their laboratory



Relevant historical data: Radium was discovered by Marie Sklodowska-Curie and her husband Pierre in 1898 in the Czech Republic. While studying pitchblende, the Curies removed uranium and found the remaining material was still radioactive. In 1902, radium was isolated as a pure metal by Andre-Louis Debierne and Curie through the electrolysis of a pure radium chloride solution with a mercury cathode and distillation in hydrogen gas. Radium was formerly used in paint for watches, nuclear panels, aircraft switches, clocks and instrument dials, foods for a preservative and taste, and also in products such as toothpaste and hair cream.
Chemical/Radioactive Composition: alkaline earth metal, radium combines with most non-metals such as flourine, chlorine, nitrogen and oxygen and radium reacts with acids producing hydrogen gas. Atomic Number=88, Relative Atomic Mass=226.02
Energy Characteristics: Alpha 4.78 MeV (94.5%) , Alpha 4.61 MeV (5.55%), Gamma 0.186 MeV (3.5%) Eave 0.83 MeV Specific Activity (Ci/g)=1.0
Exposure Rate Constant: 8.25 R-cm^2/mg-h(0.5 mm Pt filtration) 9.09 R-cm^2/mg-h(0.0 mm Pt filtration) 6.84 R-cm^2/mg-h(2.0 mm Pt filtration)
Half-life Properties: 1602 years Radium-226 is a radioactive decay product in the uranium-238 decay series and is the precursor of radon-222 ( Ra----------->Rn + He)
Forms available for use: The only radium that has any commercial applications is radium-226.
HVL in lead: 12mm HVL in lead TVL 30mm
Measurement/Calibrations/QA: the SI unit of radioativity is the becquerel, equal to one disintegration per second. The curie is a non-SI unit defined as the amount of radioactivity which has the same disintegration rate as 1 gram of Ra-226 (3.7x10^10 disintegrations per second or 37 GBq)
Used in formula/calculation: Activity expressed as milligram radium equivalent (mgRaeq)-1 mg of radium=8.25 R/hr at 1 cm distance when enclosed within a 0.5mm pt wall
calculation example:
exposure rate constant for Cesium is 3.26 R-cm^2 /mCi-h
exposure rate constant for Radium is 8.25 R-cm^2/mg-h
the conversion factor is 8.25/3.26=2.53 mCi of Cesium/mg of Radium
Uses in Radiation Oncology: used for short distance radiotherapy as implants using Gamma rays rather than Alpha. Supplied mostly in the form of radium sulfate or radium chloride which is mixed with an inert filler and loaded into gold cells. The cells are loaded into a platinum sheath which is also sealed. These sources are manuafactured as needles (Uniform, Indian Club, Dumbbell) or tubes in a variety of activities and lengths. Cancer of the uterine body can be treated with radium using Heyman capsules. These are available in different sizes, each containing 5 to 10 mg Radium. The uterine cervix may be treated with radium in the tandem and ovoid application with the dose specification also in milligram-hours.(man made isotopes have replaced the use of radium in mainstream medicine)
Treatment Planning: Radium is encapsulated and sealed in needles or tubes to prevent the escape of radium or its decay products and is inserted directly into tumors and tissues. The average energy of the gamma ray that a sealed Ra-226 source emits is 1.2 MeV. The Heyman technique for gynecologic applications consists of packing the uterine cavity with multiple radium sources. Dose to the inside surface of the uterine cavity is given in terms of milligram-hours. The Manchester system for treating the cervix is based on four points: A, B, bladder and rectum. The duration of the implant is based on dose calculated at point A which is defined at 2cm superior and 2cm lateral to the cervical os.The possibility of leaking and the increased availability of other less hazardous reactor produced isotopes such as Cesium has led to the gradual decline in the use of radium for brachytherapy.(Radium sources encapsulated in platinum can remain sealed safely for more than 400 years)
One other interesting fact: the name radium comes from the Latin word for ray,radius


Links:
radium





References:
"Radioactive Sources in Brachytherapy" by Janez Burger
Handbook of Radon
www.orau.org
Argonne National Laboratory, EVS Fact sheet August 2005
www.chemsoc.org
"Treatment Planning and Dose Calculation in Radiation Oncology" by Bentel
Wikipedia
Chemcal Elements: From Carbon to Krypton
Jefferson Lab Science Education
"The Physics of Radiation Therapy" by Faiz M. Khan
Lateral Science
chemicalelements.com
Washington State Department of Health-Office of Radiation Protection
Web-Based Dosimetry Training Tool

More pages