Strontium-90/Yttrium-90



Y-90 sr-90sr-90

Left: Y-90
Middle: Sr-90 in uptake of tooth
Right: 1960: Mother testing son's milk for Sr-90. Nuclear weapon testing involved Sr-90 radioactivity





Relevant historical data: Sr-90 is produced through nuclear fission. Sr-90 decays to Y-90. Strontium is a mineral (strontianite) named after the Scottish village of Strontian. It was discovered in the lead mines in 1787. Strontium is the 15th most available element on earth.
Yttrium, named for a village in Sweeden was discovered by a Finnish chemist in 1794. It is found in almost all rare-earth minerals and in uranium ores, but is never found in nature as a free element.
Chemical/Radioactive Composition: Strontium: Chemical symbol: Sr
Sr-90, in its pure form is a soft, shiny silver metal, but quickly turns yellow when exposed to air.
Yttrium: Chemical symbol: Y
Energy Characteristics: Sr-90 is beta emitter: one of the highest beta emitters, 0.546 MeV (max)
y-90 is a beta and gamma emitter: beta energy of 2.28 MeV and gamma energy of 2.18 MeV
Exposure Rate Constant:
Half-life Properties: Sr-90 = 28.9yr, Y-90 = 64.8 hr
Forms available for use: Sr-90: cylindrical seeds, used for dose delivery after stent placement in the heart to retard stenosis reformation
Y-90: liquid used for lymphoma salvage, Zevalin monoclonal antibody
HVL in lead: Sr-90 = 0.66 mm; Y-90 = 7.5 mm
note: these values are calculated and nolt defices as found in print. bear in mind that these isotopes are mostly beta emitters, therefore the most commonly used material for shielding is acrylic.
Measurement/Calibration/QA:
Used in formula/calculation:
Uses in Radiation Oncology: Sr-90 - because it is a beta emitter, it is used for superficial applications (in the treatment of pterygium) . SIDE NOTE: Sr-89 IS USED FOR TREATMENT OF BONE LESIONS BECAUSE OF THE SUBSTITUTES FOR CALCIUM IN BONE, WHERE CALCIUM TURNOVER IS GREATEST.
Treatment Planning: Mird method
One other interesting fact: Sr-90 contaminated a large area at the 1986 Chernobyl nuclear accident.
Sr-90 was among the radioactive materials released by the 1957 Windscale fire. (Windscale fire was considered the worlds worst reactor accident until the TMI incident in 1979. Both incidents were dwarfed by the Chernobyl disaster in 1986.
Strontium releases a large amount of heat during decay, therefore, is used in nuclear reactors.
Yttrium oxide (not Y-90) is used to stabilize the cubic form of zirconia, used in jewelry.


Links: www.bt.cdc.gov/radiation/isotopes/strontium.asp
www.wikipedia.org/wiki/strontium
www.wikipedia.org/wiki/yttrium




References: Physics in Nuclear Medicine, Sorensen & Phelps, 3rd edition

The physics of Radiation Therapy, Khan

More pages