Actinium-225
Decay mode Decay energy (MeV) | | |
α | 5.9351 | |
---|---|---|
Isotopes of actinium Complete table of nuclides |
Actinium-225 (225Ac, Ac-225) is an
The decay properties of actinium-225 are favorable for usage in
Decay and occurrence
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Decay_Chain%284n%2B1%2C_Neptunium_Series%29.svg/230px-Decay_Chain%284n%2B1%2C_Neptunium_Series%29.svg.png)
Actinium-225 has a half-life of 10 days and decays by
As a member of the neptunium series, it does not occur in nature except as a product of trace quantities of 237Np and its daughters formed by
Discovery
Actinium-225 was discovered in 1947 as part of the hitherto unknown neptunium series, which was populated by the synthesis of 233U.[3] A team of physicists from Argonne National Laboratory led by F. Hagemann initially reported the discovery of 225Ac and identified its 10-day half-life.[4] Independently, a Canadian group led by A. C. English identified the same decay scheme; both papers were published in the same issue of Physical Review.[3][5][6]
Production
As 225Ac does not occur in any appreciable quantities in nature, it must be synthesized in specialized nuclear reactors. The majority of 225Ac results from the alpha decay of 229Th, but this supply is limited because the decay of 229Th (half-life 7340 years) is relatively slow due to its relatively long half-life.[7] It is also possible to breed 225Ac from radium-226 in the 226Ra(p,2n) reaction. The potential to populate 225Ac using a 226Ra target was first demonstrated in 2005, though the production and handling of 226Ra are difficult because of the respective cost of extraction and hazards of decay products such as radon-222.[7]
Alternatively, 225Ac can be produced in
For decades, most 225Ac was produced in one facility—the Oak Ridge National Laboratory in Tennessee—further reducing this isotope's availability even with smaller contributions from other laboratories.[8] Additional 225Ac is now produced from 232Th at Los Alamos National Laboratory and Brookhaven National Laboratory.[10] The TRIUMF facility and Canadian Nuclear Laboratories have formed a strategic partnership around the commercial production of actinium-225.[11]
The low supply of 225Ac limits its use in research and cancer treatment. It is estimated that the current supply of 225Ac only allows about a thousand cancer treatments per year.[7][12]
Applications
Alpha emitters such as actinium-225 are favored in cancer treatment because of the short range (a few cell diameters) of alpha particles in tissue and their high energy, rendering them highly effective in targeting and killing cancer cells—specifically, alpha particles are more effective at breaking DNA strands. The 10-day half-life of 225Ac is long enough to facilitate treatment, but short enough that little remains in the body months after treatment.[10] This contrasts with the similarly investigated 213Bi, whose 46-minute half-life necessitates in situ generation and immediate use. Additionally, 225Ac has a median lethal dose several orders of magnitude greater than 213Bi because of its longer half-life and subsequent alpha emissions from its decay products. Each decay of 225Ac to 209Bi nets four high-energy alpha particles, greatly increasing its potency.[10][13]
Despite its limited availability, several clinical trials have been completed, demonstrating the effectiveness of 225Ac in targeted alpha therapy.
See also
References
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- ^ .
- ^ LCCN 2016935977.
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- .
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- ^ PMID 29658444.
- ^ U.S. Department of Energy (2018). "How scientists discovered a new way to produce actinium-225, a rare medical isotope". Phys.org. Retrieved 8 November 2019.
- PMID 27776333.
- ^ 1663. No. March 2016. Los Alamos National Laboratory. pp. 27–29.
- ^ "TRIUMF and CNL to form strategic partnership to enable ground-breaking cancer treatment". TRIUMF. 27 September 2018.
- ^ UBC Science (2019). "Accelerating access to an elusive medical isotope". Medium. Retrieved 8 November 2019.
- ^ PMID 22202153.