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Machines with Radionuclide Sources
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
John Saunders, Lee Walton, Katharine Hunt
Cobalt-60 is manufactured by irradiating cobalt-59 in a high-neutron-flux nuclear reactor. The main reasons for its suitability for teletherapy are the availability of relatively small, high-specific-activity sources that minimise the beam penumbra; its relatively long half-life (5.27 years); and the almost monochromatic high-energy photon emission (photons of 1.173 MeV and 1.333 MeV in equal quantity).
Radiation Therapy and Radiation Safety in Medicine
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
IMRT's rapid implementation does have its detractors, who argue that the adoption of this technology has been driven by hospitals competing for patients and higher insurance reimbursements, ahead of clinical studies of its effectiveness.* Others worry that because IMRT uses a higher intensity that it also can entail a greater radiation risk without proven benefits. It is hoped that ongoing clinical trials of IMRT will address these critiques. One of the challenges is the radiation dose and beam-range uncertainty, which is due to the uncontrolled motion of internal organs caused in part by breathing, digestion and heartbeats. The research to evaluate and reduce the impact of such effects is ongoing (Uchinami, Y. et al., “Impact of organ motion on volumetric and dosimetric parameters in stomach lymphomas treated with intensity-modulated radiotherapy” J. Appl. Clin. Med. Phys., Vol. 20, 2019, pp. 78–86.). The high expense of any accelerator-based technique leads to radioactive cobalt-60 sources being more practical for radiation therapy in the developing world.
The Effect of Dose Rate, Fractionation and Post-Irradiation Repair
Published in K. H. Chadwick, Understanding Radiation Biology, 2019
Edwards and Lloyd (1980) have also discussed the need for dose–effect curves to be measured using constant exposure times. However, their arguments are based on the Classical Theory of chromosomal aberration induction and are only applied to chromosomal aberration yields. Lloyd et al. (1984), subsequently, measured a series of dose–effect relationships for chromosome aberrations in non-cycling human lymphocytes, using constant irradiation times of 1, 3, 6 and 12 hours, to cobalt-60 gamma rays. An acute exposure to cobalt-60 gamma rays made some years prior to the constant time of exposure experiment was also used in the analysis. Precautions were taken to ensure that the unstimulated lymphocytes were metabolically active, maintained at a constant temperature during exposure and cultured using a standard procedure after exposure. Care was also taken to ensure that the radiation field remained constant during the experiment. Figure 5.7 presents the results for dicentric aberrations and for acentric aberrations using the parameters derived by Lloyd et al. (1984).
A comprehensive review on recent nanosystems for enhancing antifungal activity of fenticonazole nitrate from different routes of administration
Published in Drug Delivery, 2023
Sadek Ahmed, Maha M. Amin, Sinar Sayed
This test is performed to ensure the ability of nanosystem to preserve its physical properties, measured responses and release profile following the sterilization process by gamma radiations. Gamma sterilization was performed in presence of dry ice to prevent any undesirable consequences. Cobalt-60 irradiator at rate of 1.774 kGy/h was employed with a radiation dose of 25 kGy in an Indian Gamma cell (Ahmed et al., 2022). Afterward, the resulted formulae were compared to the freshly prepared optimum formulae as previously discussed under effect of storage. Sterilization is important to eradicate any microbial contamination that could infect the body tissue especially the eye (Sayed et al., 2020). This test was performed for O-NV and O-OLN and both of them verified the absence of aggregates, unchanged responses (p > 0.05) and similar release profiles (ƒ2 > 50) (Ahmed et al., 2022a,b).
Comparing Iridium-192 with Cobalt-60 sources in high-dose-rate brachytherapy boost for localized prostate cancer
Published in Acta Oncologica, 2022
Jörg Tamihardja, Stefan Weick, Paul Lutyj, Marcus Zimmermann, Klaus Bratengeier, Michael Flentje, Bülent Polat
High-dose-rate brachytherapy (HDR-BT) in combination with external beam radiotherapy (EBRT) is an established treatment option for localized prostate cancer. Due to the small size of the sources, Iridium-192 (Ir-192) is often preferentially utilized in interstitial HDR-BT. Since Cobalt-60 (Co-60) sources with identical dimensions to those of Ir-192 have been made available, its physical properties make the radionuclide Co-60 an interesting alternative in clinical brachytherapy [1–3]. Co-60 has a longer half-life compared to Ir-192 with 63.3 months versus 2.4 months leading to a reduced number of source exchanges and therefore a significant cost reduction. As a tradeoff, Co-60 has a higher mean energy with 1.25 MeV compared to 0.37 MeV for Ir-192 resulting in the need for increased machine and room shielding. Moreover, Co-60 has a lower equivalent dose rate in air by a factor of 2.8 resulting in increased treatment times and the higher mean energy of Co-60 raises the concern about possible increased toxicity compared to patients treated with Ir-192. Therefore, in this current publication, the long-term oncological outcome, gastrointestinal (GI) and genitourinary (GU) toxicity, and dosimetric properties of two large real-life cohorts of prostate cancer patients treated with Ir-192 or Co-60 HDR-BT boost are compared.
Radiobiological and social considerations following a radiological terrorist attack; mechanisms, detection and mitigation: review of new research developments
Published in International Journal of Radiation Biology, 2022
Tanya Kugathasan, Carmel Mothersill
Nuclear technology is actively being innovated improperly with the use of stolen radioactive sources. Many terrorists retrieve radioactive sources from improperly secured nuclear weapons, nuclear power facilities, or material from radiation therapy (Gale and Armitage 2018). Radioactive sources have also been proven to be found on the black market (Rump et al. 2021). Most radiotherapy sources and devices are monitored by the International Atomic Energy Agency (IAEA) on an online voluntary database. This database is called the Directory of Radiotherapy Centers (DIRAC) database (Coleman et al. 2017). Although it monitors most radioactive sources, it does not account for any stolen sources and so there lies some inaccuracy in the database. It was stated by Coleman et al. (2017) that at least 86 Cobalt-60 medical devices were found in Africa. 75% of devices are in 7 countries: South Africa, Morocco, Tunisia, Algeria, Egypt, Nigeria, and Sudan. The other 25% is found in 16 other countries.