R – distance (in centimetres) from the centre of the active source to the point of interest, 137Cs, 192Ir and 60Co would be suitable candidates, because all of them emit relatively high-energy photons. Sources adequate for intracavitary applications should have radial dose functions which do not fall rapidly with distance. In general, intracavitary irradiation requires more penetration in tissue than interstitial brachytherapy. The thickness of any materials that reduce the exposure by 50% is known as the half-value layer (HVL). When high-energy sources, such as 198Au, are used, the patient needs to stay in the hospital until the source strength decays to a suitable value, such that the radiation exposure outside the patient satisfies state regulations. Low-energy photon emitting sources, such as 125I and 103Pd, are often used for permanent brachytherapy treatments, because the radiation of these sources is mostly diminished by the patient's tissue. High energy sources allow a higher dose to tissues at larger distances to the sources, but require thicker shielding for protection of the staff. The average energy of a brachytherapy source determines the penetrability of the photon particles emitted from the source. Especially in developing countries frequent source exchanges may be challenging in view of the available infrastructure. Typical intervals for source replacements foresee 25 source exchanges for 192Ir compared to just a single one for 60Co, resulting in reduced operating costs as a result of a longer half-life, 5.3 years ( 60Co) compared to 74 days ( 192Ir). These two radionuclides show different physical characteristics, while 60Co offers logistical and economic advantages. Recently 60Co sources became available with identical geometrical dimensions as miniaturized 192Ir sources. This made 192Ir the most used isotope for HDR afterloading brachytherapy worldwide. The smaller size of the sources allowed interstitial treatment and optimization of dose. Up to now the production of small sources for HDR afterloading was only possible for iridium-192, because of technological reasons. It has proven to be a successful treatment for cancers of the prostate, cervix, endometrium, breast, skin, bronchus, oesophagus, head and neck and several other types of cancer. The use of high-dose-rate (HDR) afterloading brachytherapy is a highly widespread practice today. 74 days), making it an interesting alternative especially in developing countries. Nevertheless, there are potential logistical advantages of 60Co sources due to its longer half-life (5.3 years vs. The results of this work show that no advantages or disadvantages exist for 60Co sources compared to 192Ir sources with regard to clinical aspects. The motivation is to provide useful information to support decision-making procedures in the selection of equipment for brachytherapy treatment rooms. The purpose of this work is to investigate the advantages or disadvantages of both radionuclides for HDR brachytherapy due to their physical differences. In an additional part of this paper reports from medical physicists of several radiation therapy institutes are discussed. This paper compares the characteristics of both nuclides in different fields of brachytherapy based on scientific literature. Recently also 60Co sources have been made available with identical geometrical dimensions. The smaller size of 192Ir sources made it the preferred radionuclide for temporary brachytherapy treatments. This paper compares the isotopes 60Co and 192Ir as radiation sources for high-dose-rate (HDR) afterloading brachytherapy.

Disadvantages of using cobalt 60