Which of the following elements is obsolete in radiotherapy:
Radium 226 Abeloff's Clinical Oncology writes-"Radium was the most impoant implantation source used for more than 5 decades in the twentieth century. However, many propeies of radium make it undesirable as a radioactive source for therapy. During its decay, radium produces radon gas, which is colorless and odorless but highly radioactive. Moreover, radium has a very long half-life (1620 yrs.!!). These qualities make it a significant hazard in the case of contamination. Hence, more suitable isotopes have replaced radium in clinical applications. Cesium-137 is widely used for gynecologic brachytherapy implants. It has a lower-energy gamma ray than radium (i.e., it is less penetrating and easier to shield), and it has no gaseous daughter nuclei. Palladium-103, iridium-192, and iodine-125 are used for implantation in the body for brachytherapy treatments.............................................................................. Today, cobalt 60 is used primarily for palliative teletherapy or for stereotactic teletherapy to small malignant lesions in the brain and benign lesions such as acoustic neuromas or aeriovenous malformations."
Radium 226
Cobalt 60
Iridium 192
Cesium 137