Isotope (s) used in high dose rate brachytherapy – a) lr192b) Co–60c) Cs–l33d) Ra 226 e) Pd103

"Although cobalt - 60 and cesium - 137 have been used in the past, iridium - 192 is the most commonly used radioisotope in HDR brachytherapy".                                                                       — The physics of radiation therapy Note - Cs-137 is used in HDR brachytherapy, while option c i.e. Cs - 133 (not Cs - 137).