en Radiation Biology Radiation Biology تحقيق بديع Original Research <p><strong>Background:</strong> Technetium-99m radioisotope is the backbone of any nuclear medicine institute. This radioisotope is acquired by the elution of Molybdenum-99/Technetium-99m generator which emits 141 keV gamma ray and having 6.04 hour half-life. Occasionally the contents of Molybdenum-99 may mix up with elute, which may affect image quality and patients may receive higher doses than recommended. This study was initiated to check and evaluate the contamination of Molybdenum-99 in Molybdenum-99/Technetium-99m generators used at Nuclear Institute of Medicine and Radiotherapy (NIMRA) Jamshoro Pakistan before its administration to patients for diagnostic procedures. <strong>Materials and Methods:</strong> The Molybdenum-99 impurity in Technetium-99m elute for 50 generators was studied during the year 2012. The measurements were made using dose calibrator and a standard canister at the time of first elution of the generators. The dose calibrator displays result after executing various steps in a sequence. Due to some production process error or any mechanical fault high activity of Molybdenum-99 was recorded and removed with decrease in Technetium-99m yield. <strong>Results:</strong> The most of eluted generators (90%) contained 10% of molybdenum breakthrough of the permissible limit (P < 0.05). The high activity of Molybdenum-99 was recorded in only 6% of the generator and removed by using standard methods with some reduced Technetium-99m activity. <strong>Conclusion:</strong> The molybdenum breakthrough was according to recommended standards in most of the generators. The removal of high contents of Molybdenum-99 enabled the institute to continue routine imaging services by improved image quality and reduction in radiation dose to the patients.</p> Dose calibrator, 99Mo-99mTc generator, 99Mo, molybdenum breakthrough, 99mTc 343 346 http://ijrr.com/browse.php?a_code=A-10-1-526&slc_lang=en&sid=1 S.A. Memon physicistsajjad@hotmail.com 790031947532846009435 790031947532846009435 Yes Nuclear Institute of Medicine and Radiotherapy (NIMRA) Jamshoro, Pakistan N.A. Laghari 790031947532846009436 790031947532846009436 No Nuclear Institute of Medicine and Radiotherapy (NIMRA) Jamshoro, Pakistan S.T. Qureshi 790031947532846009437 790031947532846009437 No University of Sindh, Jamshoro, Pakistan F. Mehdi 790031947532846009438 790031947532846009438 No Nuclear Institute of Medicine and Radiotherapy (NIMRA) Jamshoro, Pakistan