en Other Other Original Article Original Article <div style="text-align: justify;">Computed tomography (CT) is one of the most important diagnostic X-ray procedures which plays an important role in increasing the patient dose values. The purpose of this clinical study was to evaluate the efficacy of vitamins E and C in lowering down the level of DNA double strand break (DSB) caused by CT scan. Sixty patients for abdomen/pelvic enhanced CT scan were randomly assigned to placebo (control), vitamin C, and vitamin E groups. The patient blood samples were taken before and immediately after the CT scan. Counting the number of DSB was performed using &gamma;-H2AX method as a sensitive biomarker. Immediately after the CT scan, the mean number of DSBs/cell increased in all three groups of control (131%, P < 0.001), vitamin C (103%, P < 0.001), and vitamin E (66%, P < 0.001) compared to their mean before the CT scan. Furthermore, the results showed that vitamin E decreased the mean number of DSBs/cell by 22% in comparison with the control group (P = 0.023), whereas vitamin C had no significant effect on reducing the DSB (<3%, P = 0.741). It is concluded that the administration of vitamin E one hour before the CT scan, significantly decreases DSB levels.</div> Computed tomography (CT), DNA double strand break (DSB), vitamin C, vitamin E 226 233 http://ijmcmed.org/browse.php?a_code=A-10-1606-1&slc_lang=en&sid=1 Seyed Masoud Jafarpour mjradiology@yahoo.com 100319475328460014140 100319475328460014140 No Department of Radiology and Medical Physics, Faculty of Paramedicine, Kashan University of Medical Sciences, Kashan, Iran. Morteza Salimian Salimiam@yahoo.com 100319475328460014141 100319475328460014141 No Department of Medical laboratory, Faculty of Paramedicine, Kashan University of Medical Sciences, Kashan, Iran. Mehran Mohseni mehran.m1352@yahoo.com 100319475328460014142 100319475328460014142 Yes Department of Radiology and Medical Physics, Faculty of Paramedicine, Kashan University of Medical Sciences, Kashan, Iran. Hamid Reza Talari hrtalari@gmail.com 100319475328460014143 100319475328460014143 No Department of Radiology, Kashan University of Medical Sciences, Kashan, Iran. Akbar Aliasgharzadeh aliasgharzadeh@yahoo.com 100319475328460014144 100319475328460014144 No Department of Radiology and Medical Physics, Faculty of Paramedicine, Kashan University of Medical Sciences, Kashan, Iran. Bagher Farhood bffarhood@gmail.com 100319475328460014145 100319475328460014145 No Department of Radiology and Medical Physics, Faculty of Paramedicine, Kashan University of Medical Sciences, Kashan, Iran. Habiballah Moradi Moradih1348@gmail.com 100319475328460014146 100319475328460014146 No Department of Radiology and Medical Physics, Faculty of Paramedicine, Kashan University of Medical Sciences, Kashan, Iran. Hossein Safari hossein.comely@gmail.com 100319475328460014147 100319475328460014147 No Health promotion research center, Iran University of Medical Sciences, Tehran, Iran.