en Medical Physics and Radiation Therapy Medical Physics and Radiation Therapy Original Research Original Research <strong>Background: </strong>Measuring background radiation (BR) is highly important from different perspectives, especially from that of human health. This study was conducted to measure BR in the southeast of Iran.<br> &nbsp;&nbsp; <strong>Methods:</strong> BR was measured in Hormozgan and Sistan-Bluchestan provinces using portable Environmental Radiation Meter Type 6-80 detector. The average value was used to calculate the absorbed dose rate and indoor annual effective dose (AED) from BR. In addition, excess lifetime cancer risk (ELCR) was evaluated.<br> &nbsp;&nbsp; <strong>Results: </strong>The results showed that the maximum and minimum absorbed dose rates were 71.9 and 34.2 nGy.h-1 in Abomoosa and Minab in Hormozgan province and 90.0 and 47.8 nGy.h-1 in Zahedan and Chabahar in Sistan-Bluchestan province, respectively. Data indicated that these areas had a lower BR level compared with the worldwide level.&nbsp; The ELCR from indoor AED was larger compared with the worldwide average of 0.29 &times; 10-3.<br> &nbsp;&nbsp; <strong>Conclusion:</strong> This study provided a reference for designing and developing specific regional surveys associated with the measurement of natural BR in the southeast of Iran.<br> &nbsp; Background radiation, Environmental radiation, Absorbed dose rate, Annual effective dose 404 407 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-4479-4&slc_lang=en&sid=1 Mohammad Haghparast moh.haghparast@gmail.com 200319475328460064013 200319475328460064013 No Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, & Department of Radiology, Faculty of Paramedicine, Hormozgan University of Medical Sciences, Bandar-Abbas, Iran Mahdieh Afkhami Ardekani m.afkhami87@gmail.com 200319475328460064014 200319475328460064014 Yes Department of Radiology, Faculty of Paramedicine, Hormozgan University of Medical Sciences, Bandar-Abbas, Iran Mahmoud Navaser mahmoudrt1992@gmail.com 200319475328460064015 200319475328460064015 No Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Soheila Refahi s.refahi@arums.ac.ir 200319475328460064016 200319475328460064016 No Department of Medical Physics, Faculty of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran Milad Najafzadeh Miladnajafzadeh1370@gmail.com 200319475328460064017 200319475328460064017 No Department of Radiology, Faculty of Paramedicine, Hormozgan University of Medical Sciences, Bandar-Abbas, Iran Hamed Ghaffari hamedghaffari@yahoo.com 200319475328460064018 200319475328460064018 No Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Mahboubeh Masoumbeigi m.masoumbeigi@gmail.com 200319475328460064019 200319475328460064019 No Department of Medical Physics & Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran