en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;">Background: In Southeast Europe medical accelerators are sometimes placed in small vaults originally built for ⁶⁰Co treatment unit. In order to meet shielding requirements for high energy photon beams, the wall thickness had to be increased. Since the vaults are already limited in size, instead of adding more concrete, materials with high-Z elements were used. Limited vault size and addition of high-Z elements can contribute to the neutron dose equivalent for both medical personnel and patients. Materials and Methods: The most commonly used empirical equations for estimation of neutron dose equivalent at the maze door in the vault are by Kersey and Wu-McGinley. In order to assess accuracy of these equations, Monte Carlo (MC) simulations of various geometrical and compositional changes of vault were conducted. Neutron ambient dose equivalent (H^*_n(10)) was observed when dimensions of the vault walls were reduced gradually. Results: The empirical equations gave results with reasonable accuracy when vaults were of standard size. When the vault was decreased to the size of the usual ⁶⁰Co unit vault, the most commonly used equations showed significant difference in results (up to 90%) in comparison to MC simulations. MC simulations showed that introducing different materials in shielding can change the neutron dose equivalent in vicinity of accelerators. Conclusion: For vaults limited in size, new simplified equation for neutron dose equivalent at the maze doors is presented, although performing a MC simulation of the specific vault is suggested.</div> LINAC, vault, Monte Carlo simulations, radiotherapy, neutron ambient dose equivalent. 99 107 http://ijrr.com/browse.php?a_code=A-10-1-844&slc_lang=en&sid=1 A. Ivković 7900319475328460015409 7900319475328460015409 No Department of Biophysics and Radiology, Faculty of Medicine, J. J. Strossmayer University of Osijek, Croatia D. Faj 7900319475328460015410 7900319475328460015410 No Department of Biophysics and Radiology, Faculty of Medicine, J. J. Strossmayer University of Osijek, Croatia S. Galić 7900319475328460015411 7900319475328460015411 No Faculty of Medicine, University of Mostar, Bosnia and Herzegovina A.H. Karimi 7900319475328460015412 7900319475328460015412 No Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran M. Kasabašić 7900319475328460015413 7900319475328460015413 No Department of Biophysics and Radiology, Faculty of Medicine, J. J. Strossmayer University of Osijek, Croatia H. Brkić hbrkic@mefos.hr 7900319475328460015414 7900319475328460015414 Yes Department of Biophysics and Radiology, Faculty of Medicine, J. J. Strossmayer University of Osijek, Croatia