Computational retrospective dosimetry with fortuitous dosimeters: An inter-laboratory comparison and evaluation of dose conversion coefficients

In large-scale radiological accidents, retrospective dose assessment is crucial for individuals without personal dosimeters. This study investigates the applicability of computational dosimetry and dose conversion coefficients (DCCs) using mobile phones as fortuitous dosimeters. A realistic exposure scenario was created using anthropomorphic phantoms and an Ir-192 source. Monte Carlo simulations were performed by three institutions in the Korea Retrospective Dosimetry network (KREDOS), applying ICRP mesh-type reference computational phantoms to estimate whole body dose (WBD) and effective dose (ED). Inter-laboratory comparisons showed z-scores less than 2 for all participants, confirming consistency in computational methods. To validate DCCs, WBDs were reconstructed from mobile phone measurements using both generalized (DCC ge ) and individual (DCC in ) coefficients, and compared with simulated reference doses (WBD sim ). DCC-derived WBDs showed overall improved agreement with WBD sim at the chest and hip attachment positions compared to direct mobile phone dose measurements. For instance, at the chest position, mobile phone doses overestimated WBD sim by up to a factor of 2.46, whereas WBD in (DCC in -derived WBD) and WBD ge (DCC ge -derived WBD) were improved to ranges of 0.75–1.36 and 1.57–2.17 times WBD sim , respectively. At the hip position under AP irradiation, mobile phone doses corresponded to only 25–36% of WBD sim , while WBD in and WBD ge approached the reference values at 94–109% and 71–102%, respectively.