Evaluation of polyurethane composite shields effect on reducing the risk of cataract induction at head CT scan

Head computed tomography is a common diagnostic examination, which may cause lenticular opacity and cataracts. Cataract induction is one of the non-stochastic effects of radiation, that happens at threshold dose of 0.5 Gy. Recent studies illustrate that only irradiation to the sensitive (germinative) zone of the lens is a prerequisite to cataract development. Recently, the dose values absorbed in substructures of a detailed eye model at head CT scan has been evaluated. In the present work, the effect of shielding on flux reduction and dose to different eye substructures was investigated. For this purpose, after placing eye model in the head of ICRP adult male phantom, CT exposure was simulated at tube voltage of 80, 100 and 120 kVp by MCNPX Monte Carlo code. Dose values as well as photon flux were estimated without and with different bismuth-polyurethane composite shields. Given its advantages, polyurethane composite with bismuth concentration of 20% was selected as an appropriate protective shield. Results show that applying this composite shield reduces dose almost 70%, 65% and 60% at tube voltages of 80, 100 and 120 kVp, respectively.