Effects of lens shielding on computed tomography using MCNP

Dosimetry in computed tomography (CT) has become increasingly important due to the increasing use of this diagnostic technique. To understand and quantify the risk associated with CT examinations, an effort has been made to more precisely determine the radiation dose to radiosensitive organs such as the lens. Although the target organ of interest is far from the eyes, in many radio-diagnostic studies the lens is exposed to unnecessary radiation due to its dispersion, which is why dose reduction techniques have become a topic of interest such as the use of shielding. In this work, a tomographic study was simulated to calculate the dose in the lens with and without shielding in different configurations, by constructing an X-ray tube using the MCNP code. Our main results show the validation of the X-ray spectrum obtained by the simulation, the characteristic X-rays correspond to the energy transitions identified and reported by Nist. The absorbed dose in the lens due to radiation from both the direct beam and scattered radiation estimated in this work was 42.8 ± 0.49 mGy and an effective dose of 5.14 ± 0.06 mSv. The presence of a shielding system leads to a reduction in the dose to the lens from 21.0 % to 74.0 %. The shields whose results compare best with those obtained by using a commercial shield were the ^Bi Individual and ^Pb Individual shields with a relative dose attenuation of 23.6 % and 27.3 %, respectively. (author)