Dose estimation in reference and non-reference pediatric patients undergoing computed tomography examinations: a Monte Carlo study

Abstract

-The global increase in the number of computed tomography (CT) examinations have enhanced concerns regarding stochastic radiation risks to patients, especially for children. Considering that cancer risk is cumulative over a lifetime and each CT examination contributes to the lifetime exposure, there is a need for a better understanding of radiation-induced cancer incidence and mortality, and better dose estimates. Accordingly, some authors estimated organ and effective dose in reference phantoms, but still there is a critical need to expand these data to larger groups of non-reference children. As an initial step to address this issue, in this study organ and effective doses were calculated in common CT procedures in non-reference pediatric phantoms and were compared with those of reference phantoms with the similar ages. Thirteen pediatric phantoms, BABY CHILD, five voxel-based UF pediatric phantoms (B-series) and six phantoms developed at The Foundation for Research on Information Technologies in Society (IT'IS) were implemented into MCNP. According to the results, there were no consistent differences between the doses of organs exposed indirectly and effective doses of these three phantom types, but it was observed that for organs located in the scan region, there was a relation between absorbed doses and pediatric age group, as expected. Generally, using the results of this study one can estimate the absorbed doses more accurately. But it should be noted that these low expansion data are not comprehensive enough for finding a reasonable relationship between phantom size and effective dose except in chest-abdomen-pelvis (CAP) imaging.Keywords: Pediatric computed tomography / reference and non-reference phantoms / age and size dependent absorbed dose / effective dose estimation

Dose estimations for Iranian 11-year-old pediatric phantoms undergoing computed tomography examinations

“…In addition, it was observed that there is a good agreement between the results of peripheral CTDI values obtained by simulation and measurement (<5% difference). For instance, the measured and simulated values of peripheral CTDI at 12:00 at a tube voltage of 80 kVp were 6.83 and 6.53 mGy, respectively [ 15 , 16 ].…”

“…Moreover, the peripheral CTDI value at 12 o'clock was measured, and it was then compared with the result of the simulation. A 10-cm pencil-shaped Radcal® ion chamber model 10×5-3CT (Radcal Corporation, Monrovia, CA) and a Radcal 9015 dosimeter (Radcal Corporation, Monrovia, CA) were used to determine the CTDI values [ 15 , 16 ]. To perform the comparison, the CTDI head and body phantoms were modeled as cylinders having a diameter of 16 cm and 32 cm, respectively, with a length of 15 cm each.…”

A Monte Carlo study on quantifying the amount of dose reduction by shielding the superficial organs of an Iranian 11-year-old boy

“…Given the outcomes, the importance of modeling true location of all organs in human anatomy is explicit. [38] In the study based on stylized phantom, the testes dose reduction was 9%, whereas in this study, this value rises up to 58%. Because of these more accurate results, no one should ignore placing lead shield on testes in abdomen-pelvis scan.…”

The effects of simulating a realistic eye model on the eye dose of an adult male undergoing head computed tomography

“…Several scientific groups investigated the dose values for the lens for electrons (Behrens et al 2009;Behrens 2013;Nogueira et al 2011), photons (Behrens and Dietze 2010), and neutrons (Manger et al 2012) in different irradiation scenarios. In CT examinations, the absorbed dose was calculated for a simple eyeball modeled in a stylized phantom (Akhlaghi et al 2015c), for eye, cornea, and lenses in a stylized head phantom , and also for eye bulb and lens using voxel phantoms (Akhlaghi et al 2015b;Lee et al 2011). In contrast, in this study, for the first time one of the most detailed eye models including almost all the relevant parts was used, to provide more accurate results for the dose and consequently the risk assessments after head CT scans.…”