Monte Carlo simulation of digestive and bladder positive contrast in pelvic CT scan examination: radiation dose and cancer risk assessment.

Abstract

This study aimed to evaluate the impact of digestive and bladder positive contrast agents (CA) on radiation dose and cancer risk during pelvic computed tomography (CT) scans using Monte Carlo simulation with the GATE platform and computational phantoms. The Siemens Emotion 16-slice CT scanner model was validated by comparing measured and simulated CTDIvol values using pelvic CT parameters. The densities and chemical compositions of CAs (Gastrografin® 30% and Utravist® 30%) were incorporated into the bladder and rectal cavities of Female Adult mesh (FASH) and Male Adult mesh (MASH) phantoms. Organ doses were simulated for scenarios using bladder CA (DU), digestive CA (DD), and both CAs (DDU). The dose enhancement factor (DEF) and lifetime attributable risk (LAR) were calculated using the Biological Effects of Ionizing Radiation (BEIR) VII model, considering a reference age of 30 years.The highest effective dose was observed in females (4.83 mSv) compared to males (2.61 mSv). The small intestine (22.35 mGy) and uterus (27.64 mGy) recorded the highest absorbed doses. Positive CAs significantly reduced radiation dose and cancer risk, with the greatest reductions achieved when both CAs were applied (mean DEFDU,male = 0.68, mean DEFD,male = 0.75, DEFU,male = 0.90). Specific reductions were noted for Organs containing CA, including the bladder (DEFDU,male = 0.41, DEFDU,female = 0.55) and small intestine (DEFDU,male = 0.52, DEFDU,female = 0.53). Cancer risk reductions ranged from 8.84% to 38.86% in females and 5.24% to 33.65% in males, with reductions of 19.59% for the uterus, 29.20% for the ovaries, and 40.84% for the prostate.The shadowing effect of enhanced cavities demonstrated a significant reduction in radiation dose and cancer risk, highlighting potential applications of CAs in clinical practice to improve safety.