Organ and skin dose assessment in neonatal chest radiography using Monte Carlo simulation

Chest radiography is essential in neonatal intensive care units (NICUs), but repeated exposures raise concerns due to the high radiosensitivity of newborns. This study aimed to estimate entrance skin dose (ESD) and absorbed organ doses in neonates undergoing chest X-ray examinations, under varying exposure parameters, using Monte Carlo simulation. A realistic NICU scenario was modeled in MCNP6.3 Monte Carlo code, including a mobile X-ray unit, an incubator, and ICRP 143 neonatal reference phantoms. Simulations were performed for tube voltages ranging from 45 to 65 kV and radiation field sizes of 10 × 10 , 15 × 15, and 20 × 20 cm 2 . Experimental validation was carried out using a water phantom and a solid-state dosimeter. ESD ranged from 15.36 to 59.81 μ Gy, with a mean of 36.45 μ Gy. Absorbed organ doses varied widely: brain (0.14–1.31 μ Gy), lens (0.13–1.33 μ Gy), esophagus (6.46–52.51 μ Gy), stomach (25.50–118.40 μ Gy), liver (13.98–78.64 μ Gy), red bone marrow (0.71–10.50 μ Gy), kidneys (2.89–25.23 μ Gy), thyroid (1.82–29.59 μ Gy), and lungs (4.88–39.46 μ Gy). Dose increases were driven primarily by higher tube voltages and, most significantly, by the inclusion of the organ within the primary beam. These findings highlight the importance of strict collimation and optimized parameters in neonatal radiography, reinforcing the ALARA principle.