Avaliação computacional das doses de radiação em radiografias de tórax de neonatos em UTI

Abstract

Chest radiographs in neonatal patients are an essential diagnostic resource in neonatal intensive care units (NICUs), widely used for clinical monitoring and the assessment of respiratory and cardiovascular conditions. Although these procedures are fast, efficient, and relatively accessible, they involve radiation doses that, despite being low, may present an increased risk due to the high radiosensitivity of neonates and the frequency of repeated examinations during hospitalization. In this context, the present study aims to investigate the absorbed doses in different organs during neonatal chest X-ray examinations through Monte Carlo simulations. The MCNP6.3 radiation transport code was employed, using neonatal anthropomorphic phantoms provided by ICRP Publication 143, inserted into a virtual environment representing a NICU, including an incubator and a mobile X-ray unit. Simulations considered different tube voltages (45 to 65 kV) and field sizes (10×10 cm², 15×15 cm², and 20×20 cm²), quantifying entrance skin dose and doses to radiosensitive organs such as the eye lenses and thyroid. The validation of the simulated results was performed through experimental measurements with the Black Piranha with accessories (RTI Group AB). The results indicated that increasing tube voltage was the main factor leading to higher absorbed doses, while enlarging the irradiated field had a smaller impact but resulted in the inclusion of non-essential organs, such as the eye lenses and brain, in the primary beam. Conversely, smaller fields proved effective in reducing dose without compromising image quality. It is concluded that the application of optimized protocols, with emphasis on strict collimation and appropriate tube voltage, can significantly reduce radiation doses received by neonatal patients in radiology, reinforcing the importance of the ALARA principle in clinical practice.