Avaliação da exposição médica e ocupacional em procedimento cardíaco de radiologia intervencionista pediátrica utilizando modelagem computacional

Abstract

In this work, we modeled some pediatric interventional cardiology exposure scenarios using 10-year-old virtual anthropomorphic phantoms to represent a female and a male pediatric patient with cardiac anomaly. The cardiologists were positioned at 20 cm on the right side of the patient, and were represented by a male (MASH3) and a female (FASH3) adult anthropomorphic phantom. A total of 198 exposure scenarios were simulated, comprising an adult standing phantom and a pediatric phantom lying on a bed, both coupled with the MCNPX2.7.0 radiation transport code. The evaluation of occupational and medical exposures was performed using six beam projections, commonly employed in angiographic procedures, with X-ray equipment operating with tube voltages of 60, 70 and 80 kVp, and using a total filtration of 3.0mm Al + 0.1mmCu. We also evaluated the protective personal equipment (PPE) and suspended protective equipment used by professionals, and for this purpose nine types of exposure scenarios were considered. A general behavior of conversion coefficients for equivalent (CC[HT]) and effective (CC[E]) doses for occupational and medical exposure is that they increase with increasing in the tube voltage. The patient's organs with the largest contributions to the effective dose were the colon, lung, esophagus, stomach, and liver. The maximum average CC[E] value for the patient was 2.3E-01 mSv/Gy.cm² (80 kVp), which is higher than the literature results for pediatric patients, which were obtained using mathematical anthropomorphic phantoms. Results for the medical staff depend if the protective equipment are used. When professionals use PPE and suspended lead glass shield, the maximum average CC[E] value is 4.6E-02 µSv/Gy.cm². On the other hand, if the lead apron, the suspended lateral protector and the lead curtain, attached to the operating table, are not used, the average increase in CC[E] is 1925%, 383%, 168%, respectively. Another important fact is that 35% of occupational exposure may be attributed to radiation that reaches the organs and tissues of professionals through the lateral cavities of the lead apron and, therefore, this study recommends that professionals use more adjusted aprons. In addition to these results, two models of face protectors (F1 and F2) and one lead eyewear (M1) were evaluated. The results showed that the use of face protectors may reduce the CC[HT] values by up to 89%. However, using the M1 lead eyewear model, compared to the reference model, on average was not effective in reducing the exposure of physician’s eye lens. In addition to the conversion coefficients, a 3D distribution of the scattered radiation inside the room was obtained and, thus, it is possible to provide to the professionals a visual resource that enables the adoption of a safer position during interventional cardiology procedures.