Avaliação da dose em exames de tomografia computadorizada pediátrica por tamanho específico do paciente

Abstract

Computed Tomography (CT) is considered one of the most important diagnostic imaging methods. However, despite several advances, CT exams are responsible for more than half of the dosage of ionizing radiation to which patients are submitted if compared to other modalities in radiodiagnostics. The purpose of this study was to evaluate the dose of ionizing radiation used in CT scans of the Head, Chest, and Abdomen in children aged 0 to 10 years old, according to its physical characteristics, correlating the data collected from the calculated dose with the reference values of international recommendations and recent regulations published by the national regulatory agency (ANVISA) for CT exams. In this study, 201 results, performed using the helical acquisition method were analyzed and grouped according to their inherent characteristics and the body region exposed during the CT exam. The radiation dose was estimated considering the specific dimensions of each patient using the values of Computed Tomography Dose Index Volumetric (CTDIvol) recorded by the scan and the values obtained from dosimetry. The dose of ionizing radiation absorbed by the organs and the effective dose was estimated through the CTDIvol referring to dosimetry, using the CALDose_XCT software. Furthermore, the effective dose was also estimated using a simplified method proposed by the European Working Group on Guidelines on Quality Criteria in CT. The values corresponding to the dose index estimate, CTDIvol and Size Specific Dose Estimates (SSDE), concerning the collected data and the data obtained through dosimetry with the phantom for all groups, according to the region of examination, are acceptable in relation to the reference values established by international recommendations and by ANVISA, even though the tube voltage values used in most exams do not correspond to the ideal values for pediatric exams, as indicated in the literature. The effective dose values are also lower than the typical values established by the American Association of Physicists in Medicine (AAPM), except for the group of patients ≥ 6 years for Head exams, with a variation greater than 17% of the maximum typical value of 2 mSv. Nevertheless, a continuous verification and optimization of the technical parameters are recommended, in order to enable the constant updating of the typical acceptable dose values, thus preventing the values exceed the reference values.