Doses e risco da radiação em pacientes submetidos a exames de corpo inteiro de 18F-FDG PET-CT para diagnóstico oncológico

Abstract

Patients submitted to PET-CT examinations might be exposed to radiation levels, higher than those from other diagnostic techniques. The reason is that PET-CT complies two radiation exposures: one from the intravenous injection of the radiopharmaceutical and the other from the computerized tomography. The study of the mean absorbed dose in an organ and the effective dose in patients undergoing PET-CT examination is relevant to allow the optimization of diagnostic radiology procedures in order to follow the principles of radiation protection. In this work, the absorbed dose in several organs and the effective dose in patients submitted to PET-CT exams with the radiopharmaceutical 18F-FDG were assessed. The ICRP-106 biokinetic model and thermoluminescent detectors in a anthropomorphic phantom were used. In order to reduce the patient dose, new protocols for image acquisition were also evaluated. In addition, the risk of cancer induction for the patients was estimated. The use of the PET-CT image acquisition protocol, with the CT protocol for anatomical mapping, showed that 60% of effective dose was from the radiotracer administration, being the effective dose values for a typical male patient of (8.51 ± 2.21) mSv and female (5.80 ± 1.57) mSv. It was also noticed that the optimized protocol for PET-CT image acquisition reduced the risk of inducing fatal cancer in approximately 23 % for both male and female patients. In conclusion, patient doses can be reduced by using appropriate imaging acquisition in 18F-FDG PET-CT examinations and promoting the compliance with the radiation protection principles.