Dissertação de Mestrado
Validação e aplicação da metodologia computacional PCXMC para medida de dose em pacientes submetidos a exames de raios-X médico convencional
Vania Lucia Soares de Oliveira
The use of x-rays to produce images for diagnostic radiology has increased year by year and it is expected to increase further due to the benefits for better diagnosis of many pathologies. In spite of the benefits, inherent radiation risks have brought many concerns of the related radiation detriment. In diagnostic radiology with x-rays, risks are considered to be very low, but it is recommended that patient exposures should be controlled aiming the minimization of biological effects. Radiation risks can be reduced without any prejudice to the image quality by optimizing and assuring the quality of the radiographic procedures. Experimental and computational methodologies have been used to issue dose levels of patients submitted to exams in diagnostic radiology. In-vivo measurements during radiographic exams are difficult to be adopted; organ absorbed doses based on indirect measurements in the radiation beam or in human body phantoms can be carried out but they are hard and very time consuming. Computational systems are easily and largely used to estimate patient doses without interferences on the exams in compliance with legal requirements. In Brazil, the law Basic radiation protection guidelines for medical and dental diagnostic radiology did not required the evaluation of patient doses but internationally accepted diagnostic reference levels were issued. Very few hospitals have adopted any patient dose measurement and there is a lack of information on the dose values provided to patients undergoing different diagnostic exams. The aim of this work was to apply the PCXMC® computational software to evaluate the contribution given by each relevant organ to the effective dose, which is represented by the weighted equivalent dose, for patients submitted to chest, skull and pelvis x-ray examinations in a hospital unit of Belo Horizonte city, Brazil. The PCXMC® was validated by comparing the calculated absorbed dose values against experimental measurements done with thermoluminescent dosimeters in a Alderson Rando antrophomorphic phantom. X-ray phantom exposures were done in standard laboratoty conditions in the Development Center for Nuclear Technology. Examinations of sixty patients were followed and their data and radiographic parameters were classified in three biotypes for simulation purpose with the PCXMC®. Results showed that there were large patient dose variations due to their biotype and the adopted radiographic techniques. The PCXMC® proved to be an adequate tool that can be used with no difficulty by hospitals to evaluate and record patient doses.