Avaliação da dose, qualidade da imagem e otimização de protocolos de crânio pediátrico em tomografia computadorizada

• Autor(a) principal: Rojas, Diego Jesús Rada
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/16314
• topic: CT Scanner; Dose; Quality Control; Pediatric; Cranial; Tomógrafo; Dose; Controle da Qualidade; Pediátrico; Cranial; Tomografia computadorizada; Diagnóstico por imagem; Diagnóstico por Imagem Normas; Dosagem de Radiação; Controle da Qualidade; Crânio Radiografia; Tomografia computadorizada; CNPQ::CIENCIAS BIOLOGICAS::BIOFISICA

Computed tomography is a powerful tool for diagnostic imaging of various diseases, but the exposure to ionizing radiation in pediatric patients in studies of cranial CT may develop complications in more radiosensitive tissues such as the eye lens and the inner ear, depending on the dose can appear quickly or with the passing of the years, so it is very important to have a balance between radiation dose and image quality. One important quality image parameter in Computerized Tomography is the Noise because it can significantly affect the visualization for the diagnostic and can be related with the dose on the patient by the x-ray tube voltage. In this work is tested the hypothesis that the quality parameter of image Noise and the radiation computed tomography dose indexes can vary as a function of the x-ray tube voltage in the different protocols for pediatric cranial and can get this done is a way to reduce the risks of exposure to ionizing radiation in pediatric cranial tomography practices, without altering the minimum quality required by health authorities. The gereral objective of this work is to generate indicators of image quality in cranial pediatric tomography correlated with radiation dosimetry, noise, low resolution and high contrast and accuracy in the axial plane. Using pediatric cranial CT protocols in patients aged 6 to 12 years, and using the phantom image quality MODEL ACCREDITATION PHANTOM 464 ACR CT, and the AAPM PHANTOM, was determined the high and low contrast, the accuracy of distance in the axial plane and the number of CT for different reference materials such as acrylic, polyethylene, water, bone and air and the computed tomography dose indexes. It was also determined the noise variation and the computed tomography dose indexes variation as a function of x-ray tube voltage. Was created a system of evaluation in pediatric cranial tomography, considering the Low and high Resolution, accuracy on the CT Number and accuracy of the Distance in the Axial Plane as basic parameters of quality image, determining accordance indexes with the minimal quality image in this parameters at eight CT Scanners of radiology services institutions that have significant magnitude in the state of Rio de Janeiro-Brazil. Was observed in these eight CT Scanners that the image noise in a reference material (water) and the computed tomography dose indexes for pediatric cranial protocols are a quadratic function of the of the x-ray tube voltage, leveraging these two properties was possible to find a value of the voltage at which the image noise and the computed tomography dose indexes are minimal, ensuring optimization of protocols reducing the dose up to 69% and respecting the Reference Dose levels set by the bodies under regulators. In turn, the evaluation system implemented in this work showed that five of the eight CT Scanners studied are at different quality levels of nonconformity for diagnostic use, urging the authorities to take corrective action. It was possible to reduce the computed tomography dose indexes of radiation and increase image quality in cranial pediatric protocols modulating x-ray tube voltage.