Correção de aquisição e automatização da reconstrução GRASP de imagens de RM

• Ano de defesa: 2019
• Autor(a) principal: Rocha, Eduardo Baum
• Orientador(a): Azevedo, Dario Francisco Guimarães de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul
• Programa de Pós-Graduação: Programa de Pós-Graduação em Engenharia Elétrica
• Departamento: Escola Politécnica
• País: Brasil
• Palavras-chave em Português: Ressonância Magnética; Respiração Livre; GRASP; Compressed Sensing; Subamostragem Incoerente; Radial Golden Angle; Fibrose Cística
• Palavras-chave em Inglês: Magnetic Resonance; Free Breathing; GRASP; Compressed Sensing; Incoherent Subsampling; Radial Golden Angle; Cystic Fibrosis
• Área do conhecimento CNPq: ENGENHARIAS
• Link de acesso: http://tede2.pucrs.br/tede2/handle/tede/9998

The main objective of this work is to develop a system that allows the acquisition of magnetic resonance images of the thorax of patients with free breathing. Traditional techniques when used in patients who can not perform apnea result in high blurry images. Conventional MR imaging methods work by acquiring Cartesian- K space. In the proposed system we used the GRASP pulse sequence, Goldenangle RAdial Sparse Parallel, in conjunction with a reconstruction algorithm. The GRASP sequence acquires the images radially continuously, incremented by the radial golden angle constant. Subsequently, in the reconstruction process the respiratory movement is tracked, the separation of the spokes stars in respiratory stages and the reduction of subamplification artifacts using Compressed Senssing. After the acquisition of the RM data by the GRASP method, it is essential to optimize the acquired data to obtain adequate results. To perform this correction we reconstructed several exams of different patients, varying only this parameter in order to carry out more in depth analyzes of the attributes of these images. From these results, we developed a method that is based on the variance of the pixels of the images as a figure of merit in order to obtain the most reliable images, presenting totally satisfactory results. A total of 174 computerized tomography and magnetic resonance imaging examinations of 29 patients were performed. These examinations were evaluated clinically by two experienced radiologists. In the clinical evaluation, the GRASP method presented a high correlation with Computerized Tomography (reference) and quality equivalence with the conventional magnetic resonance imaging in apnea.