| Summary: | 碩士 === 義守大學 === 資訊工程學系碩士班 === 98 === Magnetic Resonance Imaging (MRI) techniques have been extensively improved in the past 20 years and have been recognized as a potential technique in the clinical diagnosis of diseases as well as tumor localization. MRI has the advantages of three-dimensional imaging capability, no radiation and non-invasive examination. One of the crucial issues of MRI is the geometric distortion caused by magnetic field inhomogeneity, especially in low-field strength ≦0.5T MRI. The farther the lesion away from the center (off-center field) is, the more distortion it creates. It might cause difficulty in evaluating the lesion.
The purpose of this study was to use a home-made water-phantom to evaluate the geometric distortion of MR image. The results can be provided to clinical doctors as a reference to improve the diagnostic accuracy of the MR image. Based on the findings of our study, we have demonstrated that the geometric distortion of an MR image begins initially from the center of the magnetic field, then gradually spread outwards as the image distortion become worsen. The image distortion is more serious outside the area of the 24cm × 24cm field of view (FOV). Therefore, in performing specific MR images of the thorax, abdomen, pelvis as well as the extremity, it is suggested that lesion be placed at the center of the magnetic field in order to avoid further distortion of the MR image.
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