Geometrical Distortion Correction in Echo Planar Imaging using A Modify Reversed Gradient Method: Techniques & Applications
Date Issued
2006
Date
2006
Author(s)
Chang, Hing-Chiu
DOI
en-US
Abstract
A technique suitable for echo planar imaging (EPI) geometrical distortion correction is presented in this thesis. The method is based on reversed gradient method (RG) using phase-encoding gradient with reversed polarity that produces distortion in opposite direction, from which the information on the difference in spatial displacements is then used to correct for distortion. However, this method is problematic in regions with low signals because of a lack of information on distortions which leads an error correction in regions with low signals. The implementation of reversed gradient method induced a displacement map concept to reduce the error correction in regions with low signals. The displacement map concept consists of eliminating error displacement map, surface fitting and filtering. Experimental results on a 3.0 Tesla MR system showed that the modified reversed gradient method corrected images exhibit substantially reduced geometric distortions and correction error in regions with low signals compared with original reversed gradient method. Applied reversed gradient method in high-resolution DTI using PROPELLER EPI to extra correct each blade, shows benefits from the modified reversed gradient method. It can increase the image quality for routine diffusion tensor imaging applications in clinical practice.
Subjects
平面回訊影像
幾何扭曲
反向梯度磁場法
螺旋槳式磁振平面回訊影像
擴散張量影像
Echo Planar Imaging
EPI
geometric distortion
reversed gradient
PROPELLER EPI
diffusion tensor imaging
DTI
gradient revesal
Type
thesis
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