| Summary: | 博士 === 國立臺灣大學 === 生醫電子與資訊學研究所 === 100 === Two improved 2D phase correction methods were proposed in this thesis to increase the effectiveness of ghost reductions of low-resolution blade images, and to solve the issue of ghost reduction within large signal-free regions. N/2 ghost artifact is a significant issue of EPI readout techniques. Thus, ghost reduction of each blade data is an essential processing step prior to PROPELLER-EPI reconstruction. PROPELLER-EPI acquires a set of rotating blades with different rotating angles to fill out the entire k-space. Most of rotating blades are oblique acquisition with EPI readout, which result in oblique ghost with echo shift and interlaced sampling. Either the improved reference-based 2D phase correction or the improved reference-free 2D phase correction can help to reduce the residual oblique ghost when using 1D phase correction, thus increase the image quality of each blade data before applying PROPELLER-EPI reconstruction. The proposed improved 2D phase correction methods were demonstrated, both of which exhibit good immunity to motion. Three preliminary clinical results, ADC measurement in parotid glands, brain DWI with motion correction, and free-breathing liver DWI, showed the possible application of PROPELLER-DW-EPI with the two improved 2D phase correction methods. In addition, the reference-free 2D phase correction method can eliminate the need of reference scan time of each blade, and thus may broaden the clinical use of PROPELLER-DW-EPI.
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