鍾孝文臺灣大學：電機工程學研究所王福年Wang, Fu-NienFu-NienWang2007-11-262018-07-062007-11-262018-07-062005http://ntur.lib.ntu.edu.tw//handle/246246/53015我們提出一種適合在高磁場下使用的擴散張量影像技術。運用平面回訊影像(EPI)做為螺旋槳式(PROPELLER) k空間軌跡的讀取模組，因此稱為螺旋槳式平面回訊影像。因為平面回訊影像對於磁場不均造成的的偏振現象非常敏感，我們提出的螺旋槳式平面回訊影像技術包含了一系列的修正方法。在3T高磁場下的實驗結果顯示，與單次激發的平面回訊影像相較，螺旋槳式平面回訊影像有效減低了影像幾何失真的問題；螺旋槳式快速自旋回訊影像(FSE)造成的高特定射頻吸收率(SAR)的問題也得到改善。螺旋槳式平面回訊影像的自我導航相位修正能力對於擴散張量影像也非常的有效。平面回訊影像減少了資料擷取時間，所以可以在較短時間內得到較多資料而提高訊雜比。因此與常用的單次激發平面回訊影像比較，在同樣的掃描時間下，螺旋槳式平面回訊影像的高訊雜比在擴散張量影像的臨床應用上有較大的優勢。A technique suitable for diffusion tensor imaging at high field strengths is presented in this thesis. The method is based on PROPELLER k-space trajectory using EPI as the signal readout module, hence dubbed PROPELLER EPI. The implementation of PROPELLER EPI included a series of correction schemes to reduce possible errors associated with the intrinsically higher sensitivity of EPI to off-resonance effects. Experimental results on a 3.0 Tesla MR system showed that the PROPELLER EPI images exhibit substantially reduced geometric distortions compared with single-shot EPI, at a much lower RF specific absorption rate than the original version of PROPELLER fast spin-echo technique. For diffusion tensor imaging, the self-navigated phase correction capability of the PROPELLER EPI sequence was shown to be effective for in vivo imaging. The reduced data acquisition window also allows more signal averages to be performed to achieve higher signal-to-noise ratio when compared with single-shot EPI at identical total scan time, an advantage beneficial for routine diffusion tensor imaging applications in clinical practice.Abstract 中文摘要 Chapter 1 Introduction Reference 1-5 Chapter 2 Principles of EPI 2.1 EPI sequence 2-3 2.2 EPI Artifacts 2-7 2.2.1 N/2 ghost 2-8 2.2.2 Chemical shift 2-10 2.2.3 Field inhomogeneity 2-11 2.2.4 T2* blurring 2-14 2.3 Other EPI techniques 2-15 2.3.1 Segmented EPI 2-15 2.3.2 EPI with parallel imaging 2-16 2.3.3 Field map correction 2-18 References 2-22 Chapter 3 PROPELLER with EPI read out 3.1 PROPELLER principles 3-2 3.2 PROPELLER with EPI read out 3-5 3.2.1 Spatial registration 3-8 3.2.2 Phase correction 3-9 3.2.3 Further reduction of off-resonance effects via triangular windowing 3-9 3.2.4 Density compensation and data combination 3-12 3.2.5 Off-resonance correction with field map 3-12 3.2.6 Parallel imaging 3-14 3.3 Imaging experiments 3-16 3.4 Discussions 3-27 References 3-31 Chapter 4 Application: Diffusion Tensor Images 4.1 Diffusion weighted imaging 4-4 4.2 Diffusion Tensor imaging 4-8 4.3 Experiments: PROPELLER DTI v.s. conventional DTI 4-11 4.4 Discussions 4-22 References 4-25 Chapter 5 Conclusion References 5-72538575 bytesapplication/pdfen-US螺旋槳式影像平面回訊影像幾何失真特定射頻吸收率擴散張量影像Propeller imagingEPIgeometric distortionsspecific absorption ratediffusion tensor imagingthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/53015/1/ntu-94-D89921035-1.pdf