Balanced steady-state free precession imaging and its applications: From “steady state” to “transient state”

• Main Authors: Teng-Yi Huang, 黃騰毅
• Other Authors: Hsiao-wen Chung
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/86661050386567138921

博士 === 國立臺灣大學 === 電機工程學研究所 === 92 === Rapid gradient-echo imaging (bSSFP) with balanced gradient waveforms in all three gradient channels has recently raised significant attention in clinical practice. The aim in this work is to develop the new bSSFP techniques and applications. In the thesis, the bSSFP techniques are separated into two different categories, steady-state and transient-sate. First, the classic theory of steady-state bSSFP is shortly discussed. And a newly invented fat-water separation method using the phase property of bSSFP is demonstrated. We demonstrate the feasibility of fat/water separation in bSSFP imaging using the Dixon method in vivo at high magnetic field (3.0 Tesla), with cautions in its usage and optimal off-resonance ranges described using both theories and experimental results. Second, the concept of “transient-state” is introduced and demonstrated by simulations and volunteer brain images. We show that the usual appearance of bSSFP images should be more appropriately regarded as a transient-state combination of proton-density and T2/T1 contrast. The actual image appearance depends on the number of RF pulses experienced by the magnetization prior to data acquisition near the center portion of the k-space. Finally, the transient-state effect combined with T2 magnetization preparation and prospective motion-navigation is applied on the application of myocardial BOLD imaging. Combining T2 magnetization preparation, the transient-state bSSFP, which acquires signal before entering into steady-state, was shown practical to obtain T2-weighted images without segmented acquisition. In the present study, ECG-triggered bSSFP with T2 preparation was proposed to accomplish myocardial T2 mapping on human subjects, with special care taken on the phase-encoding order and motion control.