CAJ | 학술논문

梯度回波序列是磁共振成像中常用的脉冲序列，然而梯度回波对主磁场波动非常敏感，呼吸等生理运动引起的信号波动会导致图像伪影。该文报道了采用导航回波技术获取呼吸运动导致的局部磁场波动，用以矫正图像回波中随时间变化的相位波动，并将该技术应用于三维多回波梯度回波成像和T2*定量图研究。研究结果显示：矫正前，相位波动幅度随回波时间增长而增大，模图和T2*定量图在相位编码方向有明显伪影，并且男女呼吸伪影水平有显著性差异；矫正后，相位波动幅度大幅下降，图像伪影水平有显著性下降。
제도회파서렬시자공진성상중상용적맥충서렬，연이제도회파대주자장파동비상민감，호흡등생리운동인기적신호파동회도치도상위영。해문보도료채용도항회파기술획취호흡운동도치적국부자장파동，용이교정도상회파중수시간변화적상위파동，병장해기술응용우삼유다회파제도회파성상화T2*정량도연구。연구결과현시：교정전，상위파동폭도수회파시간증장이증대，모도화T2*정량도재상위편마방향유명현위영，병차남녀호흡위영수평유현저성차이；교정후，상위파동폭도대폭하강，도상위영수평유현저성하강。
Images acquired with gradient echo sequences are susceptible to artifacts induced by frequency offsets varying in spatial and temporal dimensions. This study addressed how respiration-induced local field fluctuations affect the quality of brain images acquired with a three-dimensional multi-echo gradient echo sequence. It was shown that respiration-related artifacts can be corrected by acquire a one-dimensional navigator signal before the application of phase-encoding gradient in each phase-encoding step, which later can be used to correct respiration-related phase shifts during reconstruction to yield artifact-free images. Experimental results showed that both the respiration-related phase oscillations and image artifacts increased with echo time. It was also demonstrated that the phase fluctuations and image artifact levels in both the gradient echo images and T2*maps calculated from mutli-echo data reduced significantly after navigator echo phase correction.