Taylor A M, Keegan J, Jhooti P, Firmin D N, Pennell D J
Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, Sydney Street, London, UK.
J Cardiovasc Magn Reson. 1999;1(2):131-8. doi: 10.3109/10976649909080841.
There has been conflicting data in the literature regarding the use of wide navigator echo (NE) acceptance windows in combination with adaptive motion correction for magnetic resonance coronary angiography (MRCA). This in part may be due to the use of a fixed correction factor when applying the adaptive motion-correction algorithm, which may potentially result in miscorrection of the imaging slice in subjects whose correction factor differs widely from the mean. We have addressed this issue by measuring the superior/inferior correction factor in 25 subjects and assessing the effect of using a subject-specific correction factor (CFss) for MRCA in comparison with no adaptive motion correction (CF0) and erroneous adaptive motion correction with a correction factor of 1.0 (CF1). There was a wide variation in the correction factor between subjects (proximal right coronary artery, 0.49 +/- 0.15, range 0.20-0.70; proximal left coronary artery, mean 0.59 +/- 0.15, range 0.20-0.85). The subject-specific correction factor was accurately calculated from motion of the aortic root in the coronal plane between expiratory and inspiratory breathhold (correction factor calculated from coronal image versus correction factor calculated after localization of coronary arteries, r = 0.92, p < 0.001). MRCA image quality was improved using a subject-specific correction factor, for both a 6-mm NE acceptance window (CFss versus CF0, p = 0.008; CFss versus CF1, p = 0.02) and a 16-mm NE window (CFss versus CF0, p = 0.01; CFss versus CF1, p = 0.007). Furthermore, image quality was maintained between the two NE windows if the subjects-specific correction factor was used (6 versus 16 mm, p = 0.21), with an improvement in scan efficiency (6 versus 16 mm, 49 +/- 17% versus 81 +/- 22% respectively, p < 0.001). Thus, for adaptive motion correction to be implemented, a subject-specific correction factor should be used and calculated from simple coronal expiratory and inspiratory breathholds. For real-time NE-gated cardiac MR with adaptive motion correction, the NE window can be widened to reduce the acquisition period without loss of image quality.
关于在磁共振冠状动脉造影（MRCA）中使用宽导航回波（NE）接受窗结合自适应运动校正，文献中的数据存在冲突。部分原因可能是在应用自适应运动校正算法时使用了固定校正因子，这可能会导致校正因子与平均值差异很大的受试者成像切片校正错误。我们通过测量25名受试者的上下校正因子，并评估与无自适应运动校正（CF0）和校正因子为1.0的错误自适应运动校正（CF1）相比，使用受试者特异性校正因子（CFss）进行MRCA的效果，解决了这个问题。受试者之间的校正因子差异很大（右冠状动脉近端，0.49±0.15，范围0.20 - 0.70；左冠状动脉近端，平均值0.59±0.15，范围0.20 - 0.85）。受试者特异性校正因子是根据呼气和吸气屏气之间主动脉根部在冠状面的运动准确计算得出的（从冠状图像计算的校正因子与冠状动脉定位后计算的校正因子，r = 0.92，p < 0.001）。使用受试者特异性校正因子可改善MRCA图像质量，对于6毫米NE接受窗（CFss与CF0相比，p = 0.008；CFss与CF1相比，p = 0.02）和16毫米NE窗（CFss与CF0相比，p = 0.01；CFss与CF1相比，p = 0.007）均如此。此外，如果使用受试者特异性校正因子，两个NE窗之间的图像质量得以保持（6毫米与16毫米相比，p = 0.21），扫描效率有所提高（6毫米与16毫米相比，分别为49±17%与81±22%，p < 0.001）。因此，要实施自适应运动校正，应使用受试者特异性校正因子，并通过简单的冠状呼气和吸气屏气来计算。对于具有自适应运动校正的实时NE门控心脏磁共振成像，NE窗可以加宽以缩短采集时间而不损失图像质量。
