Schär Michael, Kozerke Sebastian, Fischer Stefan E, Boesiger Peter
Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
Magn Reson Med. 2004 Apr;51(4):799-806. doi: 10.1002/mrm.20024.
Balanced steady-state free precession (SSFP) techniques provide excellent contrast between myocardium and blood at a high signal-to-noise ratio (SNR). Hence, SSFP imaging has become the method of choice for assessing cardiac function at 1.5T. The expected improvement in SNR at higher field strength prompted us to implement SSFP at 3.0T. In this work, an optimized sequence protocol for cardiac SSFP imaging at 3.0T is derived, taking into account several partly adverse effects at higher field, such as increased field inhomogeneities, longer T(1), and power deposition limitations. SSFP contrast is established by optimizing the maximum amplitude of the radiofrequency (RF) field strength for shortest TR, as well as by localized linear or second-order shimming and local optimization of the resonance frequency. Given the increased SNR, sensitivity encoding (SENSE) can be employed to shorten breath-hold times. Short-axis, long-axis, and four-chamber cine views obtained in healthy adult subjects are presented, and three different types of artifacts are discussed along with potential methods for reducing them.
平衡稳态自由进动（SSFP）技术在高信噪比（SNR）下能在心肌和血液之间提供出色的对比度。因此，SSFP成像已成为1.5T场强下评估心脏功能的首选方法。更高场强下预期的信噪比提升促使我们在3.0T场强下实施SSFP成像。在这项工作中，考虑到更高场强下的一些部分不利影响，如场不均匀性增加、T(1)延长和功率沉积限制，推导了一种用于3.0T场强下心脏SSFP成像的优化序列方案。通过针对最短TR优化射频（RF）场强的最大幅度，以及通过局部线性或二阶匀场和共振频率的局部优化来建立SSFP对比度。鉴于信噪比的提高，可以采用灵敏度编码（SENSE）来缩短屏气时间。展示了在健康成年受试者中获得的短轴、长轴和四腔电影视图，并讨论了三种不同类型的伪影以及减少它们的潜在方法。
