Cukur Tolga, Nishimura Dwight G
Department of Electrical Engineering, Stanford University, Stanford, CA 94305-9510, USA.
Magn Reson Med. 2009 Jul;62(1):193-204. doi: 10.1002/mrm.21990.
Although balanced steady-state free precession (bSSFP) imaging yields high signal-to-noise ratio (SNR) efficiency, the bright lipid signal is often undesirable. The bSSFP spectrum can be shaped to suppress the fat signal with scan-efficient alternating repetition time (ATR) bSSFP. However, the level of suppression is limited, and the pass-band is narrow due to its nonuniform shape. A multiple repetition time (TR) bSSFP scheme is proposed that creates a broad stop-band with a scan efficiency comparable with ATR-SSFP. Furthermore, the pass-band signal uniformity is improved, resulting in fewer shading/banding artifacts. When data acquisition occurs in more than a single TR within the multiple-TR period, the echoes can be combined to significantly improve the level of suppression. The signal characteristics of the proposed technique were compared with bSSFP and ATR-SSFP. The multiple-TR method generates identical contrast to bSSFP, and achieves up to an order of magnitude higher stop-band suppression than ATR-SSFP. In vivo studies at 1.5 T and 3 T demonstrate the superior fat-suppression performance of multiple-TR bSSFP.
尽管平衡稳态自由进动（bSSFP）成像具有较高的信噪比（SNR）效率，但明亮的脂质信号通常并不理想。bSSFP谱可以通过扫描效率高的交替重复时间（ATR）bSSFP来塑形以抑制脂肪信号。然而，抑制水平有限，并且由于其形状不均匀，通带较窄。提出了一种多重重复时间（TR）bSSFP方案，该方案可创建一个宽阻带，其扫描效率与ATR-SSFP相当。此外，通带信号均匀性得到改善，从而减少了阴影/条纹伪影。当在多重TR周期内的单个TR以上进行数据采集时，可以组合回波以显著提高抑制水平。将所提出技术的信号特征与bSSFP和ATR-SSFP进行了比较。多重TR方法产生与bSSFP相同的对比度，并且实现了比ATR-SSFP高一个数量级的阻带抑制。在1.5 T和3 T场强下的体内研究证明了多重TR bSSFP具有卓越的脂肪抑制性能。
