Reduced field of view MRI with rapid, B1-robust outer volume suppression
Reduced field of view MRI with rapid, B1-robust outer volume suppression
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DOI：
10.1002/mrm.23116
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发表时间：
2012-05-01
影响因子：
3.3
通讯作者：
Nayak, Krishna S.
中科院分区：
文献类型：
--
作者：
Smith, Travis B.;Nayak, Krishna S.
当所研究的解剖结构相对于受试者的全部范围较小时，MRI扫描是低效的。视野必须扩大，采集时间也相应延长。利用外部体积抑制（OVS）减少视场成像（rFOV），缩短扫描时间是可行的。外部体积抑制（OVS）是一种磁化准备序列，可以衰减感兴趣区域（ROI）外的信号。这项工作提出了一种新的OVS序列，具有圆柱形ROI，持续时间短，并且对B？1 +不均匀性。该序列由一个非选择性绝热倾降脉冲组成，它提供了B？1+-鲁棒信号抑制，和一个快速的二维螺旋圆柱形倒转脉冲。对具有横向初始磁化强度的布洛赫方程的分析揭示了小翻转角倒转脉冲的共轭对称约束。利用这一特性，可以从单发倒转脉冲中获得两发脉冲的性能。OVS序列在幻影和活体中进行了3 t多层螺旋成像验证，该序列的相对信噪比效率在幻影中为98%，在活体中为7590%。心血管rFOV成像的有效性得到了证明，与传统的全视场成像相比，它具有更高的分辨率和更少的伪影。《理性医学杂志》，2012。(c) 2011 Wiley期刊公司
MRI scans are inefficient when the size of the anatomy under investigation is small relative to the subject's full extent. The field of view must be expanded, and acquisition times accordingly prolonged. Shorter scans are feasible with reduced field of view imaging (rFOV) using outer volume suppression (OVS), a magnetization preparation sequence that attenuates signal outside a region of interest (ROI). This work presents a new OVS sequence with a cylindrical ROI, short duration, and improved tolerance for B?1+ inhomogeneity. The sequence consists of a nonselective adiabatic tipdown pulse, which provides B?1+-robust signal suppression, and a fast 2D spiral cylindrical tipback pulse. Analysis of the Bloch equations with transverse initial magnetization reveals a conjugate symmetric constraint for tipback pulses with small flip angles. This property is exploited to achieve two-shot performance from the single-shot tipback pulse. The OVS sequence is validated in phantoms and in vivo with multislice spiral imaging at 3 T. The relative signal-to-noise ratio efficiency of the proposed sequence was 98% in a phantom and 7590% in vivo. The effectiveness is demonstrated with cardiovascular rFOV imaging, which exhibits improved resolution and reduced artifacts compared to conventional, full field of view imaging. Magn Reson Med, 2012. (c) 2011 Wiley Periodicals, Inc.