Bogner Wolfgang, Hess Aaron T, Gagoski Borjan, Tisdall M Dylan, van der Kouwe Andre J W, Trattnig Siegfried, Rosen Bruce, Andronesi Ovidiu C
Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; MR Center of Excellence, Department of Radiology, Medical University Vienna, Vienna, Austria.
Department of Cardiovascular Medicine, John Radcliffe Hospital, University of Oxford Centre for Clinical Magnetic Resonance Research, Oxford, UK.
Neuroimage. 2014 Mar;88:22-31. doi: 10.1016/j.neuroimage.2013.09.034. Epub 2013 Nov 5.
The full potential of magnetic resonance spectroscopic imaging (MRSI) is often limited by localization artifacts, motion-related artifacts, scanner instabilities, and long measurement times. Localized adiabatic selective refocusing (LASER) provides accurate B1-insensitive spatial excitation even at high magnetic fields. Spiral encoding accelerates MRSI acquisition, and thus, enables 3D-coverage without compromising spatial resolution. Real-time position- and shim/frequency-tracking using MR navigators correct motion- and scanner instability-related artifacts. Each of these three advanced MRI techniques provides superior MRSI data compared to commonly used methods. In this work, we integrated in a single pulse sequence these three promising approaches. Real-time correction of motion, shim, and frequency-drifts using volumetric dual-contrast echo planar imaging-based navigators were implemented in an MRSI sequence that uses low-power gradient modulated short-echo time LASER localization and time efficient spiral readouts, in order to provide fast and robust 3D-MRSI in the human brain at 3T. The proposed sequence was demonstrated to be insensitive to motion- and scanner drift-related degradations of MRSI data in both phantoms and volunteers. Motion and scanner drift artifacts were eliminated and excellent spectral quality was recovered in the presence of strong movement. Our results confirm the expected benefits of combining a spiral 3D-LASER-MRSI sequence with real-time correction. The new sequence provides accurate, fast, and robust 3D metabolic imaging of the human brain at 3T. This will further facilitate the use of 3D-MRSI for neuroscience and clinical applications.
磁共振波谱成像（MRSI）的全部潜力常常受到定位伪影、运动相关伪影、扫描仪不稳定性以及测量时间长的限制。局部绝热选择性重聚焦（LASER）即使在高磁场下也能提供精确的对B1不敏感的空间激发。螺旋编码加速了MRSI采集，因此能够在不降低空间分辨率的情况下实现三维覆盖。使用磁共振导航器进行实时位置以及匀场/频率跟踪可校正与运动和扫描仪不稳定性相关的伪影。与常用方法相比，这三种先进的磁共振成像技术中的每一种都能提供更优质的MRSI数据。在这项工作中，我们将这三种有前景的方法集成到一个单一脉冲序列中。在一个MRSI序列中，利用基于体素双对比回波平面成像的导航器对运动、匀场和频率漂移进行实时校正，该序列采用低功率梯度调制短回波时间LASER定位和高效的螺旋读出，以便在3T条件下对人脑进行快速且稳健的三维MRSI。所提出的序列在体模和志愿者实验中均被证明对与运动和扫描仪漂移相关的MRSI数据退化不敏感。在存在强烈运动的情况下，运动和扫描仪漂移伪影被消除，并且恢复了优异的谱质量。我们的结果证实了将螺旋三维LASER - MRSI序列与实时校正相结合的预期益处。新序列在3T条件下为人脑提供了准确、快速且稳健的三维代谢成像。这将进一步促进三维MRSI在神经科学和临床应用中的使用。
