Snyder Angela L S, Corum Curtis A, Moeller Steen, Powell Nathaniel J, Garwood Michael
Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota School of Medicine, Minneapolis, Minnesota, USA.
Magn Reson Med. 2014 Jul;72(1):49-58. doi: 10.1002/mrm.24888. Epub 2013 Aug 1.
This work introduces a technique to excite MR signals locally and to steer this localized region over the object in a spatiotemporal manner. The purpose is to demonstrate the feasibility of MRI with multidimensional spatiotemporal-encoding in a way that provides the ability to compensate extreme field inhomogeneity.
The method is called steering resonance over the object (STEREO). A modulated gradient is applied in concert with a frequency-modulated pulse to steer a resonant region through space and thus produce sequential excitation and echo formation. Images are reconstructed using exclusively an inverse problem solution.
Images of phantoms and human brain were produced to demonstrate the feasibility of the STEREO sequence and image reconstruction. Simulations support the postulated capability to compensate for extreme field inhomogeneity.
STEREO represents a substantial departure from conventional MRI in which spins contained in the sample, slab, or slice are excited synchronously. By exciting spins sequentially along a curved spatial trajectory, STEREO in principle affords a unique opportunity to adjust for spatial variations in static and radiofrequency fields. By adjusting field amplitudes and frequencies in a temporal manner in STEREO, in future works it should be possible to perform MRI with highly inhomogeneous fields.
本研究介绍了一种局部激发磁共振信号并以时空方式在物体上操纵该局部区域的技术。目的是以一种能够补偿极端场不均匀性的方式，证明多维时空编码磁共振成像的可行性。
该方法称为物体上的操纵共振（STEREO）。将调制梯度与调频脉冲协同应用，以在空间中操纵共振区域，从而产生顺序激发和回波形成。仅使用逆问题解决方案重建图像。
生成了体模和人脑的图像，以证明STEREO序列和图像重建的可行性。模拟结果支持了补偿极端场不均匀性的假设能力。
STEREO与传统的磁共振成像有很大不同，传统磁共振成像中样本、板层或切片中包含的自旋是同步激发的。通过沿弯曲的空间轨迹顺序激发自旋，STEREO原则上提供了一个独特的机会来调整静态和射频场中的空间变化。通过在STEREO中以时间方式调整场幅度和频率，在未来的工作中应该有可能在高度不均匀的场中进行磁共振成像。
