O-Space Imaging - Accelerating MRI with Z2 Gradient Encoding

描述（由申请人提供）：MRI中并行成像性能的最新改进是通过使用更多数量的射频（RF）表面线圈来驱动的，这些线圈被放置在阵列中，以便最大化解开当数据欠采样（加速）时沿线性相位编码方向沿着发生的混叠的能力。由于线圈耦合问题，随着越来越多的接收器线圈被使用，这种加速方法正在成熟并提供递减的回报，线圈耦合问题随着线圈元件的尺寸减小和元件的数量增加而占主导地位。该建议旨在通过重新评估用于空间编码的磁场梯度来进一步加速并行成像。通过考虑接收器线圈的空间编码和磁场的联合贡献，我们可以开发更有效的空间编码方法。这个问题的一个简单的解决方案是使用非线性磁场梯度，Z2梯度。这种梯度形状（相对于线性X和Y梯度）提供了与接收器线圈提供的空间编码更互补的空间编码。我们开发的方法，O空间成像-如此命名是因为读出过程中的等离子体轮廓是同心环的形状，而不是线性X读出的圆柱-最初是由我们在2010年推出的。在临床MRI扫描仪上使用小型Z2梯度插入物生成的理论和初步数据提供了证据，证明使用适量的接收器线圈可以实现加速度的大幅增加。该提案旨在使用与Siemens 3T Trio扫描仪完全集成的头部插入式Z2梯度线圈将这些测试扩展到人类成像水平。O空间成像方法是一种通用的加速方法，可以适用于几乎任何脉冲序列。我们将测试，在体模和人体成像实验中，O空间成像的能力优于传统的SENSE成像，使用修改后的自旋回波，快速自旋回波和3D成像序列在一系列的分辨率和加速因子，并使用8通道和32通道Tx/Rx线圈。这项工作的最终结果将证明这种方法的可行性。 提供高度加速的并行成像的新方法。该项目具有高度创新性，通过重新考虑空间编码梯度，它开辟了MR加速成像的新研究领域。该项目的重要性在于，为许多标准临床MR脉冲序列提供2或更大的加速因子可以为公共卫生提供巨大的好处，允许更高的分辨率或更详细的检查，并显著增加吞吐量，改善MRI的访问和/或降低每次扫描的成本。

DESCRIPTION (provided by applicant): Recent improvements in parallel-imaging performance in MRI have been driven by the use of greater numbers of radiofrequency (RF) surface coils placed in an array so as to maximize the ability to unwrap the aliasing that occurs along a linear phase encode direction when the data is undersampled (accelerated). This approach to acceleration is maturing and providing diminishing returns as more and more receiver coils are used, due to coil-coupling problems, which dominate as the size of the coil elements decreases and the number of elements increases. This proposal is aimed at providing further acceleration in parallel imaging through a reassessment of the magnetic field gradients used for spatial encoding. By considering the joint contributions of spatial encoding of the receiver coils and the magnetic fields, we can develop a more efficient approach to spatial encoding. A simple solution to this problem is to use a nonlinear magnetic field gradient, the Z2 gradient. Such a gradient shape (relative to linear X and Y gradients) provides spatial encoding more complementary to that provided by the receiver coils. The approach we have developed, O-space imaging - so named because the isofrequency contours during the readout are in the shape of concentric rings rather than columns as with a linear X-readout - was initially introduced by us in 2010. The theory and preliminary data generated using a small Z2-gradient insert on a clinical MRI scanner have provided evidence that substantial increases in acceleration can be achieved with modest numbers of receiver coils. This proposal is aimed at scaling these tests up to human imaging levels using a head-insert Z2-gradient coil fully integrated with the Siemens 3T Trio scanner. The O-space imaging approach is a general acceleration method that can be adapted to almost any pulse sequence. We will test, in phantom and human imaging experiments, the capabilities of O-space imaging to outperform conventional SENSE imaging using modified spin echo, fast spin echo and 3D imaging sequences at a range of resolutions and acceleration factors and using both an 8-channel and a 32-channel Tx/Rx coil. The end result of this work will be a demonstration of the viability of this new methodology for providing highly accelerated parallel imaging. The project is highly innovative and by reconsidering the spatial encoding gradients it opens up a new area of research in MR accelerated imaging. The project is significant in that providing an acceleration factor of 2 or more to a number of standard clinical MR pulse sequences could provide a huge benefit to public health, allowing for higher resolution, or more detailed examinations, and significantly increased throughput improving access to MRI and/or lowering per-scan costs.