O-space imaging: Highly efficient parallel imaging using second-order nonlinear fields as encoding gradients with no phase encoding.
O-space imaging: Highly efficient parallel imaging using second-order nonlinear fields as encoding gradients with no phase encoding.
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O空间成像：使用二阶非线性场作为编码梯度而无需相位编码的梯度的高效并行成像。
DOI：
10.1002/mrm.22425
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发表时间：
2010-08
影响因子：
3.3
通讯作者：
Constable, R. Todd
中科院分区：
文献类型：
--
作者：
Stockmann, Jason P.;Ciris, Pelin Aksit;Galiana, Gigi;Tam, Leo;Constable, R. Todd
最近并行成像的改进是由于使用了更多的独立表面线圈，以便最大限度地减少沿相位编码方向的混叠(S)。然而，随着线圈耦合问题开始占据主导地位，以及多个接收器链的加速增益与成本之比变得令人望而却步，增加线圈数量的收益会减少。在这项工作中，我们重新设计了空间编码策略，以提高效率，实现了一种与接收线圈提供的空间编码互补的梯度编码方案。这种方法导致了“O-空间”成像，其中梯度形状被定制到现有的表面线圈阵列，更有效地利用了包含在线圈轮廓中的空间信息。在其最简单的形式中，对于每个采集的回波，Z2球谐被用来将对象投影到几组同心圆环上，而X和Y梯度被用来在成像平面内偏移该投影。给出了O-Space编码的原理，提出了一种图像重建算法，仿真结果表明O-Space编码比SENSE成像、径向投影成像和PatLoc成像具有更高的编码效率，表明O-Space成像在加速扫描方面具有很大的潜力。
Recent improvements in parallel imaging have been driven by the use of greater numbers of independent surface coils placed so as to minimize aliasing along the phase encode direction(s). However, gains from increasing the number of coils diminish as coil coupling problems begin to dominate and the ratio of acceleration gain to expense for multiple receiver chains becomes prohibitive. In this work we redesign the spatial encoding strategy in order to gain efficiency, achieving a gradient encoding scheme that is complementary to the spatial encoding provided by the receiver coils. This approach leads to “O-Space” imaging, wherein the gradient shapes are tailored to an existing surface coil array, making more efficient use of the spatial information contained in the coil profiles. In its simplest form, for each acquired echo the Z2 spherical harmonic is used to project the object onto sets of concentric rings, while the X and Y-gradients are used to offset this projection within the imaging plane. The theory is presented, an algorithm is introduced for image reconstruction, and simulations reveal that O-Space encoding achieves high encoding efficiency compared to SENSE, radial projection imaging, and PatLoc imaging, suggesting that O-Space imaging holds great potential for accelerated scanning.
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