Diffusion Weighted Imaging with Circularly Polarized Oscillating Gradients
Diffusion Weighted Imaging with Circularly Polarized Oscillating Gradients
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DOI：
10.1002/mrm.25211
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发表时间：
2015-03-01
影响因子：
3.3
通讯作者：
Dyrby, Tim B.
中科院分区：
文献类型：
--
作者：
Lundell, Henrik;Sonderby, Casper Kaae;Dyrby, Tim B.
目的短扩散时间机制为组织微观结构提供了一种有趣的探针，并且可以通过振荡梯度自旋回波（OGSE）实验进行研究。几项研究报告了临床前环境中的新对比，并且最近提出了第一个体内人体实验。实际实现中的一个主要障碍是在梯度强度有限的高频下提供的低有效扩散权重。理论作为OGSE低扩散权重的解决方案，引入了圆偏振OGSE（CP-OGSE）。 CP-OGSE 通过在平面而不是在一个方向上进行编码，使扩散权重增加了一倍。 CP-OGSE 可用于各向异性组织的旋转不变采集。方法在死后猴脑上使用 4.7 T 临床前扫描仪进行实验，并使用传统 OGSE 和 CP-OGSE 进行模拟。结果模拟和实验表明 CP-OGSE 提供与 OGSE 相同的微观结构信息，但在有限的梯度强度下提供更稳健的参数估计。结论 CP-OGSE 可以为OGSE 成像在梯度强度有限的临床成像环境中更有效。此外，改进的扩散加权也可用于扩大研究的频率范围。 Magn Reson Med 73:1171-1176, 2015。(c) 2014 Wiley periodicals, Inc.
PurposeThe short diffusion time regime provides an interesting probe for tissue microstructure and can be investigated with oscillating gradient spin echo (OGSE) experiments. Several studies report new contrasts in preclinical settings and the first in vivo human experiments have recently been presented. One major hurdle in practical implementation is the low effective diffusion weighting provided at high frequency with limited gradient strength.TheoryAs a solution to the low diffusion weighting of OGSE, circularly polarized OGSE (CP-OGSE) is introduced. CP-OGSE gives a twofold increase in diffusion weighting with encoding in a plane rather than in one direction. CP-OGSE can be used for rotationally invariant acquisitions on anisotropic tissues.MethodsExperiments with a 4.7 T preclinical scanner on a postmortem monkey brain as well as simulations were performed using conventional OGSE and CP-OGSE.ResultsSimulations and experiments show that CP-OGSE provides the same microstructural information as OGSE but provides more robust parameter estimates with limited gradient strength.ConclusionsCP-OGSE can be an important contribution for making OGSE imaging more effective in clinical imaging settings with limited gradient strength. Furthermore, the improved diffusion weighting can also be used to expand the investigated frequency range. Magn Reson Med 73:1171-1176, 2015. (c) 2014 Wiley Periodicals, Inc.