WIMP: SELF-NAVIGATING MAGNETIZATION TRANSFER POOL MAPPING WITH STIMULATED ECHOES

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。导言：磁化传递(MT)提供了组织中存在的结合大分子的交换率和相对数量的信息。MT已被证明在检测早期白质变性方面很有用，例如多发性硬化[6]。然而，定量MT序列需要复杂的多参数拟合。因此，序列通常仅与简单的开启或关闭共振的预脉冲相结合，由此可以计算出诸如MTR的半定量参数。然而，MT序列的这些变体并不映射纯粹的生物物理参数，并且可能被几个因素混淆。结合水池和自由水池的转移率和相对比例大小有望提供更多关于组织成分的定量信息[4]，但目前需要复杂的多参数模型和令人望而却步的长成像时间[3-5]。最近，Ropele等人。[1]介绍了一种直接测量结合大分子水含量的新方法，该方法基于调节水自旋相分布的受激回波(STE)制备方案。这些标记的自旋随后被用作本征指示剂，由于与大分子质子的磁化交换而稀释。目前，该方法仅限于单次采集，这是因为在序列的准备阶段应用了小的磁场梯度，这使得序列对整体生理运动敏感。在这项工作中，我们将利用可变密度螺旋轨迹的自导航能力[2]来准确补偿运动和相位积累，这反过来又允许更准确的BPF计算和更高的空间分辨率。参考文献：[1]Ropele等人。MRM(49)，864-871,2003[2]Liu，et al.MRM(52)，1388-1396,2004。[3]Sleed等人。MRM(46)，923-931,2001[4]Henkelman，MRM(29)，759-766,1993。[5]Yarnykh，MRM(47)，929-939,2002。[6]Tozer等人。MRM 5：83-91,2003。[7]拉马尼，核磁共振，20(10)，721-31,2002。[8]刘，MRM(54)，2005。致谢：部分工作得到了美国国立卫生研究院(1R01EB002771)、斯坦福高级磁共振技术中心(P41RR09784)、卢卡斯和橡树基金会的支持

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Magnetization transfer (MT) provides information on the rate of exchange as well as relative amount of bound macromolecules present in tissue. MT has been shown useful in detecting early white matter degeneration, such as with multiple sclerosis [6]. However, quantitative MT sequences require complex multi-parametric fits. Therefore, sequences were normally only combined with simple on or off-resonant pre-pulses, from which semi-quantitative parameters, such as MTR, can be computed. However, these variants of MT sequences do not map pure bio-physical parameters and can be confounded by several factors. Transfer rate and relative fraction sizes of bound and free water pools are expected to provide more quantitative information on tissue composition [4] but presently require complicated multi-parametric models and prohibitively long imaging times [3-5]. Recently, Ropele et al. [1] introduced a novel method that provides direct measurement of bound macromolecular water content, which is based on a stimulated echo (STE) preparation scheme that modulates the phase distribution of water spins. These labeled spins are then used as an intrinsic indicator, which dilutes due to magnetization exchange with macromolecular protons. Currently, this method is limited to single-shot acquisitions due to the application of small magnetic field gradients in the preparation phase of the sequence that renders the sequence sensitive to bulk physiologic motion. In this work, we will capitalize on the self-navigating capabilities of variable density spiral trajectories [2] to accurately compensate for motion and phase accumulation, which in turn allows a more accurate BPF calculation and higher spatial resolution. References: [1] Ropele, et al. MRM (49),864-871,2003. [2] Liu, et al. MRM (52),1388-1396,2004. [3] Sled et al. MRM (46),923-931,2001. [4] Henkelman, MRM (29),759-766,1993. [5] Yarnykh, MRM (47),929-939,2002. [6] Tozer et al. MRM 5:83-91, 2003. [7] Ramani, MRI, 20(10), 721-31, 2002. [8] Liu, MRM (54), 2005. Acknowledgements: Work was supported in part by the NIH (1R01EB002771), Center of Advanced MR Technology at Stanford (P41RR09784), Lucas and Oak Foundations