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

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。简介：磁化转移（MT）提供了交换速率以及组织中存在的结合大分子的相对量的信息。MT已被证明可用于检测早期白色物质变性，如多发性硬化症[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或关谐振预脉冲组合，从中可以计算半定量参数，例如MTR。然而，MT序列的这些变体不能映射纯生物物理参数，并且可能被几个因素混淆。预计结合和游离水池的转移速率和相对分数大小可提供关于组织组成的更多定量信息[4]，但目前需要复杂的多参数模型和过长的成像时间[3-5]。最近，Ropele等人。[1]介绍了一种新的方法，该方法提供了对结合大分子水含量的直接测量，该方法基于调制水自旋相位分布的受激回波（STE）制备方案。这些标记的自旋然后被用作内在指示剂，其由于与大分子质子的磁化交换而稀释。目前，由于在序列的准备阶段应用小磁场梯度，使得序列对整体生理运动敏感，因此该方法仅限于单次激发采集。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]来精确地补偿运动和相位累积，这反过来又允许更精确的BPF计算和更高的空间分辨率。 参考文献：[1] Ropele，et al. MRM（49），864 - 871，2003. [2]Liu等，MRM（52），1388 - 1396，2004. [3]Sled等，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]Ramani，MRI，20（10），721-31，2002. [8]Liu，MRM（54），2005.鸣谢：这项工作得到了NIH（1 R 01 EB 002771）、斯坦福大学高级MR技术中心（P41 RR 09784）、Lucas和Oak基金会的部分支持

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