K-SPACE ENERGY SPECTRUM ANALYSIS FOR ECHO-PLANAR IMAGING

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。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。列出的机构是 中心，不一定是研究者的机构。 * 该项目最近在R21-EB 005690赠款下资助给Nan-kuei Chen。 * 格兰特于2007年11月1日从BWH放弃到杜克大学。 总结 本项目的目标是提高回波平面成像（EPI）的质量和空间精度，以便从基于EPI的医学研究和临床诊断中获得准确的定量信息。EPI是最快的MR成像技术之一，并已广泛应用于各种需要高时间分辨率的动态研究，如功能MRI（fMRI），对比增强成像和基于MR的介入手术。然而，EPI数据质量通常会因各种伪影而降低，例如几何失真和磁化率信号丢失。此外，EPI对磁化场不均匀性的敏感性使其在基于EPI的纵向研究中不太可靠。先前已经报道了用于EPI质量改进和伪影减少的几种技术。然而，大多数先前报告的EPI伪影减少方法需要耗时的场映射扫描，因此可能并不总是实用的（例如，对于临床扫描和基于EPI的介入MRI程序）。在这里，我们建议使用一种新的k空间能量谱分析来量化（1）k空间能量分布，（2）磁化率场梯度，（3）空间相关回波时间值，以及（4）直接来自采集的EPI数据的伪影水平，而不需要额外的场映射过程或脉冲序列修改。使用所提出的方法可以有效地去除各种EPI伪影（例如失真和吉布涟漪伪影）。此外，开发的k空间能量谱分析将被应用于设计相位编码的3D并行EPI的最佳采集策略，具有改善的信噪比和减少的运动相关伪影。我们还计划应用所提出的方法来重新分析以前获得的fMRI数据，并回顾性地提高分组激活的纵向可重复性。在拟议项目中开发的方法将提供给MRI社区，以便其他研究小组可以使用开发的方法来改善他们未来基于EPI的定量研究或回顾性改善以前获得的EPI数据。 [编辑] 对NCIGT的好处 * KESA方法可以应用于通过可靠的相位展开过程使用EPII提供鲁棒的温度图，以有效地消除动态温度映射中的相位缠绕。基于我们的K空间能谱分析算法（R21项目），设计了一种新的相位映射和展开方法。当包括新的可靠相位展开程序时，基于MRI的温度映射将具有对受试者移动和敏感性效应的更好的耐受性。因此，该项目支持我们在开发新的温度映射方法方面的工作。 * 使用KESA方法的场图可用于基于EPI的fMRI和DTI中的失真校正。因此，这项工作支持我们在神经外科核心的努力。 对项目的好处 IGT资源为R21项目提供了必要的支持。序列开发的编程环境（部分）通过资源成像核心的支持进行维护。此外，IGT资源的培训研究员吴明龙正在参与R21项目的实验工作。 [编辑] U41资助申请合作声明 这个R21项目没有包括在最初的赠款申请中，因为它从那时起就得到了资助。

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. * This project was recently funded under grant R21-EB005690 to Nan-kuei Chen. * Grant relinquished from BWH to Duke University as of November 1, 2007. Summary The goal of this project is to improve the quality and spatial accuracy of echo-planar imaging (EPI), so that accurate quantitative information can be derived from EPI based medical research and clinical diagnosis. EPI is one of the fastest MR imaging techniques, and has been popularly applied to various dynamic studies that require high temporal-resolution, such as functional MRI (fMRI), contrast-enhanced imaging, and MR based interventional procedures. However, EPI data quality is usually degraded by various artifacts, such as geometric distortions and susceptibility signal loss. Furthermore, the sensitivity of EPI to susceptibility field nhomogeneities makes it less reliable in EPI based longitudinal studies. Several techniques have been previously reported for EPI quality improvement and artifact reduction. However, most previously reported EPI artifact reduction methods require time-consuming field mapping scans, and therefore may not always be practical (e.g. for clinical scans and EPI based interventional MRI procedures). Here we propose to use a novel k-space energy spectrum analysis to quantify (1) the k-space energy distribution, (2) susceptibility field gradients, (3) the spatially-dependent echo time values, and (4) artifact levels directly from the acquired EPI data, without the need of additional field mapping procedure or pulse sequence modification. Various EPI artifacts (e.g. distortions and Gibb's ripple artifact) can be effectively removed using the proposed approach. Furthermore, the developed k-space energy spectrum analysis will be applied to design an optimal acquisition strategy for phase-encoded 3D parallel EPI, with an improved signal-to-noise ratio and reduced motion related artifact. We also plan to apply the proposed methods to re-analyze the previously acquired fMRI data, and retrospectively improve the longitudinal reproducibility of grouped activation. The methods developed in the proposed project will be made available to MRI community so that other research groups may use the developed methods to improve their future EPI based quantitative studies or to retrospectively improve the EPI data that were previously obtained. [edit] Benefits to NCIGT * The KESA method can be applied to provide robust temperature maps using EPII through reliable phase unwrapping procedure to effectively eliminate the phase wraparounds in dynamic temperature mapping. Based on our k-space energy spectrum analysis algorithm (R21 project), a new phase mapping and unwrapping method is being designed. The MRI based temperature mapping will have a better tolerance to subject movement and susceptibility effect when the new reliable phase unwrapping procedure is included. Thus, this project supports our work in the development of new temperature mapping methods. * Field maps using the KESA method can be used for distortion correction in EPI-base fMRI and DTI. Thus this work supports our efforts in the Neurosurgery Core. Benefits to the Project The IGT resource provides an essential support to the R21 project. The programming environment for development of the sequence is maintained (in part) through support from the imaging core of the resource. In addition, a training fellow attached to the IGT resource, Ming-Long Wu, is participating in the experimental work of the R21 project. [edit] Statement of the Collaboration in the U41 Grant Application This R21 project was not included in original grant application because it has been funded since then.