K-SPACE ENERGY SPECTRUM ANALYSIS FOR ECHO-PLANAR IMAGING

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 *这项计划最近由R21-EB005690拨款资助给陈南贵。 *格兰特于2007年11月1日从BWH放弃给杜克大学。 摘要 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是最快的磁共振成像技术之一，已被广泛应用于各种需要高时间分辨率的动态研究中，如功能磁共振成像(FMRI)、对比增强成像和基于MR的介入治疗。然而，EPI数据质量通常会受到各种伪影的影响，如几何失真和磁化率信号丢失。此外，EPI对磁感场不均匀的敏感性使其在基于EPI的纵向研究中不太可靠。先前已经报道了几种用于EPI质量改进和伪影减少的技术。然而，以前报道的大多数EPI伪影减少方法需要耗时的野外映射扫描，因此可能并不总是实用的(例如，对于临床扫描和基于EPI的介入性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)空间相关的回波时间值，和(4)伪影水平，而不需要额外的场映射过程或脉冲序列修改。使用该方法可以有效地去除各种EPI伪影(例如失真和Gibb波纹伪影)。在此基础上，将k空间能量谱分析应用于相位编码三维并行EPI的最优捕获策略设计中，使其具有较高的信噪比和较低的运动伪影。我们还计划应用所提出的方法来重新分析先前获得的功能磁共振数据，并回溯性地提高分组激活的纵向重复性。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进他们未来基于EPI的定量研究或追溯改进以前获得的EPI数据。 [编辑] 给NCIGT带来的好处 *KESA方法可以通过可靠的相位展开过程，使用EPII提供健壮的温度图，从而有效地消除动态温度图中的相位回绕。基于我们的k空间能谱分析算法(R21项目)，我们正在设计一种新的相位映射和解缠方法。当引入新的可靠的相位展开过程时，基于MRI的温度映射将对对象的移动和敏感性效应具有更好的耐受性。因此，该项目支持我们开发新的温度映射方法的工作。 *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所做的努力。 给项目带来的好处 IGT资源为R21项目提供了必要的支持。用于序列开发的编程环境(部分地)通过来自资源的成像核心的支持来维护。此外，隶属于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助学金申请中的协作声明 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.