Artifact-Free Diffusion Mapping with Echo-Planar Imaging

描述(由申请人提供)： 该项目的总体目标是开发、优化和验证基于回波平面成像(EPI)的无伪影扩散图绘制协议，以便在临床检查中实现快速准确的定量扩散图绘制。基于EPI的扩散图是评价生物组织微观结构的有力工具，在缺血性中风、多发性硬化症、肿瘤等多种疾病的临床检查和病理变化检测中具有重要价值。然而，基于EPI的扩散映射的精度通常会受到各种EPI伪影的影响，如Nyquist伪影和涡流引起的几何失真。在这个方案中，我们的目标是进一步改进最先进的EPI伪影去除方法，并将它们集成到扩散映射协议中，从而在不增加临床扫描时间的情况下进行扫描。这个项目有三个具体目标。首先，我们计划在我们之前开发的失真校正和奈奎斯特伪影去除技术的基础上，设计在扩散加权EPI中去除伪影的技术。其次，我们计划在不增加临床扫描时间的情况下，将开发的伪影去除方法集成到扩散映射协议中。具体地说，将在体模上执行表征涡流相位误差(与对象无关)的耗时过程。在临床扫描过程中，只有受试者相关的相位误差将使用修改的EPI序列进行测量。从体模和临床扫描获得的相位误差信息将被结合在一起，以进行有效的伪影去除。最后，我们将在3特斯拉的8个正常受试者上评估所开发的扩散图方案的有效性。校正前后的伪影水平将被量化，并且校正方法在多个扫描阶段上的稳定性也将被评估。这项研究的成功结果将产生一个健壮的、经过严格验证的扩散图协议，没有EPI伪影。

DESCRIPTION (provided by applicant): The overall objective of the proposed project is to develop, optimize and validate an artifact-free diffusion mapping protocol based on echo-planar imaging (EPI), to enable a fast and accurate quantitative diffusion mapping in clinical examinations. EPI based diffusion mapping is a powerful tool to assess the microstructure of the biological tissues, and is valuable in the clinical examinations and the detection of pathological changes in various diseases, such as the ischemic stroke, multiple sclerosis, and tumor. However, the accuracy of EPI based diffusion mapping is usually degraded by various EPI artifacts, such as the Nyquist artifact and geometric distortions due to the eddy current. In this proposal, we aim to further improve the state-of-the-art EPI artifact removal methods, and integrate them into a diffusion mapping protocol in such a way that the clinical scan time is not increased. This project has three specific aims. Firstly, we plan to design techniques to remove artifacts in diffusion-weighted EPI, based on the distortion correction and Nyquist artifact removal techniques we have previously developed. Secondly, we plan to integrate the developed artifact removal methods into a diffusion mapping protocol without increasing the clinical scan time. Specifically, the time-consuming procedure for characterizing the eddy current phase errors (which are subject independent) will be performed on a phantom. In the clinical scan sessions, only the subject dependent phase errors will be measured using a modified EPI sequence. The phase error information obtained from phantom and clinical scans will be combined for an effective artifact removal. Finally, we will evaluate the effectiveness of the developed diffusion mapping protocol on eight normal subjects at 3 Tesla. The levels of artifacts before and after correction will be quantified, and the stability of the correction methods over multiple scan sessions will also be evaluated. A successful outcome from this study will generate a robust and rigorously validated diffusion mapping protocol free from EPI artifacts.