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）的无伪影扩散标测协议，以实现临床检查中快速准确的定量扩散标测。基于EPI的弥散成像技术是一种评价生物组织微观结构的有力工具，在缺血性脑卒中、多发性硬化、肿瘤等疾病的临床检查和病理变化的检测中具有重要的应用价值。然而，基于EPI的扩散映射的准确性通常被各种EPI伪影降低，诸如奈奎斯特伪影和由于涡流引起的几何失真。在该提案中，我们的目标是进一步改进最先进的EPI伪影去除方法，并将其集成到扩散映射协议中，以使临床扫描时间不增加。该项目有三个具体目标。首先，我们计划设计技术，以消除文物扩散加权EPI，失真校正和奈奎斯特文物去除技术的基础上，我们以前开发的。其次，我们计划在不增加临床扫描时间的情况下，将已开发的伪影去除方法集成到扩散映射协议中。具体而言，将在体模上执行表征涡流相位误差（与受试者无关）的耗时程序。在临床扫描会话中，将使用修改的EPI序列仅测量受试者相关相位误差。将从体模和临床扫描中获得的相位误差信息结合起来，以有效去除伪影。最后，我们将评估8个正常受试者在3特斯拉的扩散映射协议的有效性。校正前后的伪影水平将被量化，并且校正方法在多个扫描会话中的稳定性也将被评估。本研究的成功结果将产生一个强大的和严格验证的扩散映射协议，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.