磁共振成像(MRI)作为一种无创的检测手段在生物医学领域发挥着重要的作用。如何快速获得高质量的图像是MRI研究的前沿课题之一。单扫描回波平面成像是目前最常用的快速MRI技术，然而其图像易受不均匀磁场的影响而发生畸变，且分辨率和信噪比较差。本项目拟基于新近发展起来的时空编码成像技术对不均匀磁场较好的抵抗性，研究适用于不均匀磁场环境的单扫描MRI新方法。我们将系统研究时空编码MRI的技术特点，深入分析不均匀磁场下影响时空编码MRI图像分辨率和信噪比以及引起图像畸变的主要因素；结合选择激发和非线性采样等技术，设计新型单扫描时空编码MRI序列；利用压缩感知等信号处理技术实现图像的超分辨率重建，建立无参考扫描图像畸变校正方法。综合以上工作有效提高不均匀磁场下单扫描时空编码MRI图像质量，从而建立一套能够在不均匀磁场下快速获得高质量单扫描MRI图像的新方法，促进MRI在生物医学领域的应用。

Magnetic resonance imaging (MRI) is a non-invasive detection tool which plays an important role in biomedicine. How to fast achieve high-quality MRI images has been one of the frontier research topics. Currently, echo planar imaging (EPI) is the most commonly used fast MRI technique. However, EPI images are easily distorted in the presence of inhomogeneous fields, and have relatively low resolution and signal-to-noise ratio. Compared to EPI, the newly-developed spatiotemporal encoding MRI technique has better immunity to inhomogeneous fields. In this project, we will explore novel single-scan MRI methods suitable for the environment of inhomogeneous fields based on the spatiotemporal encoding technique. We will systematically investigate the characteristics of spatiotemporally encoded MRI technique and deeply analyze the main factors influencing the resolution and the signal-to-noise ratio of resulting images and causing image distortion in inhomogeneous fields. Based on the above knowledge, we will design new single-scan spatiotemporally encoded MRI pulse sequences, in combination with selective excitation and nonlinear acquisition, etc.; we will develop corresponding super-resolved reconstruction algorithms based on signal processing techniques such as compressed sensing, and set up referenceless image distortion correction method to efficiently improve the image quality. The new methods we establish will be capable of fast achieving high-quality single-scan MRI images in inhomogeneous fields. The achievements would promote the application of MRI in biomedicine.