摘要
磁共振波谱学(MRS, Magnetic Resonance Spectroscopy)的临床应用价值在于对获得的磁共振波谱进行定量分析,MR设备采集到的FID信号经由傅立叶变换即可得到磁共振波谱,但该波谱并不具备临床参考价值,仍需要进行一系列的后处理方可获得适用于临床诊断的磁共振波谱。磁共振波谱后处理中的相位校正和涡流校正是为了获得洛仑兹线型纯吸收谱的两个重要处理过程。近年来,MRS软件包已经逐渐成为了高场磁共振设备的标准配置,因此在我公司1.5T磁共振设备上实现MRS数据采集及后处理功能已成为迫切的任务之一
本文研究了MRS系列后处理技术中的相位校正技术和涡流校正技术。主要侧重于讨论相位校正算法的优缺点和零阶涡流校正算法。在简要地阐述了磁共振成像、磁共振波谱的基本原理和磁共振波谱后处理的关键步骤后,讨论了Ernst积分法、DISPA线型分析法、PAMPAS简单积分法和熵最小化法等四种相位校正算法和零阶涡流校正算法,给出了其数学表达。本文对前两种相位校正方法和零阶涡流校正ECC法进行了实现,通过模拟数据和活体谱数据的大量分析实验,给出了上述算法的结果分析。在东软飞利浦磁共振成像系统软件Superstar基础上,本文对MRS的数据采集和后处理部分进行了软件实现。软件实现采用了面向对象的需求分析及架构设计技术,本文同时还分析了使用UML的对象建模技术对于软件系统设计开发的影响,阐述了MRS数据采集及后处理软件包的具体实现,给出了软件的业务建模、需求、分析和设计及代码示例。
实验结果表明,本文实现的两种相位校正算法很好地完成了波谱处理中对相位角修正的要求；零阶涡流校正的算法理论正确,数学推理正确,由于目前系统无法获得相应的数据,且模拟涡流影响比较困难,该部分算法代码暂时无法进行效果验证；本文实现的MRS数据采集及后处理分析软件包满足了用户的需求,可以用于我公司1.5T磁共振设备。
The clinical value of Magnetic Resonance Spectroscopy (MRS) is providing quantitative analysis to the obtained spectrum. Since the spectrum transformed from the FID which is acquired by the MR equipment via a FFT directly can not be used for clinical referencing, only after a series of Post-Processing applying to the spectrum it can be the reference to the clinical diagnosis. Recently, MRS software package has been configured as standard function in most heigh-field MRI system. Therefore, it is one of important taskes that provide MRS software package in our 1.5T scanner.
This paper discusses and expounds some methods of phase correction and eddy current correction, and it mainly describes the advantages and weaknesses of such algorithms of phase correction and eddy current correction. At beginning it gives a brief overview about basics of MRI and MRS, and the common post-processing technologies and procedure of MRS. After that, four methods of phase correction, Ernst integral, DISPA line shape, PAMPAS simple integral and entropy minimization, and zero order eddy current correction are described with mathematics of these algorithms. The first two algorithms of phase correction are realized in this paper. Based on lots of experiments, this paper has discussed the results of these algorithms. And also, this paper describes the realization of the data acquisition software and the post-processing software based on the Superstar software system. During the developing of the software, the UML symbols are used to analyse the system and describe the system. This paper also describes the benefit of OO method using UML in software developing. To describe the software architecture, the Business Model, Requirements Specification, System Use Case and Sequence Diagram of the software are given in this paper. At last, some codes of the software are given to demonstrate the design and coding phase.
Based on the result of experiment, the two algorithms of phase correction realized in this paper achieve the requirements of spectrum phase correction commendably. Because of our 1.5T scanner can not provide fid data with eddy current now, the ECC algorithm can not be verify now. The software business model, requirements, design and analysis meet the user requirements completely, and they can be used to our 1.5T scanner.
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