基于k空间椭圆中心轨迹的三维时间飞跃法血管成像双回波序列设计

发布时间：2018-04-17 21:17

本文选题：椭圆中心轨迹 + 三维时间飞跃法　；参考：《杭州电子科技大学》2017年硕士论文

【摘要】：近年来,随着磁共振成像技术在科学研究和临床应用上的不断发展,新技术,新方法层出不穷,用于解决传统扫描方式的长扫描时间,低图像信噪比等问题。而本文的工作就是对传统的三维时间飞跃法血管成像序列的一个改进。在传统的时间飞跃法血管成像序列中,高信噪比,高对比度,高分辨率的血管图像需要耗费较长的扫描时间,并且施加在相位以及读出方向的流动补偿梯度会导致回波时间(echo time,TE)的增加。针对上述问题,本文提出了基于k空间椭圆中心轨迹的三维时间飞跃法血管成像双回波序列的设计方法,与传统的三维时间飞跃血管成像单回波序列相比,其有效回波时间缩短了0.7ms,并且扫描时间减少了61%。为评价本序列的合理性和有效性,本文对该序列进行了详细的解释,并与相关的序列进行了比较。同时,通过采用各个序列对人体大脑进行数据采集,然后定量地测量血管的对比度噪声比(contrast to noise ratio,CNR)来验证该序列的可行性。主要的工作包括:(1)传统的三维时间飞跃法血管成像双回波序列的设计传统的三维时间飞跃法血管成像双回波序列的设计是在传统的三维时间飞跃法血管成像单回波序列的基础上进行的改进,其中传统单回波序列主要采用了短的不对称射频激发脉冲,最小持续时间梯度,以及部分回波采集。针对单回波序列循环过程中的冗余时间,在一个循环过程引入额外的相位编码梯度和读出回波梯度,有效地将k空间填充时间减少一半,从而实现传统三维时间飞跃法血管成像双回波序列设计。序列的设计是通过在联影医疗科技有限公司的开发平台ADEPT上进行C++语言的编写来实现。(2)基于k空间椭圆中心轨迹的三维时间飞跃法血管成像双回波序列的设计基于k空间椭圆中心轨迹的三维时间飞跃法血管成像双回波序列的设计同样是在传统的三维时间飞跃法血管成像单回波序列的基础上,通过重新设计k空间的遍历方式进行添加修改。其中k空间的遍历轨迹的设计是通过MATLAB软件实现,然后通过C++语言写入序列开发平台。(3)人体大脑韦利斯环区域的数据采集及成像序列的可行性需要通过实际的临床效果来进行验证。通过选择合适的参数,对五位健康人体被试的大脑韦利斯环区域进行数据采集,并且对于不同的序列方法采集到的图像进行定性和定量上的分析。衡量图像的优劣性主要通过两种方式,1)直观地观察图像,是否有血管缺失以及其他伪影;2)定量地测量某些重要血管的CNR值。上述实验都是基于联影医疗科技有限公司的1.5T核磁共振扫描仪器上,对健康人体大脑的韦利斯环区域进行成像。最终的结果表明,(1)相比与传统的三维时间飞跃法血管成像单回波序列,虽然本序列的血管图像的CNR值降低了2.5%,但扫描时间减少了约61%,且回波时间进一步地缩短了0.7ms。而当将本序列进行重复采集平均后(两次采集的总扫描时间比传统的单回波扫描时间少了22%)的结果与传统单回波序列相比,本序列的CNR值提高了54.3%;(2)相比与传统的三维时间飞跃法血管成像双回波序列,本序列的优点体现在:1)扫描时间减少了22%,2)CNR值提高了10.9%,3)由于双回波调制引入的伪影减少。
[Abstract]:In recent years, with the continuous development of the technology of magnetic resonance imaging, in the scientific research and clinical application of the new technology, new method is used to solve the long scan time emerge in an endless stream, the traditional scanning method, low image SNR. And 3D time-of-flight angiography sequences of the traditional is the work of an improvement. At the time of flight angiography sequence in the traditional, high signal-to-noise ratio, high contrast, high resolution scanning time vascular image takes longer, and applied in the readout direction gradient flow compensation phase and cause the echo time (echo time, TE) increased. In view of the above problems, this paper puts forward the design method of 3D TOF angiography of ellipse center K space trajectory based on double echo sequence, compared with the 3D TOF angiography traditional single echo sequence, the effective echo time reduction Short 0.7ms, and the scan time is reduced by 61%. for the evaluation of the sequence of rationality and validity, this paper gives a detailed explanation of the sequence, and compared with the related sequence. At the same time, through the data acquisition of the human brain using various sequences, then quantitative measurements of blood vessels in contrast to noise ratio (contrast to noise ratio, CNR) to verify the feasibility of the series. The main work includes: (1) design of 3D TOF angiography design of traditional TOF angiography in traditional double echo sequence double echo sequence is improved based on 3D TOF angiography in traditional single echo sequence on the traditional single echo sequence mainly adopts asymmetric RF short excitation pulse duration, minimum gradient, and echo acquisition. For the single echo sequence cycle The redundancy time, introducing additional phase encoding gradient in a cyclic process and readout echo gradient, K space filling time can be effectively reduced by half, to achieve the traditional 3D time-of-flight angiography double echo sequence. The sequence design design is written in C++ language to achieve the ADEPT development platform in the movie Medical Technology Co. the company. (2) based on the design of 3D TOF angiography of ellipse center trajectory K space double echo sequence design based on 3D time-of-flight angiography of ellipse center trajectory K space double echo sequence is also based on 3D time-of-flight angiography in traditional single echo sequence, add modify the way by traversing the re design of the K space. The design of the K space trajectory traversal is realized by MATLAB software, and then through the C++ language write sequence Development platform. (3) the feasibility of human brain Willis ring region sequence data acquisition and imaging through the actual clinical effect need to verify. By choosing appropriate parameters, collect the data of five healthy human subjects brain Willis Circle area, and the qualitative and quantitative analysis on different sequences methods collected images. The image quality measure mainly through two ways: 1) to visually observe image, whether there is lack of blood vessels and other artifacts; 2) to quantitatively measure some important vascular CNR value. The experiment is based on the 1.5T magnetic resonance scanner movie Medical Technology Company Limited. The imaging area of the circle of Willis, healthy human brain. The final results show that (1) compared with the TOF angiography traditional single echo sequence, although the vascular image sequence The CNR value decreased by 2.5%, but the scan time is reduced by about 61%, and the echo time further shortened when the 0.7ms. sequence was repeated after the average acquisition (two acquisition of the total scanning time were 22% less than the traditional single echo scanning time) the results of traditional single echo sequence in the sequence the CNR value increased by 54.3%; (2) compared with the TOF angiography of traditional double echo sequence, the sequence of advantages embodied in: 1) the scan time is reduced by 22%, 2) CNR value increased by 10.9%, 3) due to artifacts of dual echo modulation is introduced to reduce.

【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R445.2;TP391.41

【参考文献】