摘要
为优化扩散张量成像图像采集技术,在1.5 T磁共振扫描仪上,使用3种具有不同扩散编码梯度方向数目(NDGD)的序列成像,采用基于感兴趣区和体素的2种方法,在6个部位比较3个序列的扩散系数(〈D〉)、各向异性分数(FA)和扩散张量的本征值.另外,采用具有不同扩散敏感因子b值的序列成像,测量并探讨b值与图像信噪比和表观扩散系数的关系.结果表明,在感兴趣区水平,所有序列的〈D〉和FA及其标准差没有统计学区别,但张量本征值却有差异.在体素水平,在多数部位21-NDGD和31-NDGD序列的相关系数较高.随着b值增高,信噪比降低.当b值在一定范围内时,表观扩散系数及其标准差有不同的变化.实际中应根据不同的应用(感兴趣区或体素分析以及扩散张量成像测量参数的不同)来选择NDGD,选用b值介于400～1 300 s/mm2较为合适.
To study and optimize diffusion tensor imaging （ DTI ）acquisition techniques,in a 1.5 T magnetic resonance imaging scanner, single-shot DTI images were acquired by using three protocols with different numbers of diffusion-encoding gradient directions（ NDGD ）. DTI indices, including diffusivity （〈D〉）, fractional anisotropy （ FA ） and diffusion tensor eigenvalues, were calculated and compared with regions of interest （ ROI ） level and voxel-level methods for three protocols in six locations. In addition, DTI images were acquired with different diffusion sensitized factors b. The relationships between signal-to-noise ratio, apparent diffusion coefficient and b were analyzed. At the ROI level, no significant differences were found for 〈D〉 and FA among protocols, however, not for eigenvalues. At the voxel level, the correlation coefficient between 21-NDGD and 31-NDGD protocols was higher in most locations. Signal-to-noise ratio reduced with increased b. Apparent diffusion coefficient and its standard deviation had different change in a certain range of b. It is concluded that the selection of NDGD should depend on the different diffusion tensor imaging applications to ROI or voxel-level analyses and different diffusion tensor imaging indices, and b in the range of 400-1 300 s/mm^2 is better.
出处
《天津大学学报》
EI
CAS
CSCD
北大核心
2007年第9期1120-1127,共8页
Journal of Tianjin University(Science and Technology)
关键词
磁共振成像
扩散张量成像
采集技术
扩散编码梯度方向数目
扩散敏感因子
magnetic resonance imaging
diffusion tensor imaging
acquisition technique
number of diffusionencoding gradient direction
diffusion sensitized factor
