摘要
目的:探讨磁共振扩散张量成像(DTI)时扩散梯度方向对图像质量的影响。方法:对30例健康志愿者行头部常规MRI及DTI检查。DTI检查时分别采用15、25和55这三个不同的扩散梯度方向。在右侧内囊后肢3/4处(皮质脊髓束)设定感兴趣区,测量平均扩散系数(DCavg)、部分各向异性(FA)和三个本征值(λ1、λ2、λ3),分别对3个扩散方向的DCavg和FA值进行统计学分析。使用3个本征值计算FA理论值,并与测量值进行比较。选定内囊层面的FA图,计算全层面可显示FA值<0.3的纤维束百分比,并进行统计学分析。结果:三个扩散梯度方向图像上测量的DC值差异无统计学意义(P>0.05),而FA值差异均有统计学意义(P<0.05),显示FA值<0.3的纤维束的百分比差异均有极显著性意义(P<0.01)。扩散梯度方向为15时FA测量值与理论计算值之间差异有统计学意义(P<0.05),为25和55时差异无统计学意义(P>0.05)。结论:选择扩散梯度方向为25时兼顾了图像信噪比和扫描时间,值得在临床应用中推广。
Objective:To study the influence of diffusion gradient directions on the image quality of diffuse tensor imaging (DTI). Methods:The routine MRI and DTI were performed on 30 healthy volunteers. DTI were performed with 15,25 and 55 diffusion gradient directions. DC avg, FA and eigenvalues (λ1、λ2、λ3) were measured at the three-quarter point of posterior limb of the internal capsule (corticospinal tract). Statistical analysis was obtained. Theoretic FA was calculated with 3 eigenvalues and were compared with metrical FA. The percentages of showing fasciculi with FA〈0.3 were calculated on the level of internal capsule and statistical analysis were done. Results: Among 3 diffusion gradient directions,DCavg showed no significant statistical difference (P〉 0.05), whereas, for FA, the difference of percentage of fasciculi showed significant statistical difference (P〈0.05). Significant statistical difference was existed between theoretic FA and metrical FA in 15 diffusion gradient directions,and showed no significant statistical difference in that of 25 and 55. Conclusion: Selected 25 as the diffusion gradient direction, desirable signal intensity ratio and reasonable scanning time could be obtained, which is worth recommending in clinical application.
出处
《放射学实践》
2008年第3期320-323,共4页
Radiologic Practice
关键词
磁共振成像
扩散张量成像
扩散梯度方向
图像质量
Magnetic resonance imaging
Diffusion tensor imaging
Diffusion direction
Imaging quality