Bilgen Mehmet, Al-Hafez Baraa, Malone Thomas M, Smirnova Irina V
Hoglund Brain Imaging Center, The University of Kansas Medical Center, Kansas City, KS 66160, USA.
Magn Reson Imaging. 2005 May;23(4):601-5. doi: 10.1016/j.mri.2005.02.003.
The magnetic resonance (MR) properties of the rat spinal cord were characterized at the T9 level with ex vivo experiments performed at 9.4 T. The inherent endogenous contrast parameters, proton density (PD), longitudinal and transverse relaxation times T1 and T2, and magnetization transfer ratio (MTR) were measured separately for the grey matter (GM) and white matter (WM). Analysis of the measurements indicated that these tissues have statistically different proton densities with means PD(GM)=54.8+/-2.5% versus PD(WM)=45.2+/-2.4%, and different T1 values with means T1GM=2.28+/-0.23 s versus T1WM=1.97+/-0.21 s. The corresponding values for T2 were T2GM=31.8+/-4.9 ms versus T2WM=29.5+/-4.9 ms, and the difference was insignificant. The difference between MTR(GM)=31.2+/-6.1% and MTR(WM)=33.1+/-5.9% was also insignificant. These results collectively suggest that PD and T1 are the two most important parameters that determine the observed contrast on spinal cord images acquired at 9.4 T. Therefore, in MR imaging studies of spinal cord at this field strength, these parameters need to be considered not only in optimizing the protocols but also in signal enhancement strategies involving exogenous contrast agents.
通过在9.4T磁场下进行的离体实验，对大鼠脊髓T9水平的磁共振（MR）特性进行了表征。分别测量了灰质（GM）和白质（WM）的固有内源性对比参数，即质子密度（PD）、纵向和横向弛豫时间T1和T2，以及磁化传递率（MTR）。测量分析表明，这些组织的质子密度在统计学上存在差异，灰质平均质子密度PD(GM)=54.8±2.5%，白质平均质子密度PD(WM)=45.2±2.4%；T1值也不同，灰质平均T1GM=2.28±0.23秒，白质平均T1WM=1.97±0.21秒。T2的相应值分别为T2GM=31.8±4.9毫秒和T2WM=29.5±4.9毫秒，差异不显著。MTR(GM)=31.2±6.1%与MTR(WM)=33.1±5.9%之间的差异也不显著。这些结果共同表明，PD和T1是决定在9.4T磁场下获取的脊髓图像中观察到的对比度的两个最重要参数。因此，在该场强下进行脊髓的磁共振成像研究时，不仅在优化成像方案时，而且在涉及外源性对比剂的信号增强策略中，都需要考虑这些参数。
