Wang Chunhua, Song Li, Zhang Ruzhi, Gao Fabao
Department of Radiology, West China Hospital, Sichuan University, No.37, Guoxuexiang, Chengdu, 610041, Sichuan, China.
Eur Radiol Exp. 2018 Oct 3;2(1):25. doi: 10.1186/s41747-018-0057-2.
We sought to compare diffusion tensor imaging (DTI) parameters in vivo and ex vivo in the brain and to explore the effects of radiofrequency coil and number of excitations on ex vivo DTI parameters.
Six Sprague-Dawley rat brains were used to obtain in vivo and ex vivo DTI maps with different coils and number of excitations. DTI parameters of white matter and grey matter including diffusivities, fractional anisotropy, and other dimensionless ratios (λ2/λ1, λ3/λ1, and λ2/λ3) were obtained from reconstruction maps. Comparisons of ex vivo signal-to-noise ratio with different coils and number of excitations were conducted.
Diffusivities decreased significantly after fixation in all the selected white matter and grey matter regions of interest (all at p < 0.001). The diffusivities in white matter integrity decreased more than in grey matter integrity after fixation (all at p < 0.001). The ratio of λ2/λ3 in the major brain structures changed after fixation (most at p < 0.05). There were differences in major ex vivo brain structures in DTI parameters and signal-to-noise ratio between surface coil and volume coil, and between one and four excitations (most at p < 0.05).
The impact of fixation, coil, and number of excitations on DTI parameters should be taken into consideration in clinical and experimental studies at 7.0 T.
我们试图比较大脑在体和离体状态下的扩散张量成像（DTI）参数，并探讨射频线圈和激励次数对离体DTI参数的影响。
使用6只Sprague-Dawley大鼠的大脑，通过不同的线圈和激励次数获取在体和离体DTI图谱。从重建图谱中获得白质和灰质的DTI参数，包括扩散率、分数各向异性以及其他无量纲比率（λ2/λ1、λ3/λ1和λ2/λ3）。对不同线圈和激励次数下的离体信噪比进行比较。
在所有选定的白质和灰质感兴趣区域，固定后扩散率显著降低（均p < 0.001）。固定后，白质完整性区域的扩散率下降幅度大于灰质完整性区域（均p < 0.001）。固定后，主要脑结构中λ2/λ3的比率发生变化（大多数p < 0.05）。表面线圈和容积线圈之间以及一次和四次激励之间，离体脑主要结构的DTI参数和信噪比存在差异（大多数p < 0.05）。
在7.0 T的临床和实验研究中，应考虑固定、线圈和激励次数对DTI参数的影响。
