回波时间对脑组织弥散张量成像定量指标的影响

Effect of echo time on the quantification of diffusion tensor imaging of brain at 3.0T

目的研究回波时间对脑弥散张量成像定量指标有无影响。方法对7只健康成年恒河猴用3.0T磁共振设备行弥散张量成像（DTI）。在固定其他参数的情况下改变回波时间（75～160ms,共13个采样点）。选择双侧内囊后肢和壳核分别作为白质和灰质感兴趣区（region of interest,ROI）。并测量该ROI内的平均弥散率（mean diffusivity,MD）,分数各向异性（fractional anisotropy,FA）,最大本征值（λ1）,中间本征值（λ2）和最小本征值（λ3）。使用Pearson回归分析这些弥散指标与回波时间（TE）的线性关系。结果恒河猴脑灰质区MD与TE正相关（P〈0.001）,白质区MD与TE相关性不显著（P〉0.05）。两ROI内的FA和λ1均与TE正相关,λ3与TE负相关（P〈0.001）。灰质区λ2与TE正相关,而白质区λ2与TE负相关（P〈0.001）。结论回波时间可影响DTI定量指标的测量。在临床多中心研究中,需要对之进行控制。

Objective To investigate the effects of echo time（TE）on diffusion tensor quantification of brain.Methods Seven Macaca mulatta underwent diffusion tensor MR imaging（DTI）with a series of TEs at 3.0T MR scanners.The diffusion scalars including mean diffusivity（MD）,fractional anisotropy（FA）,and eigenvalues（λ1,λ2 and λ3）were measured in the region of interest（ROI）at the bilateral posterior limb of internal capsule and the putamen.Pearson correlation coefficients were used to test the relationships between TE and the diffusion scalars.Results The MD showed positive correlation with TE in gray matter（GM）（P〈0.001）but not in white matter（WM）（P〉0.05）.Both the FA and λ1 of GM and WM were positively correlated with TE（P〈0.001）.The λ2 of GM increased and λ2 of WM decreased with increasing TE.And the λ3 were negatively correlated with TE.Conclusion TE may influence the quantification of diffusion tensor imaging,which should be controlled in multi-center studies.