扩散张量成像评价肌萎缩侧索硬化上运动神经元损害的最适感兴趣区

Optimal Regions of Interest of MR Diffusion Tensor Imaging:Quantitative Measurements on Upper Motor Neuron of Patients with Amyotrophic Lateral Sclerosis

目的:探讨扩散张量成像(DTI)评价肌萎缩侧索硬化症(ALS)上运动神经元损害的最适感兴趣区。方法:对16例ALS患者和15例健康志愿者行常规MRI扫描和轴位DTI扫描。观察锥体束走行区的信号特点,并选取感兴趣区(ROI)测量FA值和ADC值,组间差别用t检验;各临床指标与FA、ADC值的相关性用Pearson或Spearman法。结果:在ALS组中,8例双侧内囊后肢后3/4处呈局限性T1WI略低信号及T2WI高信号(高于皮层信号);4例见双侧大脑脚、内囊后肢及侧脑室周围沿皮质脊髓束广泛分布的T2WI高信号影。在对照组中,16例均成呈局限性T1WI略低信号及T2WI略高信号(与皮层信号相等)。在内囊后肢水平,ALS组FA值明显低于对照组(t=3.452,P=0.002),ADC值明显高于对照组(t=-2.670,P=0.012);在中央前回皮层下白质,ALS组FA值有下降趋势;在中央前回皮层下白质和侧脑室周白质,ADC值有升高趋势。在半卵圆中心、大脑脚、脑桥、延髓锥体等锥体束走行区,两组间FA值和ADC值无统计学差异。内囊后肢FA值与ALS功能评分正相关(r=0.577,P=0.019),与诊断确定性呈负相关(r=-0.557,P=0.025),与年龄、病程、病情进展速度均无关;内囊后肢ADC值和以上指标均无关。结论:ALS常规MR表现与正常人间有重叠,需综合判断。ALS患者内囊后肢FA值降低和ADC值升高变化显著且稳定,前者更敏感,且与临床指标具有相关性;内囊后肢可能是量化锥体束变性的最理想部位。

Objective： To explore the optimal regions of interest of MR diffusion tensor imaging（DTI） in amyotrophic lateral sclerosis（ALS）.Methods： Sixteen patients（M∶F=9∶7,[52.1±10.0] years old） with El Escorial definite,probable,or probable-laboratory support ALS were studied.These patients were compared with 15 healthy,age and sex-matched controls（M∶F=8∶7,[50.3±10.8] years old）.The two groups were all underwent a conventional MRI and DTI sequence.DTI was performed using a single shot SE-EPI with 25 noncollinear diffusion gradient directions（b=1 000 s/mm2） on a 1.5-T MR system.For quantitative assessment of the FA and ADC,values of bilateral corticospinal tract regions were measured on all 8 regions,and statistical analysis was performed using two sample independent t-test.Correlation between diffusion parameters and various clinical variables were investigated by Pearson or Spearman correlation analysis.Results： Focal slight low signal intensity on T1WI and high signal intensity（hyperintense to gray matter） on T2WI was demonstrated in 8 ALS cases（53.3%） in bilateral posterior limb of internal capsule（PIC）.More extensive corticospinal tract abnormality,including the periventricular white matter,the PIC,and the cerebral peduncle,was detected in 4 ALS cases（26.7%）.In control group,the focal slight low signal intensity on T1WI and slight high signal intensity（isointense to gray matter） on T2WI was demonstrated in all 16 subjects in bilateral PIC.A significant reduction in fractional anisotropy（FA）（t=3.452,P=0.002） and increase in the average diffusion coefficient（ADC） was found（t=-2.670,P=0.012） on the level of posterior limb of internal capsule in ALS group.Although there was a trend towards reduced FA and elevated ADC on the level of the subcortical white matter（SWM） of precentral gyrul in ALS group,this did not reach to statistical significance.The FA correlated with measures of disease severity（evaluated with ALSFRS）,but no correlations were found between clinical markers of disability and ADC.Conclusion： Clinical information must be considered when diagnosing ALS by using conventional MR imaging.The diffusion tensor MRI can noninvasively detect and assess corticospinal tracts and its potential disorder in vivo,thus providing useful information in diagnosing and further understanding ALS.The PIC region is potentially useful as a optimal region of interest for monitoring the progression of uper motion neuron pathology.