正常人脑表观弥散系数值定量测量的方法

目的探讨最佳的弥散定量测量方法,为临床及下一步的研究提供参考。方法收集20名正常健康体检者,对其行头颅常规MRI检查及平面回波弥散加权成像（DWI）检查,获得DWI图,然后在工作站上重建表观弥散系数（ADC）图。每个研究对象选6个感兴趣区（ROI）,分别在DWI图及ADC图采用相应测量方法得到每个部位的不同成像方法的平均ADC值。结果在各相异性DWI图上通过信号强度计算的丘脑ADCM、ADCP、ADCS值差异无统计学意义（P〉0.05）,额叶白质和内囊后肢的值差异有高度统计学意义（P〈0.001）;在各相异性（同性）DWI图通过信号强度计算的丘脑、额叶白质、内囊后肢ADCave值与直接在各向异性（同性）ADC图上测量得出的ADC值差异有高度统计学意义（P〈0.001）。结论额叶白质及内囊中的水分子弥散存在各相异性,丘脑中水分子弥散是各相同性的;不同的弥散定量方法所测得的ADC值有明显差异,但以通过DWI图计算出来的ADC值较为准确,定量研究脑组织的弥散还要考虑测量方法。

Different Methods of Measuring ADC Values in Normal Human Brain

Objective To investigate better method of measuring ADC values of normal brain, and provide reference for further research. Methods Twenty healthy people＇s MR imaging were reviewed. All of them underwent routine MRI scans and echo-planar diffusion-weighted imaging （DWI）, and ADC maps were reconstructed on work station. Six regions of interest （ROI） were selected for each object, the mean ADC values were obtained for each position on DWI and ADC maps respectively.Results On the anisotropic DWI map calculated in the hypothalamus,ADCM, ADCP, ADCS values were no significant difference（P〉0.05）,in the frontal white matter and internal capsule hindlimb,there was a significant difference （P〈0.001）;on the anisotropic （isotropic） DWI map calculated through the hypothalamus, frontal white matter and internal capsule hindlimb ADCave value exist significant difference to direct measurement on the anisotropic（isotropic） ADC map（P〈0.001）. Conclusion Diffusion of water in the frontal white matter and internal capsule are anisotropic,but it is isotropic in the hypothalamus;different quantitative methods of diffusion measurement of ADC values have significant difference, but ADC values calculated through the DWI map is more accurate, quantitative diffusion study of brain tissue should also consider the diffusion measurement method.