相位编码方向对脑白质信号变化的扩散加权成像研究

Effect of phase encode directions on signal intensity of cerebral white matter with diffusion-weighted MR imaging

目的探讨不同相位编码方向(PED)扩散加权成像(DWI)中脑白质信号强度(SI)和平均表观扩散系数(ADC)值的变化。方法对12例健康成年人(年龄21～42岁,男7例,女5例)分别采用三种PED[从右到左(R■L)、从左到右(L■R)和从前到后(A■P)]进行横轴位DWI扫描(b=0、1000s/mm2),比较两侧大脑半球各叶脑白质SI和ADC值的变化,并进行配对样本t检验。结果在R■L和L■RPED的DWI中,两侧额叶(基底节层面)、颞叶脑白质SI差异具有统计学意义(P<0.05);双侧枕叶、顶叶和额叶(半卵圆中心层面)的脑白质SI差异均无统计学意义(P>0.05)。而在A■PPED的DWI中,双侧枕叶、顶叶、额叶和颞叶的脑白质SI差异均无统计学意义(P>0.05),上述各部位双侧脑白质的ADC值均无统计学差异(P>0.05)。结论 DWI中双侧脑白质信号存在差异性,较低层面额叶和颞叶脑白质信号随PED不同而变化,而ADC值不因PED变化而不同。

Objective To explore the signal intensity（SI）and average apparent diffusion coefficient（ADC） values of cerebral white matter on diffusion-weighted imaging （DWI） with different phase encode directions （PED）. Methods 12 subjects（7 men and 5 women）were chosen from a healthy population;age range from 21 to 42 years. All subjects were examined with MR imaging, including conventional and axial diffusion-weighted imaging with two b values （0 and 1000 s/mm^2） using three PEDs [ from right to left（ R L）, from left to right （L R）and from anterior to posterior（A=vP） ]. The paired-sample t test was used to compare bilateral SI and ADC values of cerebral white matter. Results On DWI with R L and L R PEDs, the SI of bilateral cerebral white matters had significant differences in the frontal lobes （ the level of the basal ganglia） and temporal lobes （ P 〈 0. 05 ）, and no significant differences （ P 〉 0.05） in both the occipital lobes, parietal lobes and frontal lobes （ the level of centrum semiovale）. However, the SI of bilateral cerebral white matter had no significant difference （ P 〉 0. 05 ） in the frontal lobe, parietal lobe, temporal lobe, occipital lobe on DWI with three PEDs, respectively, and there were no apparent ADC differences among the bilateral white matters on ADC maps （P 〉 0. 05）. Conclusions There are diffrences for the SI of the bilateral cerebral white matters, the white matter＇s SI of the lower level of frontal lobe and the temporal lobe changed together with PED,however,the ADC value is not changed with PED.