液体衰减反转恢复脉冲对DWI图像信噪比及ADC值的影响

Influence of FLAIR on ADC and SNR of Diffusion Weighted Imaging

目的:探讨液体衰减反转恢复(FLAIR)脉冲序列对扩散加权图像(DWI)信噪比及ADC值的影响。方法:17名健康志愿者在3.0T MRI上行常规轴位DWI和FLAIR-DWI扫描,分别测量两侧半卵圆区、扣带回、丘脑及胼胝体膝部和压部的ADC值及DWI信号强度,同时测量基底节层面的DWI信号强度作为噪声,计算以上5个部位DWI图像的信噪比。结果:扣带回和胼胝体压部的ADC值在施加FLAIR脉冲后显著下降,而半卵圆区、丘脑及胼胝体膝部在施加FLAIR脉冲前后无明显变化;5个部位的DWI图像信噪比在施加FLAIR脉冲后均显著下降(P<0.01)。结论:FLAIR显著提高了脑组织和脑脊液ADC值测量的准确性,但是也明显降低了DWI图像的信噪比。

Objective：To evaluate the influence of fluid-attenuated inversion recovery （FLAIR） preparation pulse on apparent diffusion coefficient （ADC） and signal intensity-to-noise ratio （SNR） of diffusion weighted imaging （DWI）. Methods： 17 healthy volunteers underwent axial conventional DWI and DWI with fluid attenuated inversion recovery （FLAIR-DWI） by use of the single shot echo planar diffusion weighted MR sequence in three orthogonal directions on 3.0T MR imager. The ADC and SNR of centrum semiovale,cingulate gyrus,thalamus, genu and splenium of corpus callosum were calculated separately,and were compared on both conventional DWI and FLAIR-DWI. Paired tested was used to test for statistical significance. Results.. The ADC of cingulate gyrus （t=3. 971 ,P〈0.01 ） and splenium of corpus callosum （t= 2. 537, P=0. 022） were significantly decreased after fluid attenuated inversion recovery was used, no statistic difference was seen between conventional ADC and ADC with FLAIR in centrum semiovale （t= 0. 721, P=0. 482）, genu of corpus callosum （t = 2.149, P= 0.470 ） and thalamus （t = 0.391, P = 0.703 ） ; The SNR of centrum semiovale, cingulate gyrus, thalamus, genu and splenium of corpus callosum were significantly reduced after FLAIR were used. Conclusion：FLAIR-DWI significantly improved the accurate of ADC measurements in the conjunction part of the brain tissue and the CSF,but reduced the SNR of DWI.