b值强度和数目对脑组织ADC值测定的影响

目的探讨b值强度和数目对弥散张量成像中表观弥散系数(apparentdiffusioncofficient,ADC)值测定的影响。方法使用7个不同的弥散梯度(b值分别为b0=0、b1=500s/mm2、b2=1000s/mm2、b3=1500s/mm2、b4=2000s/mm2、b5=2500s/mm2和b6=3000s/mm2)对20名正常成人脑组织进行弥散张量成像,对7个不同的b值分别进行组合(b值强度组合方式为b0b1、b0b2、b0b3、b0b4、b0b5和b0b6;b值数目组合方式为b0b6、b0b1b6、b0b1b2b6、b0b1b2b3b6、b0b1b2b3b4b6、b0b1b2b3b4b5b6)及后处理获得其ADC图,然后在ADC图上分别测定尾状核头、内囊后肢、丘脑、半卵圆中心及胼胝体膝部和压部的数值并进行统计学分析。结果脑内各个解剖部位的ADC值均随着b值强度的增加而显著降低(P<0.05);而不受b值数目的影响(P>0.05)。结论ADC值的测定受b值强度的影响,而不受b值数目的影响,在进行临床研究时要充分考虑b值强度对ADC值测定的影响。

Strength and number of b values:effects on ADC measurements of normal brain

Objective To study the effects of the strength a nd number of b values on ADC measureme nts of normal brain.Methods Seven different diffusion weightin gs were applied in twenty normal adul t brains in diffusion tensor imaging.The brain ADC maps were calculated using seven different combinations of b values based on strength(b 0 b 1 ,b 0 b 2 ,b 0 b 3 ,b 0 b 4 ,b 0 b 5 )and on numbers(b 0 b 6 .b 0 b 6 ,b 0 b 1 b 6 ,b 0 b 1 b 2 b 6 ,b 0 b 1 b 2 b 3 b 6 ,b 0 b 1 b 2 b 3 b 4 b 6 and b 0 b 1 b 2 b 3 b 4 b 5 b 6 ).The average of the ADC was measured a nd compared at the caudate nucleus,p osterior limb of the internal capsule,thalamus,centru m semiovale ,genu of corpus callosum and splenium of corpus callosum,.Re-sults The measured ADC was significantly d ecreased accompanied with increase of b values(P<0.05),but did not correlate with the b values number(P>0.05).Conclusion The strength of b values,not numbers of b value influences measurement of ADC,which should be considered in clini cal study.[