多b值DWI在儿童脑肿瘤中的初步研究

A preliminary study of pediatric brain tumors using multi-component diffusion weighted imaging

目的:探讨多b值DWI在儿童脑肿瘤中的应用价值。方法:对31例脑肿瘤患儿行EPI-DWI扫描,采用0～4000s/mm2之间的12个b值。按照单指数模型计算低b值ADC(ADClow)(b≤200s/mm2)、高b值ADC(ADChigh,200s/mm2<b≤4000s/mm2)和标准ADC(ADCstandard,0s/mm2<b≤4000s/mm2);按照双指数模型计算快ADC(ADCfast)、慢ADC(ADCslow)和ADCfast所占比例;用传统的单指数衰减模型计算b=800s/mm2时的ADC值。全部病例均经病理证实,分为低级别肿瘤组和高级别肿瘤组,比较这些参数在两组肿瘤中的鉴别诊断价值。结果:ADClow、ADChigh、ADCstandard、传统的ADC、ADCfast和ADCslow在儿童高、低级别脑肿瘤间的差异均具有显著性意义(P均<0.05)。ADCslow在高、低级别脑肿瘤间的差异最大。结论:当b值在较大范围取值时,双指数模型能反映更多儿童脑肿瘤的组织特征,代表细胞内水分子扩散的ADCslow值在儿童高、低级别脑肿瘤间差异最大,此结论尚需大样本进一步验证。

Objective：The aim of this study was to explore the value of multi-component apparent diffusion coefficients in pediatric brain tumors.Methods：31 children with brain tumors underwent brain MR scan by adopting twelve b-factors from 0 to 4000s/mm2 using EPI sequence.Firstly,using monoexponential model on three different b-factor ranges,we got low b ADC（ADClow,b≤200s/mm2）,high b ADC（ADChigh,200s/mm2b≤4000s/mm2） and the standard ADC（ADCstandard,0s/mm2b≤4000s/mm2）.Secondly,using biexponential model,we got fast ADC（ADCfast）,slow ADC（ADCslow） and the fraction of fast diffusion component.The traditional single ADC with b=800s/mm2 was also computed.All cases were confirmed by pathology and were divided into low-grade tumors and high-grade tumors.The parameters were compared between the two groups in order to evaluate their significance in differential diagnosis.Results：ADClow,ADChigh,ADCstandard,the traditional ADC,ADCfast and ADCslow between low grade and high grade brain tumors in children had significant differences（P 0.05）.The difference of ADCslow between two groups was more prominent than other parameters.Conclusion：When sampled over an extended b-factor ranges,biexponential model can provide additional tissue characteristics of pediatric brain tumors.The difference of ADCslow between the high and low grade pediatric brain tumors is the most prominent.This conclusion needs to be further proved by a large sample study.