扩散加权像变形矫正技术的相关多因素分析  

Mutilple factors analysis for the correction of the distortion on diffusion-weighted imaging

作　　者：韩鸿宾[1] 高东红[2] 

机构地区：[1]北京大学第三医院放射科,北京100083 [2]北京大学医学部生物数学与生物统计教研室,北京100083

出　　处：《中国医学影像技术》2005年第8期1271-1274,共4页Chinese Journal of Medical Imaging Technology

基　　金：国家自然科学基金资助项目(30170277)。

摘　　要：目的探讨扩散加权像变形的矫正模具位置、扩散敏感梯度大小、方向、匀场方式对扩散参数图原始图像变形的影响,为开发矫正装置与方法提供依据.方法采用自制25点空间定位模具,分别放置在环形极化线圈的中心与偏中心位置,针对每个位置(β因素),在测量前进行主动匀场,在三个垂直方向(α因素)施加b(扩散敏感系数) 为0～1000 s/mm2的Gb,b大小以100 s/mm2步进增加(γ因素).利用坐标变换得到各图的变形矫正公式,通过多因素方差分析明确各个因素与矫正公式各个系数间的关系.结果在X,Y方向的变形矫正公式如下:X=X1+X2X'+X3Y'; Y=Y1+Y2X'+Y3Y'.除X3外,各个系数均与方向(α)、位置(β)有关.刚体位移与b值有关.弹性位移与b值(γ)无关(P无显著性差异).位置(β)与b值(γ)的交互作用影响刚体位移.在扩散敏感系数在700的情况下,Gb s不引起明显的层面内位移, 而Gb r,p主要导致在Y方向的位移.模具中心匀场情况下变形最小.结论在扩散敏感系数在模具中心匀场700的情况下,Gb r,p的作用主要表现为沿相位编码方向的刚性平移.当取0～1000 s/mm2范围内的其他Gb值时,可以得到同一类型校正公式,只是刚体位移值会不同.匀场情况下,对各个DWI图像的层层对应配准是有效的变形矫正方法.Objective To study the effects of different factors on distortion in diffusion-weighted imaging （DWI）, the factors including the correction models position, the direction and the value of the diffusion sensitive coefficient, auto-or non auto-shimming. The study was proposed to provide evidents for the investigation of the correction instrument and methods. Methods Self-made space localization phantom with 25 points for correction of the distortion. The phantom was positioned in the center or off-center insides the circle polarized head coil （factor 13）. Orthogonal （factor α） DWI with b value of 0-1000 s/mm^2 （factor 7, with the incremental value of 100 s/mm^2）were performed. Data fitting were performed by using the coordinate shifting functions with the results of two formulae for the description of the distortion in X and Y direction respectively. The correction of the misregistration was performed between every DWI R,S,P images and the image with b value of 0 s/ mm^2. ANOVA was performed to clarify the correlation among different factors and every coefficient in the correction formula. Results The correction formulae along X and Y direction were presented as X= X1 ＋X2 X′＋ X3 Y′; Y= Y1＋Y2X′＋ Y3 Y′. Except X3, every coefficients had great correlation with factora and β. The rigid transition was significantly correlated with factor （γ）, while the elastic translation was not. Factor β andγhad effects on the rigid translation mutually. When b value was set 700, Gb s caused no in-plane distortion, while Gb r, p caused the in-plane rigid transition mainly along the phase-encoding diretiono DWI with the shimming center position showed the least transitions. Conclusion When b value was set 700, Gb r, p results in the rigid transition mainly along the phase-encoding direction. Under the shimming condition, for every DWIr, p images, the slice to slice registration was effective for the correction of DWI distortions.

关 键 词：扩散加权 矫正技术 多因素分析 像变形 显著性差异 矫正装置 空间定位 中心位置 垂直方向 

分 类 号：R445.2[医药卫生—影像医学与核医学] R783.3[医药卫生—诊断学]