扩散敏感梯度相关图像变形规律与矫正技术研究  

Study of the distortion induced by diffusion sensitive gradient and the correction technique

作　　者：韩鸿宾[1] 高东红[2] 雍涛[3] 沙琳[4] 郎宁[1] 裴新龙[1] 宋国军[5] 张海龙[2] 

机构地区：[1]北京大学第三医院放射科,北京100083 [2]北京大学公共教学部医用理学系 [3]清华大学 [4]大连医科大学附属二院 [5]包头医学院第二附属医院

出　　处：《中国医学影像技术》2004年第1期133-136,共4页Chinese Journal of Medical Imaging Technology

基　　金：为国家自然科学基金资助项目 (30 1 70 2 77)

摘　　要：目的　用坐标变换描述不同方向扩散敏感梯度 (Gb)情况下图像的变形规律 ,探讨不同方向Gb时扩散加权成像 (DWI)的变形机制矫正方法。方法　采用自制 2 5点空间定位模具 ,在三个垂直方向施加b为 10 0 0mm2 /s的Gb后采集DWIR ,S ,P,并同时获得b为 0mm2 /s的DWI0 。应用数据拟合的方法建立成像平面的坐标变换方程。利用坐标变换将DWIR ,S ,P对DWI0 进行矫正 ,再将DWI0 对标准SE T1WI进行矫正 ,定量研究其变形程度与规律。结果　相对于标准SE T1WI成像平面 ,DWI(0 ,R ,S ,P) 成像平面的变形为平面弹性变形。相对于DWI0 ,DWIR ,S,P的变形均为刚体的平行移动。DWIS 与DWIR 的变形主要表现在Y方向上的正向移动 ,以DWIS 为重 ;DWIP 表现为X与Y方向均有位移存在。各个坐标变换公式的方差分析P <0 .0 0 1,决定系数均大于 0 .99。结论　EPI的梯度回波采集方式产生的电涡流对空间定位梯度产生的影响导致图像变形为平面弹性变形。而DWI中 ,不同Gb情况下 ,具有不同的变形规律。各坐标变换公式准确定量地描述了平面成像的变形规律 ,可以用于矫正成像变形。Objective To investigate the characteristics of distortions in diffusion-weighted imagings (DWI) with diffusion-sensitizing gradients in different directions and discuss the mechanism and to study the way to correct the distortion. Methods Self-made space localization phantom with 25 points was used to study the distortion. Orthogonal DWI with b value of 1000 mm2/s and 0 mm2/s were performed. The spatial information of the phantoms on DWI was transformed to a coordinate. The correction of the misregistration was performed between DWI R,S,P with b value of 1000 mm2/s and the image with b value of 0 mm2/s, and then between DWI 0 and SE-T1WI. The characteristics of the distortion was studied quantitatively. Results With SE-T1WI as the reference frame, the distortion on EPI-DWI (0,R,S,P) was planar elastic one. The misregistration between EPI-DWI R,S,P and DWI 0 was in a translation style of rigid body. Compared with DWI 0, translation in Y direction was the main distortion on DWI Sand DWI R, while the distortion on DWI S was more severe. The distortion on DWI Pwas demonstrated as the translation in both X and Y direction. The P value in ANOVA between the analyzed coordinate equations was all less than 0.001, with R2>0.99. Conclusion The effect of eddy current induced by gradients in EPI resulted in planar elastic deformation, and the characteristics of distortion on DWI was different with Gb in different directions. The characteristics of distortion could be reflected quantitatively and accurately by the coordinate transform methods, by which methods the correction of distortion was available.

关 键 词：扩散张量成像 变形 坐标变换 矫正 

分 类 号：R318.6[医药卫生—生物医学工程] R445.2[医药卫生—基础医学]