膝关节软骨损伤的MR三维重建实验研究

An Experimental Study of Articular Cartilage Injury in the Knee with Three Dimensional MR Reconstruction

目的 通过对关节软骨损伤的动物标本和MR三维及二维图像的精确测量，观察MR三维重建图像显示关节软骨损伤病变的能力及测量病变大小的准确性。材料与方法 采用新鲜猪膝关节，以外科方法制作2～4级的关节软骨损伤标本并进行MR扫描，最后在工作站对图像进行二维和三维重建并测量，与标本的实际测量结果相对照。结果 按照1mm、1．5mm、3mm扫描层厚分组，3、4级损伤的表面遮盖显示（SSD）三维重建图像测量值的平均百分误差比较结果：X^2=74．45，P〈0．01。SSD和最大信号强度投影（MIP）两种三维重建方式测量误差的差异经Fdedman Test检验具有统计学意义（X^2=8．65，P=0．013〈0．05）。对三组测量值进行方差分析，其差异具有显著的统计学意义（F=16．601，P〈0．01）。SSD三维重建图像对4级损伤测量的百分误差最小。对3、4级损伤测量值进行Mann-Whitney U检验，其差异具有统计学意义（Z=-2．24，P=0．025〈0．05）。测量关节软骨病变大小在1mm扫描层厚的SSD三维重建图像上较二维磁共振图像更为准确。采用随机区组秩和检验的Friedman Test（X^2=8．65，P=0．013〈0．05）。结论 三维重建测量误差的大小与MR扫描层厚三维重建方式、损伤区的大小和关节软骨损伤的程度等有关。关节软骨的三维重建图像能够较真实地反映关节软骨表面的不规则形态，测量线的方向不受扫描平面方向的限制，可以对任意两点间的距离进行测量。

Objective To assess the accuracy of three dimensional MBrecoostrucfion in the diagnosis of articular cartilage lesioos, using actual cartilage specimens as reference standards. Materials and Methods 5 freshly slaughtered porcine knees was used in this articular carthage study. Articular cartilage injuries of grade Ⅱ , grade Ⅲ and grade Ⅳ were created on articular surfaces of the five porcine knee joints. The 5 porcine knees were performed MR scan to be measured on 2D or 3D MR reconstruction by workstation, and results were compared to the actual measurement. Results All the specimens were divided into three groups （1mm, 1.5mm, 3mm）, and results of measurement on Ⅲ and Ⅳ grade of cartilage injury by SSD reconstruction way were （X^2 = 74.45, P 〈 0.01 ）. Friedman Test was performed to evaluate the difference between SSD and MIP ,and showed a statistical difference （X^2 = 8.65, P = 0.013 〈 0.05） . With the SSD reconstruction way the lesions were measured more accurately in the Ⅳ grade of cartilage injury. Analysis of variance was performed to three groups, and showed a significant statistical difference（ F = 16.601, P 〈0.01）. Mann Whitney U test was performed to the articular cartilage of Ⅲ and Ⅳ grade, and showed a statistical difference（ Z = 2.24,P= 0.025 〈 0.05）. Using three dimensional MR reconstruction images of 1mm to measure cartilage lesion dimensions was more accurately than using two dimensional MR images. Friedman Test was performed （X^2 = 8.65, P = 0.013 〈 0.05）. Conclusion The percent error of the measurement on three dimensional reconstruction image is related to the MR scan thickness, the method of three dimensional reconstruction, the size of lesions and injury degree of lesions. Three dimensional MR reconstruction of cartilage can show cartilage surface irregularities. The direction of measurement is not limited by the MR scan plane, and the distance of any two points Can be measured.