家猪体外胰蛋白酶消化关节软骨的7.0T磁共振T2弛豫时间图与量化分析

Regional changes of T2 relaxation on porcine patellar cartilages in vitro by means of degradation enzymatically at 7.0T MR

目的应用超高场7.0T磁共振T2加权成像技术、弛豫时间图和量化分析的方法评价体外胰蛋白酶消化与未消化家猪髌骨软骨T2弛豫时间的改变。方法选择10头家猪,各取左、右侧髌骨。左侧髌骨10个为实验组,右侧髌骨10个为对照组,分别浸泡于含有胰蛋白酶的PBS溶液及PBS中,4h后取出。利用7.0T磁共振机,分别采用多回波SE序列进行扫描,获得离体家猪髌骨关节软骨的T2加权图像。用自行编制的软件重构T2弛豫时间图,人工标注感兴趣区,分层定量测定关节软骨的T2值。结果经酶诱导消化的离体家猪髌骨关节软骨T2W成像清晰,呈分层状表现,对比度好,无异常伪影。对照组与实验组关节软骨T2WI关节软骨未见局部信号异常改变。与对照组比较,实验组软骨全层、表层、中间层T2值差异有统计学意义(P<0.05),而两者的深层与钙化层差异无统计学意义(P>0.05)。结论经胰蛋白酶诱导消化可引起退变软骨T2弛豫时间改变,在软骨的表层及中间层变化明显,提示T2弛豫时间是较敏感、特异的检测指标,可进一步应用于关节软骨退变的早期诊断。

Objective To investigate signal changes in transverse relaxation （T2） from porcine articular cartilages after the trypsin digestion in vitro. Methods T2 relaxation times were measured from porcine patellar cartilages. The samples （n= 20） were assigned to 2 groups. Group A of right patellar samples （n= 10） were immersed in PBS and served as self-control group. The left patellar samples （n=10） were immersed in PBS with trypsin for 4 h and served as treated group （B）. T2-images were collected with a spin-echo sequence on a 7.0T scanner. Using a home-built analysis program, T2-maps were obtained and the cartilage from each sample was manually segmented by drawing regions-of-interest. This segmentation separa ted the patellar cartilage into four layers （superficial, middle, deep and calcified）, which represented the superficial, transitional, radial, calcified zones respectively, to investigate regional differences of T2 in patellar cartilage. Results T2 relaxation in full, superficial and middle layers （P〈0.05） increased significantly in samples after 4 h trypsin digestion, whereas T2 relaxation showed no difference on both deep and calcified layers when compared to the control group. Conclusion T2 relaxation changes at the articular cartilage with a hyperintense lamina are sensitive to typsin digestion, which might correlate to PG loss and increased water content. Thus, T2 measurements can be used as non invasive evaluation method for on-set cartilage disease.