Wachsmuth Lydia, Keiffer Rolf, Juretschke Hans-Paul, Raiss Ruth X, Kimmig Nicole, Lindhorst Elmar
Institute of Medical Physics, University Erlangen-Nuernberg, Erlangen, Germany.
Osteoarthritis Cartilage. 2003 Dec;11(12):891-902. doi: 10.1016/j.joca.2003.08.008.
In this longitudinal MR study the early stages of joint pathology in two surgically-induced rabbit models of osteoarthritis (OA) were monitored by in vivo contrast-enhanced MRI at 7.1T. Qualitative and quantitative MR data were compared with macroscopic and microscopic findings.
Scanning of mature, male New Zealand White rabbits (N=12) was performed before surgery, and at 2, 4, and 8 weeks after unilateral transection of the anterior cruciate ligament (ACLT), medial meniscectomy (ME), or sham operation. MR-images were simultaneously obtained of both knee joints after intravenous injection of Magnevist. We implemented a 2D T1-weighted (T1w) coronal, fat-saturated gradientecho protocol (68 x 138 microm2, slice thickness 1 mm). Additionally, consecutive 3D gradientecho images were obtained from two sham-operated and two rabbits of the ME group (234 x 273 x 234 microm(3)). ACLT animals were sacrificed at 2 weeks (N=1), and 8 weeks (N=3), ME animals were sacrificed at 4 weeks (N=2), and 8 weeks (N=4), and sham-operated animals were sacrificed at 2 weeks (N=1) and 8 weeks (N=1), respectively.
Both OA models reflected important characteristics of the clinical picture of OA. With MR we were able to monitor time dependently the decline of synovial effusion and the formation of osteophytes. Morphologic MR examination showed a moderate to high accuracy for detecting synovial effusion (75%), meniscus (86%) and cruciate ligament (91%) lesions, and osteophytes (88%) as assessed by macroscopic examination. False-negative MR findings for gross macroscopic changes were due to the relative high slice thickness in 2D scans and the fact that the slices only covered the main weightbearing area of the femorotibial joint. Contour abnormalities of articular cartilage were not reliably detected. Quantitative analysis revealed a statistically significant increase of cartilage signal intensity in medial tibial cartilage (48+/-9% ACLT, and 29+/-9% ME in 2D datasets) as compared to contralateral control knees in two-week scans. Signal enhancement persisted or increased at later dates.
With high-resolution contrast-enhanced MRI at 7.1T the time course of gross pathologic changes in rabbit knees with surgically induced OA can be monitored. Still insufficient spatial resolution and image contrast of the applied 2D protocols limit the sensitivity and prohibit detection of articular cartilage contour abnormalities. However, signal alterations in the cartilage layer indicate alterations of tissue composition at a very early stage of OA development. When used with 3D protocols, contrast-enhanced MRI offers a promising tool for qualitative and quantitative in vivo monitoring of OA in rabbit models.
在这项纵向磁共振研究中，通过7.1T的体内对比增强磁共振成像监测两种手术诱导的兔骨关节炎（OA）模型中关节病理的早期阶段。将定性和定量的磁共振数据与宏观和微观发现进行比较。
对成熟的雄性新西兰白兔（N = 12）在手术前、单侧前交叉韧带横断术（ACLT）、内侧半月板切除术（ME）或假手术后2、4和8周进行扫描。静脉注射马根维显后同时获取两个膝关节的磁共振图像。我们实施了二维T1加权（T1w）冠状位脂肪饱和梯度回波协议（68×138平方毫米，层厚1毫米）。此外，从两只假手术和两只ME组的兔子中获取连续的三维梯度回波图像（234×273×234立方毫米）。ACLT组动物在2周（N = 1）和8周（N = 3）处牺牲，ME组动物在4周（N = 2）和8周（N = 4）处牺牲，假手术动物分别在2周（N = 1）和8周（N = 1）处牺牲。
两种OA模型均反映了OA临床表现的重要特征。通过磁共振成像，我们能够随时间监测滑膜积液的减少和骨赘的形成。形态学磁共振检查显示，在检测滑膜积液（75%）、半月板（86%）和交叉韧带（91%）损伤以及骨赘（88%）方面具有中度至高准确性，这些均通过宏观检查评估。磁共振成像对于宏观大体变化的假阴性结果是由于二维扫描中层厚相对较高，以及切片仅覆盖了股骨胫关节的主要负重区域。关节软骨轮廓异常未被可靠检测到。定量分析显示，与对侧对照膝关节相比，在两周扫描中内侧胫骨软骨的软骨信号强度有统计学显著增加（二维数据集中ACLT组为48±9%，ME组为29±9%）。信号增强在后期持续或增加。
使用7.1T高分辨率对比增强磁共振成像可以监测手术诱导的兔膝关节OA大体病理变化的时间进程。所应用的二维协议的空间分辨率和图像对比度仍然不足，限制了敏感性并阻碍了关节软骨轮廓异常的检测。然而，软骨层中的信号改变表明在OA发展的非常早期阶段组织成分发生了改变。当与三维协议一起使用时，对比增强磁共振成像为兔模型中OA的体内定性和定量监测提供了一个有前景的工具。
