Goodwin D W, Wadghiri Y Z, Dunn J F
Department of Diagnostic Radiology, Dartmouth-Hitchcock Medical Center, Hanover, NH 03755, USA.
Acad Radiol. 1998 Nov;5(11):790-8. doi: 10.1016/s1076-6332(98)80264-x.
This study was designed to determine the relative influences of proton density versus collagen fiber orientation (through its influence on T2) in defining the layers of articular cartilage as seen in long-repetition-time magnetic resonance (MR) images. The authors mapped the T2 and proton densities of articular cartilage at 0 degree and 55 degrees with respect to the main magnetic field (B0) to determine the influence of T2 and water content on the normal laminar appearance of hyaline cartilage.
Six patellae of white-tailed deer were imaged at 7 T. T2 and proton densities were calculated from echo time versus signal intensity plots obtained with a multiecho, composite pulse sequence. Regions of interest in the radial and transitional zones were compared with the articular facets at 0 degree and 55 degrees relative to B0. Transmission electron microscopy was performed for correlation.
At 0 degree, T2 was longer in the transitional than in the radial zone (29 vs 11 msec). AT 55 degrees, T2 increased in both radial and transitional zones, although the difference between the zones decreased (37 vs 29 msec). There was no difference in proton density between the two layers.
Collagen fiber orientation, through T2 effects, is the dominant influence on the appearance of layers in hyaline cartilage in long-repetition-time MR images; proton density is not a major factor, and the collagen fiber orientation in the transitional zone is not totally random.
本研究旨在确定在长重复时间磁共振（MR）图像中，质子密度与胶原纤维取向（通过其对T2的影响）对关节软骨分层的相对影响。作者绘制了相对于主磁场（B0）在0度和55度时关节软骨的T2和质子密度图，以确定T2和水分含量对透明软骨正常分层外观的影响。
对6只白尾鹿的髌骨进行7T成像。T2和质子密度通过使用多回波复合脉冲序列获得的回波时间与信号强度图计算得出。将径向和过渡区的感兴趣区域与相对于B0在0度和55度的关节面进行比较。进行透射电子显微镜检查以进行相关性分析。
在0度时，过渡区的T2比径向区长（29对11毫秒）。在55度时，径向和过渡区的T2均增加，尽管两区之间的差异减小（37对29毫秒）。两层之间的质子密度没有差异。
通过T2效应，胶原纤维取向是长重复时间MR图像中透明软骨分层外观的主要影响因素；质子密度不是主要因素，并且过渡区的胶原纤维取向并非完全随机。
