title: In vivo structural analysis of articular cartilage using diffusion tensor magnetic resonance imaging.
abstract: OBJECTIVE
  The articular cartilage is a small tissue with a matrix structure of three layers between which the orientation of collagen fiber differs. A diffusion-weighted twice-refocused spin-echo echo-planar imaging (SE-EPI) sequence was optimized for the articular cartilage, and the structure of the three layers of human articular cartilage was imaged in vivo from diffusion tensor images.
  
  
  METHODS
  The subjects imaged were five specimens of swine femur head after removal of the flesh around the knee joint, five specimens of swine articular cartilage with flesh present and the knee cartilage of five adult male volunteers. Based on diffusion-weighted images in six directions, the mean diffusivity (MD) and the fractional anisotropy (FA) values were calculated.
  
  
  RESULTS
  Diffusion tensor images of the articular cartilage were obtained by sequence optimization. The MD and FA value of the specimens (each of five examples) under different conditions were estimated. Although the articular cartilage is a small tissue, the matrix structure of each layer in the articular cartilage was obtained by SE-EPI sequence with GRAPPA. The MD and FA values of swine articular cartilage are different between the synovial fluid and saline. In human articular cartilage, the load of the body weight on the knee had an effect on the FA value of the surface layer of the articular cartilage.
  
  
  CONCLUSIONS
  This method can be used to create images of the articular cartilage structure, not only in vitro but also in vivo. Therefore, it is suggested that this method should support the elucidation of the in vivo structure and function of the knee joint and might be applied to clinical practice.
authors: Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan. azuma@frontier.kyoto-u.ac.jp
authors: Takashi
authors: T
authors: Azuma
authors: Ryusuke
authors: R
authors: Nakai
authors: Osamu
authors: O
authors: Takizawa
authors: Sadami
authors: S
authors: Tsutsumi
mesh_terms: D000465:Algorithms; D000818:Animals; D016880:Anisotropy; D002358:Cartilage, Articular / Q000473:pathology*; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D006801:Humans; D007719:Knee Joint / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011108:Polymers / Q000737:chemistry; D013552:Swine; D013582:Synovial Fluid / Q000378:metabolism
chemical_list: D011108:Polymers