PD ISO/TR 16379:2014 - Page 2

Tissue-engineered medical products. Evaluation of anisotropic structure of articular cartilage using DT (Diffusion Tensor)-MR Imaging. | Status: Current

1 Scope This Technical Report has been prepared for evaluation of therapeutic courses for articular cartilage disease and summarizes results from structural evaluation of knee joint cartilage by diffusion tensor imaging, an MRI applied technology allowing non-invasive observation of soft tissue morphology in vivo. This Technical Report is intended for use in areas such as regenerative medicine for knee joint cartilage disease. After in vivo transplant of cartilage cells or tissue as a regenerative treatment, longitudinal diagnosis is needed to assess regeneration as articular cartilage, but arthroscopes used primarily for this purpose are invasive and also do not allow evaluation of structure by simple observation of surfacial characteristics. Radiography and CT do not visualize articular cartilage and also entail the problem of exposure. Collagen fibres, the primary component of articular cartilage, have a surfacial layer parallel to the articular surface to serve a lubricating function for the articular surface, a middle layer with a randomized structure to distribute loads, and deep layers oriented vertically to support loads. The anisotropy of this three-layer structure is a characteristic feature of hyaline cartilage structures and a mechanism demonstrating a lubricating function for articular cartilage. We can then ask whether articular cartilage can be assessed by evaluating the anisotropy of collagen. MRI techniques allow non-invasive visualization of soft tissue form and function in vivo, and DT-MRI conveys the direction of water molecule motion. In fibrous tissues, the direction of water molecule motion is restricted to the direction of fibre orientation; consequently, the direction of water molecule motion matches that of fibre orientation. The use of DT-MRI therefore does allow evaluation of collagen fibre orientation and anisotropy in articular cartilage. DT-MRI is thus used to observe articular cartilage anisotropy data for use as standardized data in longitudinal diagnosis following transplant of articular cartilage as a regenerative treatment.