Modifications of orientational dependence of microscopic magnetic resonance imaging T 2 anisotropy in compressed articular cartilage

Purpose To investigate the compression‐induced changes in the orientational characteristics in T 2 anisotropy of articular cartilage using microscopic magnetic resonance imaging (μMRI). Materials and Methods Six beagle specimens were subjected to various levels of strain (0% to 27%) and were imaged at a minimum of two orientations (0° and 55°). Two specimens at 14% and 27% strain were imaged at every 5° increment over the first quadrant of the angular space. Quantitative two‐dimensional T 2 images and three‐dimensional T 2 anisotropy maps of cartilage were constructed at a 19.8‐μm in‐depth resolution. Results The load‐induced laminar appearance of cartilage at the magic angle became more distinct as the strain level increased. T 2 anisotropy maps of cartilage at 14% and 27% strain exhibited load‐induced modifications in the collagen fibril ultrastructure, with a new peak toward the cartilage‐bone interface and alterations to orientational dependence of T 2 anisotropy. Conclusion Distinct alternations in the orientational dependence of μMRI T 2 anisotropy reflect the organizational modification of the collagen matrix due to external loading. This approach could become useful in detecting changes in cartilage's macromolecular structure due to injury or diseases. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.