MULTIPARAMETRIC MRI OF CARTILAGE

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Non-destructive techniques for accurately assessing the structural and functional integrity of cartilage are essential for defining the natural history of arthritis and for evaluating the effects of prevention and therapeutic interventions. Our long term goal is to establish magnetic resonance imaging (MRI) techniques for evaluating the compositi0nal and functional integrity of articular cartilage. In the first cycle of this award, we used MR spectroscopy studies to demonstrate and characterize the sensitivity of several MR measurable parameters designed to measure important cartilage properties. We demonstrated that diffusivity of water was sensitive to cartilage structure; magnetization transfer (MT) was sensitive to collagen content and structure, and sodium concentrat6ion could be used to quantify GAG concentration. Furthermore, comparative studies of interleukin-1 and trypsin degradation revealed the power of a multiparametric approach over individual measurements We then focused on applying MR in an imaging mode. Given the difficulties in imaging sodium by MR, we first focused on developing a proton based MR method for measuring GAG concentration. The resulting technique was extensively validated. High resolution images of spatial and temporal variations in cartilage GAG technique was extensively validated. High resolution images of spatial and temporal variations in cartilage GAG highlighted the increased information available when the spatial distribution of tissue constituents can be obtained. Finally, the in vivo (clinical) feasibility and validity of this technique to detect variations in GAG in human cartilage was demonstrated. The overall aim of this next cycle is to explore the other MR parameters in an imaging mode and combine them for a multiparametric MRI study. The specific aims of this proposal are: (1) To compare the spatial and temporal distribution of the set of MRI parameters during induced degradation and regeneration of bovine cartilage in culture. (2) To apply the multi multiparametric MRI approach to human tissue in different stages of natural disease. (3) To use the developed MR measures to identify areas of human cartilage with and without identified collagen and/or GAG abnormalities, and monitor these samples in culture. (4) To develop and apply the multiparametric MRI approach to tissue engineered cartilage constructs. The long term results of these studies should therefore yield the unprecedented opportunity to non-destructively monitor the spatial distribution and temporal evolution of critical cartilage constituents in living tissue at near-histologic resolution in isolated cartilage and at clinically relevant resolutions in vivo, studies which were previously not feasible.