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Micro-imagerie RMN du cartilage

Abstract : MR imaging has been shown to directly visualize the cartilage contrary to other imaging approaches but reports were as far conflicting regarding the real significance of imaging patterns depicted in MRI. Using an experimental osteoarthritic model on rat, we demonstrated that proton SE images were well adapted to depict morphological modifications of cartilage as well as variations of its internal structure (laminar appearance).We showed on a clinical scanner (1.5Tesla) that T1-weighted sequences were accurate to delimit the bovine cartilage boundaries and to determine its thickness. However, these sequences could not permit to characterize the cartilage structure itself depicted as homogeneous. Conversely, with T2-weighted sequences, MR pattern of cartilage was heterogeneous and our data, supported by correlations with histology and biochemistry, showed that this heterogeneity was not artefactual but was supported by variations inside the cartilage structure. In order to confinn the potentiality of the T2 weighted sequences raised by results obtained on bovine samples, we developed on rat patellar cartilage, and using a 8.5 Tesla micro imager, a T2 mapping technique. We observed on one hand a decrease of global T2 values during the maturation and aging processes and on the other hand, zonal variations of T2 values with cartilage depth. We demonstrated that these variations reflect the evolution of the cartilage matrix content and particularly the collagen content but also its organization. With a proteoglycans depletion model (hyaluronidase digestion), we noted that proteoglycans depletion leads to an increase of T2 values, this increase being proportional to the loss in proteoglycans. Such phenomenon might be explained byan influx of proton molecules in the free space provoked by the proteoglycan loss. T2 mapping looks as a very promising technique that should permit to define more precisely the different steps of matrix cartilage lesions and thus to increase our knowledge regarding the early stages of OA disease. In a therapeutic perspective, T2 mapping would pennit to evaluate quantitatively the effectiveness - and the tolerance - of drugs on cartilage, even before any morphological chondrallesion could be depicted.
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Submitted on : Thursday, March 29, 2018 - 10:46:45 AM
Last modification on : Friday, June 25, 2021 - 12:08:37 PM

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  • HAL Id : tel-01746876, version 1


Damien Loeuille. Micro-imagerie RMN du cartilage. Médecine humaine et pathologie. Université Henri Poincaré - Nancy 1, 2002. Français. ⟨NNT : 2002NAN10303⟩. ⟨tel-01746876⟩



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