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Quantification in vivo de l’adiposité médullaire chez l’Homme par imagerie par résonance magnétique

Abstract : Bone marrow adiposity (BMA) is an underestimated tissue playing a key role in bonehomeostasis. To date, only magnetic resonance imaging (MRI) is able to exploreadequately and non-invasively this tissue in vivo. This work aims to clarify the mainbiases to take into account, to illustrate the value of BMA quantification to understandpathophysiological mechanisms, and finally, to promote its use for clinical purposes.The first axis of this work relies on a review of two fundamental methods to exploreBMA : proton magnetic resonance spectroscopy, and chemical shift encoding-basedwater-fat imaging. The use of these techniques is constrained by the differential magneticproperties of water and lipids, as well as the multiple interfaces between trabeculaeand bone marrow, fostering local magnetic inhomogeneities and reducingthe accuracy of BMA quantification. Clarifications on the major technical biases toconsider have been incorporated in a white paper written in collaboration with theMethodology Workgroup of the International Bone Marrow Adiposity Society.The second part of this work was based on the exploration of a paradoxical disease,anorexia nervosa, which affects multiple fat compartments. As a matter of fact, thedrastic depletion of peripheral adipose tissues contrasts with BMA expansion in anorexicpatients. Through a case-control study, the spectral characteristics of BMAat the hip of underweight (body mass index < 17.5 kg/m2) and weight-recoveredanorexic women have been compared to healthy volunteers. While no difference inthe spectral BMA profile was observed between anorexic patients, bone marrow fatfraction was significantly higher and the apparent lipid unsaturation levels lower inpatients compared to controls. Persistence of an abnormal BMA may take part in theincreased fracture risk in anorexic patients, even after weight recovery. This work hasbeen accepted for publication.Finally, although spectroscopic methods are the gold-standard for BMA quantification,its promotion in routine requires a simplification of its exploration. Chemicalshift encoding-based water-fat imaging appears to be a pertinent alternative approach.To illustrate its use for clinical purposes, a new case-control study, performed on postmenopausalwomen, has been initiated. Comparisons of BMA characteristics betweenwomen with a recent osteoporotic fracture and age-matched controls would providenew diagnostic elements for the evaluation of the fracture risk in postmenopausalosteoporosis. This is an on-going project, with preliminary results.The 3 axes of this research project highlight the clinical potential of BMA quantification.In the future, a multifactorial evaluation of bone, integrating data from themineral and organic compartments, would promote accurate expertise of bone healthand a better estimate of the fracture risk, especially in women with anorexia nervosaor postmenopausal osteoporosis.
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Submitted on : Friday, September 17, 2021 - 4:31:10 PM
Last modification on : Tuesday, November 22, 2022 - 2:26:15 PM
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  • HAL Id : tel-03347998, version 1



Sammy Badr. Quantification in vivo de l’adiposité médullaire chez l’Homme par imagerie par résonance magnétique. Médecine humaine et pathologie. Université de Lille, 2019. Français. ⟨NNT : 2019LILUS058⟩. ⟨tel-03347998⟩



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