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Hépatopathies chroniques : méthodes de quantification en IRM à 1,5 T et 3,0 T pour le diagnostic et le suivi

Abstract : Liver fibrosis is the main complication of chronic liver diseases, and cirrhosis, corresponding to the end-stage of fibrosis, is an important cause of morbi-mortality. The incidence increase of diabetes, metabolism disorders and obesity involve an increase of NAFLD which became the first cause of chronic liver disease in western countries. Since liver biopsy is the gold standard for the diagnosis of chronic liver diseases, inherent risks, intra- and inter-observer variability associated to an important cost motivate a clinical need to develop non-invasive methods for chronic liver disease assessment. Thus, the aim of this PhD thesis was to develop a method allowing the quantification of fat liver content and liver fibrosis using MRI at 1.5 and 3.0 T. For liver fibrosis quantification a method allowing liver perfusion parameters mapping using a MR dynamic contrast enhanced method was developed at 1.5 T. Then, in order to use a multi-parametric approach, a protocol allowing intra-voxel incoherent motion imaging (IVIM) was optimized at 3.0T. The aim was to combine liver perfusion imaging and IVIM. Regarding liver fat content quantification, a method including a correction of relaxation time effects using a disjointed estimation of T1 and T2* relaxation times of fat and water, accounting for the NMR spectrum of fat and resolving the dominant component ambiguity problem was developed. Liver perfusion parameters, in particularly portal perfusion and hepatic perfusion index were found relevant to make the distinction between no fibrosis, non-advanced fibrosis, advanced fibrosis and cirrhosis. About liver fat content quantification, fat volume fraction (FVF) given by our method allowed to quantify liver fat content accurately without cofounding factor-related bias. Moreover, FVF allowed diagnosing histological grade of steatosis with an excellent sensitivity/specificity. Combination of liver perfusion imaging and IVIM is actually under evaluation through the HEPATOMAP study using all the methodology developed through this PhD thesis. Preliminary results of this study have shown that the combination of information acquired with both the fat quantification and IVIM methods could allow distinction between NAFLD and NASH
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Benjamin Leporq. Hépatopathies chroniques : méthodes de quantification en IRM à 1,5 T et 3,0 T pour le diagnostic et le suivi. Imagerie médicale. Université Claude Bernard - Lyon I, 2012. Français. ⟨NNT : 2012LYO10279⟩. ⟨tel-02878784⟩

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