Quantification de la stéatose hépatique par la séquence triple-écho (principes, validation et imagerie paramétrique)

DIJON-BU Médecine Pharmacie (212312103) / SudocSudocFranceF

Evalution de la séquence IRM triple échos pour la mesure de la charge en fer hépatique avec mesure conjointe de la stéatose à 1,5 tesla

DIJON-BU Médecine Pharmacie (212312103) / SudocSudocFranceF

Intérêt de l'IRM das le suivi des cirrhoses indemnes de carcinome hépatocellulaire ((210 patients))

DIJON-BU Médecine Pharmacie (212312103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Detection and localization of acute lower gastrointestinal bleeding prior to therapeutic endovascular embolization: a challenge!

International audienc

[Fast technique to quantify liver steatosis at 3T: principles, parametric imaging and applications]

International audienceThe purpose of this article is to present a fast and clinically usable technique for quantification of liver steatosis. This technique, based on a triple-echo gradient-echo sequence (in-phase, opposed-phase, in-phase), has recently been validated with excellent correlation and accuracy compared to proton MR spectroscopy. The theoretical principles are reviewed, with emphasis on the need to correct for the T2* decay inherent to the use of in-phase and opposed-phase sequences. T1 decay also is negligible due to the use of a low flip angle (20 degrees). The advantage of this technique is that it can generate a parametric representation (map) of liver steatosis, after fast and simple post-processing, based on measurements from standard images (addition, subtraction, division, multiplication) available on the MR scanning console. This parametric method allows quantification of steatosis in focal lesions. The main limitation of the technique relates to its ambiguity with lipid content over 50%, a phenomenon that does not occur with liver steatosis

Evidence of Tri-Exponential Decay for Liver Intravoxel Incoherent Motion MRI: A Review of Published Results and Limitations

International audienceDiffusion weighted imaging (DWI) and intravoxel incoherent motion (IVIM) have been explored to assess liver tumors and diffused liver diseases. IVIM reflects the microscopic translational motions that occur in voxels in magnetic resonance (MR) DWI. In biologic tissues, molecular diffusion of water and microcirculation of blood in the capillary network can be assessed using IVIM DWI. The most commonly applied model to describe the DWI signal is a bi-exponential model, with a slow compartment of diffusion linked to pure molecular diffusion (represented by the coefficient Dslow), and a fast compartment of diffusion, related to microperfusion (represented by the coefficient Dfast). However, high variance in Dfast estimates has been consistently shown in literature for liver IVIM, restricting its application in clinical practice. This variation could be explained by the presence of another very fast compartment of diffusion in the liver. Therefore, a tri-exponential model would be more suitable to describe the DWI signal. This article reviews the published evidence of the existence of this additional very fast diffusion compartment and discusses the performance and limitations of the tri-exponential model for liver IVIM in current clinical settings