2- Tissue and metabolic characterization

MRI: The non-alcoholic fatty liver diseases take a prominently large palace in liver damage with a wide spectrum of lesions extending from steatosis to fibrosis up to to cirrhosis and hepatocellular carcinoma with a significant risk of morbidity and mortality. Multiparametric analysis by combining the methods of perfusion, diffusion (intravoxel incoherent motion) and estimation of tissue viscoelastic properties (MR Elastography) associated in the same time to both imaging and proton spectroscopy (MRS) techniques for the quantification of fatty components provides the corresponding informations. This protocol, based on magnetic resonance, and performed within a single examination allows a non-invasive longitudinal monitoring for liver diagnosis.

MRS: Localized in vivo MRS provides metabolic information resource and offers the unique ability to non-invasively identify and measure intrinsic biomarkers. Primarily applied on the brain, the liver spectroscopy requires specific adaptation of the acquisition protocol. Our approach consists in using water suppressed spectrum to assess metabolic and lipid contents whatever the steatosis grade. Thanks to a home-made dedicated algorithm, quantitative profiles for liver spectroscopic data can be derived and compared with fat content measured by MRI. Knowing the chemical structure of a typical triglyceride molecule, it is possible by playing on the relative magnitude of each of the liver spectrum resonances to derive interesting insight about the lipid composition, e.g. saturated/unsaturated fatty acid proportion. This spectroscopic analysis is conducted both on human liver and for the study of steatosis mouse model. .

Intra-operative optical and fluorescence spectroscopy: Gliomas are the most frequent tumors of the central nervous system. They are infiltrative tumors with a solid tumoral component and an infiltrative component that is very difficult to identify. Their treatment is mainly based on resection as complete as possible. However the resection is limited because functional cerebral areas must be preserved to prevent postoperative definitive impairment. Indeed the infiltrative component is constituted of non-functional but also still functional areas. We demonstrated that intraoperative optical spectroscopy and protoporphyrin IX Fluorescence spectroscopy induced by aminolevulinic acid are relevant to identify the tumor tissues and particularly the infiltrative component [Biomed. Opt. Express 2013, http://www.creatis.insa-lyon.fr/site/fr/publications/43955]. During surgery, the decision to continue or stop resection is a tradeoff between the resection of a maximum of tumor cells and the preservation of functional areas. The aim of this project consists in the realization of an intraoperative multimodal optical system to assist the surgeon in this decision.