Date : 17/03/2011

Laboratory
IR4M UMR8081
CNRS Université Paris Sud
Bat 220
91405 Orsay
Website : http://ir4m/www.u-psud.fr
Main discipline : Physics
Lab director : Luc Darrasse

PhD Supervisor
Geneviève Guillot
email : This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
phone : +33.1 69 15 67 46

Subjects
1.: cortical bone
2.: trabecular bone
3.: mechanical properties

Tools and methodologies
1.: Magnetic Resonance Imaging
2.: x ray high resolution tomography
3.: digital image correlation

Summary of lab's interests

IR4M (Imagerie par Résonance Magnétique et Multi-Modalités, UMR8081 Univ Paris-Sud CNRS, headed by Luc DARRASSE) gathers five research teams with recognized expertise in different modalities of medical imaging, mostly MRI and ultrasound. IR4M is maintaining and developing a platform of different MR scanners dedicated to research, including a small animal scanner assembled in the laboratory around a 4.7 T horizontal magnet, with a powerful gradient system (400 mT/m within 100 µs), and on which the UTE sequence has been implemented and can be used with a high spatial resolution (0.1 mm) on small samples. Geneviève Guillot (head of the IR4M team involved in this project) has a recognized expertise on sequence development and application of MRI to bone, cartilage, and lung imaging.

Summary of project

The PhD project aims at applying new quantitative imaging methods of the bone tissue, to assess their efficiency in predicting its mechanical behavior, concerning trabecular bone as well as cortical bone, and going as far as possible down to the local scale. UTE-MRI will be used for cortical bone porosity assessment, and this measurement will be compared to reference BMD measurements by DEXA and by X-ray tomography. A series of human bone samples (femur) is available at B2OA, for which the mechanical properties have been measured at the scale of the whole bone. High resolution 3D images will be acquired ex vivo by X-ray tomography under different load conditions, from which the 3D displacement field can be deduced by image correlation. This technique is well suited to trabecular bone, which corresponds to images with a large spatial distribution of gray-levels. The feasibility to adapt this technique will be explored for anatomical samples (ex: femur) for which the bone m atrix is either mainly cortical (diaphysis) or mostly trabecular (femoral head), trying to precise the technical limitations (accessible FOV, sensitivity range and necessary resolution).

Interdisciplinarity of the project

The PhD project is run between three CNRS laboratories in Paris area, IR4M UMR8081 (Univ Paris Sud), B2OA UMR7052 (Univ Paris 7, Valérie BOUSSON), and LMT UMR8535 (ENS Cachan Stéphane ROUX), which gather the necessary equipment and different expertise. The different teams (UMR8081, UMR7052, UMR8535) gather different complementary expertise for the project: the development of new MRI methods (UMR8081); the assessment of 2D and 3D BMD measurement at different scales by X-ray absorption and X-ray tomography (UMR7052); software development for computing the 3D displacement field by digital image correlation (UMR8535).