! STAGE POURVU !
Type de stage
Stage de Master 2 / stage de fin d’étude d’école d’ingénieur
Date ou durée du stage
2021
Contexte
Blood flow in bone plays a key role in bone metabolism, growth and maintenance (remodeling, fracture healing, implant osseointegration). It is also related to the development of bone metastasis. Unfortunately, there is at present no suitable technique for the in vivo assessment of bone vascularization. Ultrasound (Doppler techniques) is the modality of choice for blood flow assessment in vivo in soft tissues but it could not be applied to bone until recently because of high ultrasound attenuation and refraction.
The laboratory LIB is developing original ultrasound imaging and Doppler sequences, together with dedicated reconstruction algorithms to assess blood flow within cortical bone tissue. The first results obtained recently have demonstrated that signals representing blood flow in the direction of bone axis and perpendicular to bone axis can be measured (Salles et al. 2020). The interpretation of this signal remains a challenge as little is known about bone vascularization. In particular, there is a lack of reference data on the direction of flows and on their velocities.
Cortical bone is a dense mineralized tissue pervaded by pores oriented along and transverse to the long bone axis (pore volume fraction around 10%). The pore network is well documented with high resolution X-ray computed tomography: these 3D images provide a detailed description of the cavities in which the vessels run (arteries, veins and capillaries). Our hypothesis is that information on blood flow in bone can be inferred from the properties of the pore network. For instance, the direction of the pores and their diameter should be related to the macroscopic direction and intensity of flow.
Objectif
The project is at the crossroads of several research fields: bone physiology, image processing and ultrasound functional imaging. The objective of the project is to design a model of ultrasound backscattered signal from blood mircocirculation in cortical bone.
Mission(s)
A few typical bone microstructures will be selected in a collection of high-resolution 3D images. The images will be processed to obtain the trajectories of the pores and their diameter. These trajectories will then be used to model the intra-osseous vascular network relying on literature data to position veins, arteries and capillaries. Several scenari of vascular models and flows will be considered. For each model, the effective ultrasound backscattered signals will be generated resorting to available simulation tools (e.g., Field II). Finally, these signals will be used to simulate the effective Doppler signals which will be compared to in vivo Doppler signals.
Compétences
The successful candidate is expected to have a strong interest in biomedical research and good programming skill. He/she should have a background in physics, engineering or signal processing and have at least basic knowledge in acoustics (ultrasound) or image processing.
Rémunération
Gratifications de stage
Contact
Send CV and cover letter to quentin.grimal[at]sorbonne.universite.fr
Host laboratory:
Supervisors : Quentin GRIMAL, Sébastien SALLES
Affiliation: Sorbonne Université
Laboratoire d’Imagerie Biomédicale (LIB) CNRS 7371 – INSERM 1146
Address : 15, rue de l’Ecole de Médecine 75006 Paris
Collaborations:
Guillaume RENAUD, Department of Imaging Physics, Delft University of Technology, The Netherlands
Françoise PEYRIN, CREATIS, CNRS 5220, INSERM U1206, Lyon