1- Hybrid imaging: MR-optics, MRI-US, US-optics coupling

Bimodal optics/MR endoluminal probe:

Imaging and spectroscopic advantages of NMR and optics are combined to improve non-invasive early detection and diagnosis of lesions in the gastro-intestinal tract. The development of endoluminal radiofrequency (RF) coils removes the obstacles inherent to the investigation of deep organs. The high spatial resolution achievable with endoluminal coil provides detailed information on the local anatomy and pathology. Optoelectronic components have to be used to address safety issues using MR endoluminal RF probes. Our approach is to combine optical spectroscopy in the form of autofluorescence and reflectance spectroscopy with High spatial Resolution Magnetic Resonance Imaging (HR-MRI) within an endoluminal bimodal probe to provide a tool capable of extracting both biochemical data and morphological data simultaneously.  

Bimodal Optics/MR imaging of cerebral activity:

Neuro-vascular coupling is still an open problem whereas several major imaging techniques are based on it. Optical contrast has a strong hemodynamic contribution (like BOLD fMRI) and also a contribution that is more closely related to neuronal activation (EROS). Then it is a promising tool to explore these mechanisms. Bi-modalities MR/Optics is relevant here because of the complementarities of optical and MR contrasts. We showed that in songbirds a new time-resolved and wavelength-resolved technique is relevant for the exploration of brain activity [J. Cereb. Blood Flow & Met. 2011,  http://www.creatis.insa-lyon.fr/site/fr/publications/MOTT-11a]. A major concern is to measure and isolate the different contributions in the intrinsic optical signal. We aim at developing a bimodal system (time-resolved and wavelength-resolved optical instrumentation) and compatible with MR environment so as to measure simultaneously MR contrasts. A longer term goal is to go towards a real Diffuse Optical Tomography of cerebral activity.

 

MR/US Elastography:

               A new elastographic method that combines the information from quasi-static ultrasound (US) and magnetic resonance (MR) elastography is proposed to improve diagnosis of diseases characterized by modifications in tissue stiffness. Current works on that field only provide a comparison of stiffness measurements obtained with MR and transient US elastography for gels mimicking soft tissues. The new method will first require improvements of both techniques (e.g. 3D quasi-static US elastography instead of current 2D, to overcome plane misalignment issues) prior to combination. It is expected that the new technique will improve diagnosis, in particular for breast cancer detection and liver fibrosis assessment. MR elastography is also developed with a perspective to be applied to small animal models. As a result, specific instrumental setup and high frequency elastography is being developed.

 

US/optics: Photoacoustic

PhotoAcoustic Tomography (PAT) combines the advantages of high optical absorption contrast in biological tissues and optical spectroscopy with excellent spatial resolution of ultrasound imaging techniques. The optical absorption of short laser pulses from different tissue structures produces localized heating and thermal expansion, which generates thermoelastic stress waves (ultrasonic waves) identified as photoacoustic (PA) signals. PAT has demonstrated unprecedented quality in imaging vascular structures deep in small animals and has clearly shown enormous potential in clinical applications due to its non-invasive nature. We particularly focus on the development Quantitative PAT, based on more realistic photoacoustic models that take into account the very inhomogeneous tissues optical properties.