François Varray

Associate Professor.

I developed a strong expertise in instrumentation and sequence design to provide ultrafast imaging with either 2D or 3D systems [Applied Sciences 2018]. Such advanced acquisitions and associated post-processing allow them to product high-quality images and advanced post-processing strategies such as optimised beamforming [IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2021], optimal 3D sparse array design [Scientific reports 2018], 3D motion compensation for Doppler imaging [IEEE Open Journal of Ultrasonics, Ferroelectrics, and Frequency Control 2023] or 3D transverse oscillations [IEEE International Ultrasonics Symposium 2019].

Recently, I tried to image the micro-orgnisation of the heart muscle in ultrasound imaging with the framework of LabEx PRIMES. Indeed, I previously developed a strategy in synchrotron radiation phase-contrast micro-tomography (SR-PCT) at an isotropic 3.5 µm resolution [MedIA 2017]. In ultrasound, the acquisition pipeline and post-processing are different and based on the local coherence of the raw ultrasound signals [IEEE International Ultrasonics Symposium 2019]. To this end, we extend the initial strategy to evaluate the full 3D local angle of the fibre [IEEE International Ultrasonics Symposium 2019]. The final objective is to compare such measures to diffusion magnetic resonance imaging.

In collaboration with the LabTau and within the framework of LabEx CeLyA, we developed advanced beamforming strategies to image the cavitation map produced during treatment. The beamforming strategies are based on adaptive measurement as phase coherence factor [IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2018] or robust CSM estimation for advanced array processing beamforming (robust capon, Pisarenko class beamformer or MUSIC) in the Fourier domain [IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2020]. Currently, such developments are extended in 3D.

Since my recruitment in 2013, I have been developing activities in photoacoustic imaging either in system development [Photoacoustics 2017], array design [Optical Express 2020] or post-processing algorithms for multispectral imaging [EURASIP Journal on Advances in Signal 2018, Sensors 2021]. Then, based on this expertise, applications on photothermal complexes have been evaluated for bioimaging [Langmuir 2019]. Lately, I have been involved in the International Photoacoustic Standardisation Consortium to formalize the photoacoustic data format and to propose advanced beamforming strategies and their comparison [Photoacoustics 2022].