Photoacoustic (PA) signals are known to be wideband thanks to their N-shape. Yet ultrasound (US) transducers commonly used for PA imaging use piezoelectric technology (PZT) and hence present a limited bandwidth in reception. Thus, PA signals can not be fully acquired and are filtered by the receiver. Capacitive micromachined ultrasonic transducer (cMUT) technology has emerged as an alternative to conventional PZT transducers in the field of medical imaging. Among the interesting properties offered by this technology, a theoretically infinite bandwidth in reception may be reached. In this work the interest of cMUT larger bandwidth for PA imaging is studied by comparing a cMUT and a classical PZT linear US probes. PA acquisitions have been made on several homemade bimodal phantoms whose properties are well-known. For each phantom, acquisitions have been realized with both probes in the same conditions. The probes characteristics have been verified for the reception of PA signals and three criteria have been evaluated to compare the two probes: signal-to-noise ratio (SNR), contrast-tonoise ratio (CNR), and the maximal amplitude of PA signals. The cMUT probe presents indeed a larger fractional bandwidth in reception and the SNR and CNR are enhanced by at least 6dB. Furthermore, the sensitivity of the cMUT probe is higher and it receives 4 to 5 times more signal than the PZT probe. Therefore, this work highlights the potential of cMUT technology for PA imaging through quantitative as well as qualitative parameters.

International audienceIntegrating the ultrasounic pulse-echo (PE) and optoacousic (OA) imaging is a potent approach in rendering the volumetric images of biological tissues. The deliverable information are essentially uncorrelated but highly complementary in learning about the optical and mechanical properties of the medium. Yet, owing to the inhomogeneities in acoustic velocity and the optical scattering, this synergistic approach suffers from the low depth resolution, low contrast and artifacts like off-axis contributions and phase distortion. In this work, an adaptive weighted dynamic focusing based reconstruction technique namely, weighted synthetic aperture (WSA), has been developed to address the aforementioned defects, in particular for annular array. Our findings show the efficiency of WSA method in 3D reconstruction of simulated phantom. We elaborate WSA to estimate the spatial location, size, reflectivity function and absorption coefficient of the insonified/illuminated targets for both imaging modalities. The phase distortion introduced by the separable delay approximation is addressed with an adaptive weighting factor that combines coherence factor (CF) and phase coherence factor (PCF). In addition, the weighting factor incorporates the spatial impulse response (SIR), which is associated with the properties of the transducer in order to inverse the effect of the transducer on imaging quality. Using numerical phantom, the simulation results demonstrate thatincorporating SIR into the weighting factor ensures the isotropic sensitivity while CF and PCF are suppressing the artifacts, grating lobe and phase aberration for both OA and PE images

Progressive multiple sclerosis (MS) is driven by demyelination, neuroaxonal loss, and mitochondrial damage occurring behind a closed blood-brain barrier (BBB). Patients with progressive MS typically fail to respond to available immunomodulatory drugs that reduce relapses in early disease. This indicates a dire need to identify non-canonical therapeutic avenues to limit neurodegeneration and promote protection and repair. Here, we have employed high-resolution multiomic profiling to characterise the biochemical and metabolic adaptations underpinning MS pathology, as these have been incompletely described but critically, may be amenable to BBB-permeable drug targeting. Using synchrotron radiation (SR)- and focal plane array (FPA)-based Fourier transform infrared microspectroscopy (μFTIR), we spatially mapped the biochemical features present in human progressive MS and control post-mortem brain and rare spinal cord tissue. By employing single-nuclear RNA sequencing (snRNA-seq), 10x Genomics Visium spatial transcriptomics and spatial proteomics to resolve their cellular context, we found that these biochemical features provide a uniquely and highly disease-specific barcode for distinct pathological niches within the tissue. Characterisation of the metabolic processes underpinning these niches revealed an associated re-organisation of the astrocytic landscape in the grey and white matter, with implications for the treatment of progressive MS.

Focal plane array (FPA) detectors have escalated Fourier transform infrared (FTIR) microspectroscopy to a potent hyperspectral imaging method. Yet, despite the instrumental multiplex/multichannel advantages, the fidelity of the hyperspectral images relies on the throughput as the total flux of the source is divided among each FPA pixel. Additionally, maintaining the spectral resolution requires a certain level of collimation of the beam which adversely affect the flux of high étendue source. To this end, we propose an implementation of two deformable mirror (DM) sensorless adaptive optics system for infrared (IR) source coupling. The deflection shape of each DM membrane is optimized individually to deal with the beam intensity and the rays’ direction in a separate manner, while preserving the spectral quality across the entire mid-IR range. This paper contemplates the choice of metrics in sequential optimization in conjunction with two variations of stochastic parallel gradient descent optimization algorithm. We discuss this approach with respect to a state-of-the-art FTIR microscope.

Optoacoustic ultrasound (OPUS) is a promising hybridized technique for simultaneous acquisition of functional and morphological data. The optical specificity of optoacoustic leverages the diagnostic aptitude of ultrasonography beyond anatomy. However, this integration has been rarely practiced for volumetric imaging. The challenge lies in the effective imaging probes that preserve the functionality of both modalities. The potentials of a sparse annular array for volumetric OPUS imaging are theoretically investigated. In order to evaluate and optimize the performance characteristics of the probe, series of analysis in the framework of system model matrix was carried out. The two criteria of voxel crosstalk and eigenanalysis have been employed to unveil information about the spatial sensitivity, aliasing, and number of definable spatial frequency components. Based on these benchmarks, the optimal parameters for volumetric handheld probe are determined. In particular, the number, size, and the arrangement of the elements and overall aperture dimension were investigated. The result of the numerical simulation suggests that the segmented-annular array of 128 negatively focused elements with 1λ  ×  20λ size, operating at 5-MHz central frequency showcases a good agreement with the physical requirement of both imaging systems. We hypothesize that these features enable a high-throughput volumetric passive/active ultrasonic imaging system with great potential for clinical applications.