PERFORMANCE OF BLIND DECONVOLUTION IN OPTOACOUSTIC TOMOGRAPHY

In this paper,we consider the use of blind deconvolution for optoacoustic(photoacoustic)imaging and investigate the performance of the method as means for increasing the resolution of the reconstructed image beyond the physical restrictions of the system.The method is demonstrated with optoacoustic measurement obtained from six-day-old mice,imaged in the near-infrared using a broadband hydrophone in a circular scanning configuration.Wefind that estimates of the unknown point spread function,achieved by blind deconvolution,improve the resolution and contrast in the images and show promise for enhancing optoacoustic images.

Functional optoacoustic neuro-tomography for scalable whole-brain monitoring of calcium indicators

Non-invasive observation of spatiotemporal activity of large neural populations distributed over entire brains is a longstanding goal of neuroscience.We developed a volumetric multispectral optoacoustic tomography platform for imaging neural activation deep in scattering brains.It can record 100 volumetric frames per second across scalable fields of view ranging between 50 and 1000 mm^(3) with respective spatial resolution of 35–200μm.Experiments performed in immobilized and freely swimming larvae and in adult zebrafish brains expressing the genetically encoded calcium indicator GCaMP5G demonstrate,for the first time,the fundamental ability to directly track neural dynamics using optoacoustics while overcoming the longstanding penetration barrier of optical imaging in scattering brains.The newly developed platform thus offers unprecedented capabilities for functional whole-brain observations of fast calcium dynamics;in combination with optoacoustics'well-established capacity for resolving vascular hemodynamics,it could open new vistas in the study of neural activity and neurovascular coupling in health and disease.

Adding fifth dimension to optoacoustic imaging: volumetric time-resolved spectrally enriched tomography

Optoacoustics provides a unique set of capabilities for bioimaging,associated with the intrinsic combination of ultrasound-and light-related advantages,such as high spatial and temporal resolution as well as powerful spectrally enriched imaging contrast in biological tissues.We demonstrate here,for the first time,the acquisition,processing and visualization of five-dimensional optoacoustic data,thus offering unparallel imaging capacities among the current bioimaging modalities.The newly discovered performance is enabled by simultaneous volumetric detection and processing of multispectral data and is further showcased here by attaining time-resolved volumetric blood oxygenation maps in deep human vessels and real-time tracking of contrast agent distribution in a murine model in vivo.

Non-invasive determination of murine placental and foetal functional parameters with multispectral optoacoustic tomography

Despite the importance of placental function in embryonic development,it remains poorly understood and challenging to characterize,primarily due to the lack of non-invasive imaging tools capable of monitoring placental and foetal oxygenation and perfusion parameters during pregnancy.We developed an optoacoustic tomography approach for real-time imaging through entire ~4 cm cross-sections of pregnant mice.Functional changes in both maternal and embryo regions were studied at different gestation days when subjected to an oxygen breathing challenge and perfusion with indocyanine green.Structural phenotyping of the cross-sectional scans highlighted different internal organs,whereas multi-wavelength acquisitions enabled non-invasive label-free spectroscopic assessment of blood-oxygenation parameters in foeto-placental regions,rendering a strong correlation with the amount of oxygen administered.Likewise,the placental function in protecting the embryo from extrinsically administered agents was substantiated.The proposed methodology may potentially further serve as a probing mechanism to appraise embryo development during pregnancy in the clinical setting.

Optical imaging of post-embryonic zebrafish using multi orientation raster scan optoacoustic mesoscopy

Whole-body optical imaging of post-embryonic stage model organisms is a challenging and long sought-after goal.It requires a combination of high-resolution performance and high-penetration depth.Optoacoustic(photoacoustic)mesoscopy holds great promise,as it penetrates deeper than optical and optoacoustic microscopy while providing high-spatial resolution.However,optoacoustic mesoscopic techniques only offer partial visibility of oriented structures,such as blood vessels,due to a limited angular detection aperture or the use of ultrasound frequencies that yield insufficient resolution.We introduce 3601 multi orientation(multi-projection)raster scan optoacoustic mesoscopy(MORSOM)based on detecting an ultra-wide frequency bandwidth(up to 160 MHz)and weighted deconvolution to synthetically enlarge the angular aperture.We report unprecedented isotropic inplane resolution at the 9–17μm range and improved signal to noise ratio in phantoms and opaque 21-day-old Zebrafish.We find that MORSOM performance defines a new operational specification for optoacoustic mesoscopy of adult organisms,with possible applications in the developmental biology of adulthood and aging.

Transmission-reflection optoacoustic ultrasound(TROPUS)computed tomography of small animals

Rapid progress in the development of multispectral optoacoustic tomography techniques has enabled unprecedented insights into biological dynamics and molecular processes in vivo and noninvasively at penetration and spatiotemporal scales not covered by modern optical microscopy methods.Ultrasound imaging provides highly complementary information on elastic and functional tissue properties and further aids in enhancing optoacoustic image quality.We devised the first hybrid transmission–reflection optoacoustic ultrasound(TROPUS)small animal imaging platform that combines optoacoustic tomography with both reflection-and transmission-mode ultrasound computed tomography.The system features full-view cross-sectional tomographic imaging geometry for concomitant noninvasive mapping of the absorbed optical energy,acoustic reflectivity,speed of sound,and acoustic attenuation in whole live mice with submillimeter resolution and unrivaled image quality.Graphics-processing unit(GPU)-based algorithms employing spatial compounding and bent-ray-tracing iterative reconstruction were further developed to attain real-time rendering of ultrasound tomography images in the full-ring acquisition geometry.In vivo mouse imaging experiments revealed fine details on the organ parenchyma,vascularization,tissue reflectivity,density,and stiffness.We further used the speed of sound maps retrieved by the transmission ultrasound tomography to improve optoacoustic reconstructions via two-compartment modeling.The newly developed synergistic multimodal combination offers unmatched capabilities for imaging multiple tissue properties and biomarkers with high resolution,penetration,and contrast.

Localization optoacoustic tomography

Localization-based imaging has revolutionized fluorescence optical microscopy and has also enabled unprecedented ultrasound images of microvascular structures in deep tissues.Herein,we introduce a new concept of localization optoacoustic tomography(LOT)that employs rapid sequential acquisition of three-dimensional optoacoustic images from flowing absorbing particles.We show that the new method enables breaking through the spatial resolution barrier of acoustic diffraction while further enhancing the visibility of structures under limited-view tomographic conditions.Given the intrinsic sensitivity of optoacoustics to multiple hemodynamic and oxygenation parameters,LOT may enable a new level of performance in studying functional and anatomical alterations of microcirculation.

Spiral volumetric optoacoustic tomography visualizes multi-scale dynamics in mice

Imaging dynamics at different temporal and spatial scales is essential for understanding the biological complexity of living organisms,disease state and progression.Optoacoustic imaging has been shown to offer exclusive applicability across multiple scales with excellent optical contrast and high resolution in deep-tissue observations.Yet,efficient visualization of multi-scale dynamics remained difficult with state-of-the-art systems due to inefficient trade-offs between image acquisition time and effective field of view.Herein,we introduce the spiral volumetric optoacoustic tomography technique that provides spectrally enriched highresolution contrast across multiple spatiotemporal scales.In vivo experiments in mice demonstrate a wide range of dynamic imaging capabilities,from three-dimensional high-frame-rate visualization of moving organs and contrast agent kinetics in selected areas to whole-body longitudinal studies with unprecedented image quality.The newly introduced paradigm shift in imaging of multi-scale dynamics adds to the multifarious advantages provided by the optoacoustic technology for structural,functional and molecular imaging.