Optoacoustic tomography (OAT) and magnetic resonance imaging (MRI) provide highly complementary capabilities for anatomical and functional imaging of living organisms. Herein, we investigate on the feasibility of combining both modalities to render concurrent images. This was achieved by introducing a specifically‐designed copper‐shielded spherical ultrasound array into a preclinical MRI scanner. Phantom experiments revealed that the OAT probe caused minimal distortion in the MRI images, while synchronization of the laser and the MRI pulse sequence enabled defining artifact‐free acquisition windows for OAT. Good dynamic OAT contrast from superparamagnetic iron oxide nanoparticles, a commonly used agent for MRI contrast enhancement, was also observed. The hybrid OAT‐MRI system thus provides an excellent platform for cross‐validating functional readings of both modalities. Overall, this initial study serves to establish the technical feasibility of developing a hybrid OAT‐MRI system for biomedical research.

The FMT/dFRI protocol presented is able to accurately map physiological processes and poses an attractive alternative to MRI for characterizing tumor neoangiogenesis.

Multi-modal imaging is essential for advancing our understanding of brain function and unraveling pathophysiological processes underlying neurological and psychiatric disorders. Magnetic resonance (MR) and optoacoustic (OA) imaging have been shown to provide highly complementary contrasts and capabilities for preclinical neuroimaging. True integration between these modalities can thus offer unprecedented capabilities for studying the rodent brain in action. We report on a hybrid magnetic resonance and optoacoustic tomography (MROT) system for concurrent noninvasive structural and functional imaging of the mouse brain. Volumetric OA tomography was designed as an insert into a high-field MR scanner by integrating a customized MR-compatible spherical transducer array, an illumination module, and a dedicated radiofrequency coil. A tailored data processing pipeline has been developed to mitigate signal crosstalk and accurately register image volumes acquired with T1-weighted, angiography, and blood oxygenation level-dependent (BOLD) sequences onto the corresponding vascular and oxygenation data recorded with the OA modality. We demonstrate the concurrent acquisition of dual-mode anatomical and angiographic brain images with the scanner, as well as real-time functional readings of multiple hemodynamic parameters from animals subjected to oxygenation stress. Our approach combines the functional and molecular imaging advantages of OA with the superb soft-tissue contrast of MR, further providing an excellent platform for cross-validation of functional readings by the two modalities.

Functional magnetic resonance imaging (fMRI) has massively contributed to the understanding of mammalian brain function. However, the origin and interpretation of the blood oxygen level‐dependent (BOLD) signals retrieved by fMRI remain highly disputed. This article reports on the development of a fully hybridized system enabling concurrent functional magnetic resonance optoacoustic tomography (MROT) measurements of stimulus‐evoked brain‐wide sensory responses in mice. The highly complementary angiographic and soft tissue contrasts of both modalities along with simultaneous multi‐parametric readings of stimulus‐evoked hemodynamic responses are leveraged in order to establish unequivocal links between the various counteracting physiological and metabolic processes in the brain. The results indicate that the BOLD signals are highly correlated, both spatially and temporally, with the total hemoglobin readings resolved with volumetric multi‐spectral optoacoustic tomography. Furthermore, the differential oxygenated and deoxygenated hemoglobin optoacoustic readings exhibit superior sensitivity as compared to the BOLD signals when detecting stimulus‐evoked hemodynamic responses. The fully hybridized MROT approach greatly expands the neuroimaging toolset to comprehensively study neurovascular and neurometabolic coupling mechanisms and related diseases.

No abstract

Progress in brain research critically depends on the development of next-generation multi-modal imaging tools capable of capturing transient functional events and multiplexed contrasts noninvasively and concurrently, thus enabling a holistic view of dynamic events in vivo. Here we report on a hybrid magnetic resonance and optoacoustic tomography (MROT) system for murine brain imaging, which incorporates an MR-compatible spherical matrix array transducer and fiber-based light illumination into a 9.4 T small animal scanner. An optimized radiofrequency coil has further been devised for whole-brain interrogation. System’s utility is showcased by acquiring complementary angiographic and soft tissue anatomical contrast along with simultaneous dual-modality visualization of contrast agent dynamics in vivo.

Multimodal imaging increases the value of stand‐alone modalities by enabling simultaneous multiparametric characterization of biological tissues in vivo. Particularly, optoacoustic (OA) tomography has enabled bringing optical imaging advantages to previously unattainable depths and is currently being hybridized with other imaging technologies for enhanced performance. The full potential of these multimodal imaging approaches can only be achieved with dedicated contrast agents ensuring simultaneous measurements and accurate co‐registration of the information provided. Herein, perfluoropentane‐filled nanodroplets are modified, providing excellent contrast in ultrasound imaging, by introducing shell‐embedded additives offering strong contrast in magnetic resonance and OA imaging. Magnetite nanoparticles and indocyanine green (ICG) dye are simultaneously deposited as a multilayer shell on the droplets with the layer‐by‐layer method. This results in sufficiently high amounts of magnetite (0.54 ± 0.08 mg mL−1) and ICG (0.30 ± 0.08 mg mL−1) for efficient magnetic resonance and OA detection, respectively. The high sensitivity achieved with the developed trimodal nanodroplets is first demonstrated in phantom experiments, after which their potential toxic effects, biodistribution, and clearance are examined in vitro and in vivo. Taken together, the obtained results indicate that the developed multilayer polymer shell nanodroplets are efficient hybrid contrast agents for multimodal biomedical imaging applications.

Progress in brain research critically depends on the development of next-generation multi-modal imaging tools that are capable of capturing transient functional events and multiplexed contrasts noninvasively and concurrently. A number of outstanding questions, such as those pertaining to the link between blood-oxygen-level-dependent (BOLD) signaling, oxygen saturation and underlying neural activity, could potentially be addressed by truly integrating several complementary neuroimaging readouts into one hybrid system, thus enabling a holistic view of dynamic events in vivo. Here we developed a hybrid magnetic resonance and optoacoustic tomography (MROT) system for murine brain imaging by incorporating an MR-compatible spherical matrix array transducer and fiber-based light illumination into a 9.4T small animal scanner, whilst further designing an optimized radiofrequency coil for whole-brain interrogation. The utility of the system is demonstrated by acquiring complementary angiographic and soft tissue anatomical contrast along with simultaneous dual-modality visualization of contrast agent dynamics in vivo.