Miniaturized photoacoustic microscope for multi-segmental spinal cord imaging in freely moving mice.

Long-term and non-narcotic hemodynamic imaging is indispensable for observing factual physiological information of the spinal cord. Unfortunately, achieving label-free, high-resolution, and widefield spinal cord imaging for mice under freely moving conditions is challenging. In this study, we developed a miniaturized photoacoustic microscope along with a corresponding photoacoustic spinal window to realize high-resolution, multi-segmental hemodynamic imaging of the spinal cord for freely moving mice.

Non-telecentric photoacoustic microscopy for multi-scale imaging.

Optical-resolution photoacoustic microscopy (OR-PAM) excels in precisely imaging a biological tissue based on absorption contrast. However, existing OR-PAMs are confined by fixed compromises between spatial resolution and field of view (FOV), preventing the integration of large FOV and local high-resolution within one system. Here, we present a non-telecentric OR-PAM (nTC-PAM) that empowers efficient adaptation of FOV and spatial resolution to match the multi-scale requirement of diverse biological imaging.

High spatiotemporal mapping of cortical blood flow velocity with an enhanced accuracy.

Cerebral blood flow velocity is one of the most essential parameters related to brain functions and diseases. However, most existing mapping methods suffer from either inaccuracy or lengthy sampling time. In this study, we propose a particle-size-related calibration method to improve the measurement accuracy and a random-access strategy to suppress the sampling time.

Wearable photoacoustic watch for humans.

Longitudinal detection of hemodynamic changes based on wearable devices is imperative for monitoring human healthcare. Photoacoustic effect is extremely sensitive to variations in hemoglobin. Therefore, wearable photoacoustic devices are apt to monitor human healthcare via the observation of hemodynamics.

Near-Infrared II Semiconducting Polymer Dots: Chain Packing Modulation and High-Contrast Vascular Imaging in Deep Tissues.

Fluorescence imaging in the second near-infrared (NIR-II) window has attracted considerable interest in investigations of vascular structure and angiogenesis, providing valuable information for the precise diagnosis of early stage diseases. However, it remains challenging to image small blood vessels in deep tissues because of the strong photon scattering and low fluorescence brightness of the fluorophores. Here, we describe our combined efforts in both fluorescent probe design and image algorithm development for high-contrast vascular imaging in deep turbid tissues such as mouse and rat brains with intact skull.

Split Ring Resonator Topology Based Microwave Induced Thermoacoustic Imaging (SRR-MTAI).

Microwave-induced thermoacoustic imaging (MTAI) using low-energy and long-wavelength microwave photons has great potential in detecting deep-seated diseases due to its unique ability of visualizing intrinsic electric properties of tissue in high resolution. However, the low contrast in conductivity between a target (e.g.

Handheld volumetric photoacoustic/ultrasound imaging using an internal scanning mechanism.

Photoacoustic/ultrasound (PA/US) dual-modality imaging has been evolving rapidly for the last two decades. Handheld PA/US probes with different implementations have attracted particular attention due to their convenience and high applicability. However, developing a volumetric dual-modality PA/US imaging probe with a compact design remains a challenge.

Visualization of blood-brain barrier disruption with dual-wavelength high-resolution photoacoustic microscopy.

The blood-brain barrier (BBB) strictly regulates the substance exchange between the vascular network and the central nervous system, and plays a critical role in maintaining normal brain homeostasis. Impaired BBB is often accompanied with the emergence of cerebral diseases and probably further leads to severe neuroinflammation or even neurological degeneration. Hence, there is an urgent need to precisely monitor the impaired BBB to understand its pathogenesis and better guide the enactment of therapeutic strategies.

Photoacoustic microscopy visualizes glioma-induced disruptions of cortical microvascular structure and function.

. Glioma growth may cause pervasive disruptions of brain vascular structure and function. Revealing both structural and functional alterations at a fine spatial scale is challenging for existing imaging techniques, which could confound the understanding of the basic mechanisms of brain diseases.

Multicolor Photoacoustic Volumetric Imaging of Subcellular Structures.

Photoacoustic imaging (PAI) has been widely used in multiscale and multicontrast imaging of biological structures and functions. Optical resolution photoacoustic microscopy (OR-PAM), an emerging submodality of PAI, features high lateral resolution and rich optical contrast, indicating great potential in visualizing cellular and subcellular structures. However, three-dimensional (3D) imaging of subcellular structures using OR-PAM has remained a challenge due to the limited axial resolution.

Detachable head-mounted photoacoustic microscope in freely moving mice.

Optical resolution photoacoustic microscopy (ORPAM) is a promising tool for investigating anatomical and functional dynamics in the cerebral cortex. However, observation in freely moving mice has been a longstanding challenge for ORPAM. In this Letter, we extended ORPAM from anesthetized, head-restrained to awake, freely moving mice by using a detachable head-mounted ORPAM probe.

Dual-model wearable photoacoustic microscopy and electroencephalograph: study of neurovascular coupling in anesthetized and freely moving rats.

Observing microscale neurovascular dynamics under different physiological conditions is of great importance to understanding brain functions and disorders. Here, we report a dual-model wearable device and an auxiliary data processing algorithm to derive neurovascular dynamics. The device integrates high-resolution photoacoustic microscopy and electroencephalography (EEG), which allows observing capillary-level hemodynamics and neural activities in anesthesia and freely moving rats.

Multi-modality photoacoustic/ultrasound imaging based on a commercial ultrasound platform.

Multimodal imaging takes advantage of each modality and has become a recent trend in the field of biomedical imaging. In this Letter, we develop and evaluate an integrated multi-modality imaging system combining photoacoustic computed tomography, optical resolution photoacoustic microscopy, brightness mode, and power Doppler ultrasound imaging on a commercial ultrasonographic platform. Using different imaging modalities enables the hybrid system to recover dense vascular networks and hemodynamic and morphological variations in both superficial and deep tissues.

Light-Controlled Precise Delivery of NIR-Responsive Semiconducting Polymer Nanoparticles with Promoted Vascular Permeability.

The endothelial barrier plays an essential role in health and disease by protecting organs from toxins while allowing nutrients to access the circulation. However, it is the major obstacle that limits the delivery of therapeutic drugs to the diseased tissue. Here, it is reported for the first time that near-infrared (NIR) laser pulses can transiently promote the delivery of semiconducting polymer nanoparticles passing the vascular barrier via photoacoustic-effect-induced accumulation, only by the aid of pulse laser irradiation.

High-resolution in vivo imaging of rhesus cerebral cortex with ultrafast portable photoacoustic microscopy.

Revealing the structural and functional change of microvasculature is essential to match vascular response with neuronal activities in the investigation of neurovascular coupling. The increasing use of rhesus models in fundamental and clinical studies of neurovascular coupling presents an emerging need for a new imaging modality. Here we report a structural and functional cerebral vascular study of rhesus monkeys using an ultrafast, portable, and high resolution photoacoustic microscopic system with a long working distance and a special scanning mechanism to eliminate the relative displacement between the imaging interface and samples.

Photoacoustic Force-Guided Precise and Fast Delivery of Nanomedicine with Boosted Therapeutic Efficacy.

Precise and efficient delivery of nanomedicine to the target site has remained as a major roadblock in advanced cancer treatment. Here, a novel photoacoustic force (PAF)-guided nanotherapeutic system is reported based on a near-infrared (NIR)-absorbing semiconducting polymer (SP), showing significantly improved tumor accumulation and deep tissue penetration for enhanced phototherapeutic efficacy. The accumulation of nanoparticles in 4T1 tumor-bearing mice induced by the PAF strategy displays a fivefold enhancement in comparison with that of the traditional passive targeting pathway, in a significantly shortened time (45 min vs 24 h) with an enhanced penetration depth in tumors.

Progress of clinical translation of handheld and semi-handheld photoacoustic imaging.

Photoacoustic imaging (PAI), featuring rich contrast, high spatial/temporal resolution and deep penetration, is one of the fastest-growing biomedical imaging technology over the last decade. To date, numbers of handheld and semi-handheld photoacoustic imaging devices have been reported with corresponding potential clinical applications. Here, we summarize emerged handheld and semi-handheld systems in terms of photoacoustic computed tomography (PACT), optoacoustic mesoscopy (OAMes), and photoacoustic microscopy (PAM).

Optical resolution photoacoustic computed microscopy.

Optical resolution photoacoustic microscopy (ORPAM) has demonstrated both high resolution and rich contrast imaging of optical chromophores in biologic tissues. To date, sensitivity remains a major challenge for ORPAM, which limits the capability of resolving biologic microvascular networks. In this study, we propose and evaluate a new ORPAM modality termed as optical resolution photoacoustic computed microscopy (ORPACM), through the combination of a two-dimensional laser-scanning system with a medical ultrasonographic platform.

Photoacoustic endoscopy: A progress review.

Endoscopy has been widely used in biomedical imaging and integrated with various optical and acoustic imaging modalities. Photoacoustic imaging (PAI), one of the fastest growing biomedical imaging modalities, is a noninvasive and nonionizing method that owns rich optical contrast, deep acoustic penetration depth, multiscale and multiparametric imaging capability. Hence, it is preferred to miniaturize the volume of PAI and develop an emerged endoscopic imaging modality referred to as photoacoustic endoscopy (PAE).

Fluorination Enhances NIR-II Fluorescence of Polymer Dots for Quantitative Brain Tumor Imaging.

Here, we describe a fluorination strategy for semiconducting polymers for the development of highly bright second near-infrared region (NIR-II) probes. Tetrafluorination yielded a fluorescence QY of 3.2 % for the polymer dots (Pdots), over a 3-fold enhancement compared to non-fluorinated counterparts.

Deep-learning-based motion-correction algorithm in optical resolution photoacoustic microscopy.

In this study, we propose a deep-learning-based method to correct motion artifacts in optical resolution photoacoustic microscopy (OR-PAM). The method is a convolutional neural network that establishes an end-to-end map from input raw data with motion artifacts to output corrected images. First, we performed simulation studies to evaluate the feasibility and effectiveness of the proposed method.

Quantitative investigation of vascular response to mesenteric venous thrombosis using large-field-of-view photoacoustic microscopy.

Mesenteric venous thrombosis (MVT) is one of major causes leading to severe mesenteric ischemia. Vascular network plays an important role during the occurrence and development of MVT. However, there lacks an appropriate imaging method, which features advanced volumetric resolving capability, superior sensitivity to hemoglobin, and ultra-large field-of-view (FOV), to investigate vascular response of MVT.

Assessing the development and treatment of rheumatoid arthritis using multiparametric photoacoustic and ultrasound imaging.

Rheumatoid arthritis (RA), characterized by polyarthritis, is a chronic, systemic and inflammatory autoimmune disease. In this study, we developed a dual-modality multiparametric photoacoustic and ultrasound imaging technique, and successfully derived multiple parameters such as relative concentration of total hemoglobin (C ), ratio of angiogenesis, joint size and area of synovia to assess the development and treatment of RA. We established a model of adjuvant arthritis using a total number of 15 rats and randomly divided them into three groups: (a) targeted group in which the rats received targeted antirheumatic drugs; (b) nontargeted group in which the rats were treated with nontargeted antirheumatic drugs; (c) control group.

Miniaturized Optical Resolution Photoacoustic Microscope Based on a Microelectromechanical Systems Scanning Mirror.

In this paper, we report a miniaturized optical resolution photoacoustic microscopy system based on a microelectromechanical system (MEMS) scanning mirror. A two-dimensional MEMS scanning mirror was used to achieve raster scanning of the excitation optical focus. The wideband photoacoustic signals were detected by a flat ultrasound transducer with a center frequency of 10 MHz and an active area of 2 mm in diameter.

Assessing hemorrhagic shock: Feasibility of using an ultracompact photoacoustic microscope.

Hemorrhagic shock, as an important clinical issue, is regarding as a critical disease with a high mortality rate. Unfortunately, existing clinical technologies are inaccessible to assess the hemorrhagic shock via hemodynamics in microcirculation. Here, we propose an ultracompact photoacoustic microscope to assess hemorrhagic shock using a rat model and demonstrate its clinical feasibility by visualizing buccal microcirculation of healthy volunteers.