Imaging Of Vasculature Research Articles

Super‐resolution imaging of urethral vasculature in female pigs: Validation of clinical feasibility and accuracy

AbstractThe efficacy and reliability of super‐resolution (SR) imaging for evaluating urethral vasculature (UV) in females remains uncertain. This study evaluates the super ultrasound for grand accuracy and resolution (SUGAR) method, an SR modality, for visualizing UV in female pigs within clinical ultrasound settings, aiming to establish its clinical feasibility and accuracy for potential human application. Female pigs (40–45 kg) were used to investigate UV blood flow dynamics, with data collected via a handheld ultrasound probe at 100 fps. The images were processed using SUGAR to achieve a resolution of <30 µm and validated against computed tomography angiography (CTA) and histopathological analyses. SUGAR demonstrated superior capability in visualizing urethral blood flow compared to CTA, allowing for detailed multiparametric analysis of UV, including fractal dimension, vessel density, tortuosity, diameter, and blood flow velocity. Strong correlations between SUGAR imaging and histopathological findings underscore its potential clinical applicability for diagnosing and managing urological conditions in humans.

Albumin-Chaperoned Deep-NIR Triarylmethane Dyes for High-Contrast In Vivo Imaging and Photothermal Therapy.

Fluorophores absorbing/emitting in the deep near-infrared (deep NIR) spectral region, that is, 800 nm and beyond, hold great promise for in vivo bioimaging, diagnosis, and phototherapy due to deeper tissue penetration. The bottleneck is the lack of bright, stable, and readily synthesized deep NIR fluorophores. Here, it is reported that the albumin-chaperon strategy is a viable one-for-all strategy to address these difficulties. A focused library of deep-NIR absorbing dyes (EA5) is easily synthesized via a two-step cascade. They are neither very stable nor bright in phosphate bufferdue to a propeller-type flexible scaffold. Through screening, EA5_c3 is found to exhibit a high affinity toward bovine serum albumin (BSA). Binding-associated structural rigidification resulted in a gigantic 26-fold fluorescence enhancement. The albumin chaperone also greatly improved the stability of EA5_c3 by shielding the bisbenzannulated triarylmethane core from nucleophilic or oxidative species. The resulting EA5_c3@BSA exhibits high biocompatibility. It offered high-resolution vasculature, lymph systems, tumors, and other tissue imaging with its bright deep NIR emission. At the same time, it exhibits prominent potential in photoacoustic imaging and photothermal treatment of subcutaneous and orthotopic breast tumors. These findings provide insights into robust and high-performance fluorophores with deep NIR regions for theranostic against aggressive cancers.

Correlation Between Photoreceptor and Vascular Parameters in Diabetic Retinopathy Using Adaptive Optics.

This study aimed to investigate correlations between photoreceptor and vascular parameters in varying stages of diabetic retinopathy (DR) using adaptive optics (AO) imaging. In this single-center, prospective cohort study, 29 participants (46 eyes) were classified into control/mild non-proliferative DR (NPDR), moderate/severe NPDR, and proliferative DR. AO images of photoreceptors and retinal vasculature were analyzed, and Spearman's correlation (ρ) was used to assess relationships between photoreceptor density and vascular parameters. Higher cone density was inversely associated with total vessel (ρ = 0.22, P = 0.03) and lumen diameters (ρ = -0.24, P = 0.01), while higher dispersion was associated with total vessel (ρ = 0.19, P = 0.06) and lumen diameters (ρ = 0.21, P = 0.04). These associations were primarily significant in mild NPDR. No significant correlations were found in advanced DR stages. This study underscores intricate neurovascular correlations in early-stage DR, suggesting these parameters may aid in early disease detection. Further research is needed to understand whether similar correlations exist in advanced DR. [Ophthalmic Surg Lasers Imaging Retina 2024;55:XX-XX.].

Innovative optical imaging strategies for monitoring immunotherapy in the tumor microenvironments.

The tumor microenvironment (TME) plays a critical role in cancer progression and response to immunotherapy. Immunotherapy targeting the immune system has emerged as a promising treatment modality, but challenges in understanding the TME limit its efficacy. Optical imaging strategies offer noninvasive, real-time insights into the interactions between immune cells and the TME. This review assesses the progress of optical imaging technologies in monitoring immunotherapy within the TME and explores their potential applications in clinical trials and personalized cancer treatment. This is a comprehensive literature review based on the advances in optical imaging modalities including fluorescence imaging (FLI), bioluminescence imaging (BLI), and photoacoustic imaging (PAI). These modalities were analyzed for their capacity to provide high-resolution, real-time imaging of immune cell dynamics, tumor vasculature, and other critical components of the TME. Optical imaging techniques have shown significant potential in tracking immune cell infiltration, assessing immune checkpoint inhibitors, and visualizing drug delivery within the TME. Technologies like FLI and BLI are pivotal in tracking immune responses in preclinical models, while PAI provides functional imaging with deeper tissue penetration. The integration of these modalities with immunotherapy holds promise for improving treatment monitoring and outcomes. Optical imaging is a powerful tool for understanding the complexities of the TME and optimizing immunotherapy. Further advancements in imaging technologies, combined with nanomaterial-based approaches, could pave the way for enhanced diagnostic accuracy and therapeutic efficacy in cancer treatment.

High‐Speed Hemodynamic Imaging with Low‐Fluence Photoacoustic Microscopy and Self‐Supervised Single Volume Denoising

AbstractPhotoacoustic microscopy (PAM) enables label‐free imaging of the 3D vasculature and functional information with 2D lateral scan. The unique capacity in probing metabolism makes it ideal for animal research and clinical application. However, the high‐excitation power impedes the high‐speed monitoring of hemodynamics due to thermal accumulation and photon damage. To address this challenge, a self‐supervised photoacoustic single volume denoising (PSVD) approach, which combines 3D random sampling and noise augmentation to achieve 6 dB signal‐to‐noise‐ratio and contrast‐to‐noise‐ratio increases for the customized optical‐resolution photoacoustic microscope, is developed. Using PSVD, high‐quality PAM images of the mouse ear are acquired with only 10% fluence of normal excitation. Functional imaging is validated with this PSVD‐empowered low‐fluence PAM. Accurate oxygen saturation maps and high‐contrast flow kymographs are obtained. Moreover, the capability of this approach in the live mouse ear under hypercapnia is demonstrated. Further transformation into clinical imaging with low fluence will broaden the application of PAM.

Ultrafast Power Doppler Ultrasound Enables Longitudinal Tracking of Vascular Changes that Correlate with Immune Response After Radiotherapy.

While immunotherapy shows great promise in patients with triple negative breast cancer, many will not respond to treatment. Radiotherapy has the potential to prime the tumor-immune microenvironment for immunotherapy. However, predicting response is difficult due to tumor heterogeneity across patients, which necessitates personalized medicine strategies that incorporate tumor tracking into the therapeutic approach. Here, we investigated the use of ultrasound (US) imaging of the tumor vasculature to monitor the tumor response to treatment. We utilized ultrafast power doppler US to track the vascular response to radiotherapy over time. We used 4T1 (metastatic) and 67NR (non-metastatic) breast cancer models to determine if US measurements corroborate conventional immunostaining analysis of the tumor vasculature. To evaluate the effects of radiation, tumor volume and vascular index were calculated using US, and the correlation between vascular changes and immune cell infiltration was determined. US tumor measurements and the quantified vascular response to radiation were confirmed with caliper measurements and immunostaining, respectively, demonstrating a proof-of-principle method for non-invasive vascular monitoring. Additionally, we found significant infiltration of CD8 + T cells into irradiated tumors 10 days after radiation, which followed a sustained decline in vascular index and an increase in splenic CD8 + T cells that was first observed 1 day post-radiation. Our findings reveal that ultrafast power doppler US can evaluate changes in tumor vasculature that are indicative of shifts in the tumor-immune microenvironment. This work may lead to improved patient outcomes through observing and predicting response to therapy.

Abstract C016: Optical Techniques to Democratize Intravital Quantification of Metabolic Heterogeneity

Abstract Since metabolic and vascular adaptations are essential for tumor cell survival, a technique capable of tracking metabolic heterogeneity at both the bulk tumor and cellular scales over extended timelines is necessary. To address this technological need, we have developed a multi-scale optical microscope relying on exogenous fluorescent reporters for dynamic spatiotemporal imaging of major metabolic pathways in vivo. This microscope utilizes a low-cost CMOS detector and LEDs for excitation to enable fluorescence microscopy in resource-limited settings. Here, we implement our system to assess changes in bulk tumor and cellular metabolic heterogeneity as vasculature is perturbed. 4T1 breast tumor-bearing mice were treated with combretastatin A-1 (a vascular disruptor), implanted with window chambers, and temporally imaged (n=5/group). Fluorescence imaging and Gabor filter/Djikstra segmentation approaches enabled metabolic and vascular analyses, respectively. We demonstrated the system’s ability to acquire co-registered images of vasculature, morphology, and distinct metabolic endpoints reporting on glucose uptake, fatty acid uptake, and mitochondrial metabolism at both wide-field and high resolutions. At 12 hours post-treatment, the tumors’ metabolism shifted from mitochondrial respiration to glycolysis in avascular regions. Further, we report a higher average vascular density in untreated versus treated mice at 108 hours post-treatment (p<0.05, Kolmogorov-Smirnov test). On exploring the relationship between metabolic activity and vasculature, regions with high local tortuosity in the untreated group exhibited a higher reliance on fatty acid uptake than high tortuosity regions in the treatment group, indicating these cells’ reliance on fatty acids within a complex vascular network. Our multiplexed imaging strategy enables the quantification of tumor metabolism and vasculature over multiple length scales, which could be leveraged to study adaptations following clinical therapies. Citation Format: Enakshi Sunassee. Optical Techniques to Democratize Intravital Quantification of Metabolic Heterogeneity [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C016.

Applications of optical coherence tomography angiography in glaucoma: current status and future directions.

Glaucoma is a leading cause of irreversible blindness worldwide, with its pathophysiology remaining inadequately understood. Among the various proposed theories, the vascular theory, suggesting a crucial role of retinal vasculature deterioration in glaucoma onset and progression, has gained significant attention. Traditional imaging techniques, such as fundus fluorescein angiography, are limited by their invasive nature, time consumption, and qualitative output, which restrict their efficacy in detailed retinal vessel examination. Optical coherence tomography angiography (OCTA) emerges as a revolutionary imaging modality, offering non-invasive, detailed visualization of the retinal and optic nerve head microvasculature, thereby marking a significant advancement in glaucoma diagnostics and management. Since its introduction, OCTA has been extensively utilized for retinal vasculature imaging, underscoring its potential to enhance our understanding of glaucoma's pathophysiology, improving diagnosis, and monitoring disease progression. This review aims to summarize the current knowledge regarding the role of OCTA in glaucoma, particularly its potential applications in diagnosing, monitoring, and understanding the pathophysiology of the disease. Parameters pertinent to glaucoma will be elucidated to illustrate the utility of OCTA as a tool to guide glaucoma management.

Emerging multimodality imaging techniques for the pulmonary circulation.

Pulmonary hypertension (PH) remains a challenging condition to diagnose, classify and treat. Current approaches to the assessment of PH include echocardiography, ventilation/perfusion scintigraphy, cross-sectional imaging using computed tomography and magnetic resonance imaging, and right heart catheterisation. However, these approaches only provide an indirect readout of the primary pathology of the disease: abnormal vascular remodelling in the pulmonary circulation. With the advent of newer imaging techniques, there is a shift toward increased utilisation of noninvasive high-resolution modalities that offer a more comprehensive cardiopulmonary assessment and improved visualisation of the different components of the pulmonary circulation. In this review, we explore advances in imaging of the pulmonary vasculature and their potential clinical translation. These include advances in diagnosis and assessing treatment response, as well as strategies that allow reduced radiation exposure and implementation of artificial intelligence technology. These emerging modalities hold the promise of developing a deeper understanding of pulmonary vascular disease and the impact of comorbidities. They also have the potential to improve patient outcomes by reducing time to diagnosis, refining classification, monitoring treatment response and improving our understanding of disease mechanisms.

Self-stacked small molecules for ultrasensitive, substrate-free Raman imaging in vivo.

Raman spectroscopy using surface-enhanced Raman scattering (SERS) nanoprobes represents an ultrasensitive and high-precision technique for in vivo imaging. Clinical translation of SERS nanoprobes has been hampered by biosafety concerns about the metal substrates used to enhance Raman signals. We report a set of small molecules with bis-thienyl-substituted benzobisthiadiazole structures that enhance Raman signal through self-stacking rather than external substrates. In our technique, called stacking-induced charge transfer-enhanced Raman scattering (SICTERS), the self-stacked small molecules form an ordered spatial arrangement that enables three-dimensional charge transfer between neighboring molecules. The Raman scattering cross-section of SICTERS nanoprobes is 1350 times higher than that of conventional SERS gold nanoprobes of similar particle size. SICTERS outperforms SERS in terms of in vivo imaging sensitivity, resolution and depth. SICTERS is capable of noninvasive Raman imaging of blood and lymphatic vasculatures, which has not been achieved by SERS. SICTERS represents an alternative technique to enhance Raman scattering for guiding the design of ultrasensitive substrate-free Raman imaging probes.

Photon-Counting CT in the Head and Neck: Current Applications and Future Prospects.

Photon-counting detectors (PCDs) represent a major milestone in the evolution of CT imaging. CT scanners using PCD systems have already been shown to generate images with substantially greater spatial resolution, superior iodine contrast-to-noise ratio, and reduced artifact compared with conventional energy-integrating detector-based systems. These benefits can be achieved with considerably decreased radiation dose. Recent studies have focused on the advantages of PCD-CT scanners in numerous anatomic regions, particularly the coronary and cerebral vasculature, pulmonary structures, and musculoskeletal imaging. However, PCD-CT imaging is also anticipated to be a major advantage for head and neck imaging. In this paper, we review current clinical applications of PCD-CT in head and neck imaging, with a focus on the temporal bone, facial bones, and paranasal sinuses; minor arterial vasculature; and the spectral capabilities of PCD systems.

In vivo imaging of microvasculature in human finger skin using SV-OCT

Abstract Speckle variance optical coherence tomography (SV-OCT) enables non-invasive visualization of the three-dimensional vascular information within the microcirculatory tissue bed by utilizing flowing red blood cells as intrinsic contrast agents, without the need for dye injection. This study evaluated the feasibility of using the SV-OCT device for monitoring the microvascular system in human finger skin. An adaptive wavelet Fourier transform filtering algorithm was applied to remove stripe noise from the images of finger vasculature. The results demonstrate that SV-OCT systems can be used to extract the vascular system of finger skin. By employing an adaptive wavelet Fourier transform filtering (AWFTF)algorithm to process the vascular data, stripe noise can be effectively removed, thereby enhancing the imaging quality of the blood vessels.

Virtual-point-based deconvolution for optical-resolution photoacoustic microscopy.

Optical-resolution photoacoustic microscopy (OR-PAM) has been increasingly utilized for in vivo imaging of biological tissues, offering structural, functional, and molecular information. In OR-PAM, it is often necessary to make a trade-off between imaging depth, lateral resolution, field of view, and imaging speed. To improve the lateral resolution without sacrificing other performance metrics, we developed a virtual-point-based deconvolution algorithm for OR-PAM (VP-PAM). VP-PAM has achieved a resolution improvement ranging from 43% to 62.5% on a single-line target. In addition, it has outperformed Richardson-Lucy deconvolution with 15 iterations in both structural similarity index and peak signal-to-noise ratio on an OR-PAM image of mouse brain vasculature. When applied to an in vivo glass frog image obtained by a deep-penetrating OR-PAM system with compromised lateral resolution, VP-PAM yielded enhanced resolution and contrast with better-resolved microvessels.

Nanoscopic imaging of ancient protein and vasculature offers insight into soft tissue and biomolecule fossilization

Fossil bones have been studied by paleontologists for centuries. Despite this, empirical knowledge regarding the progression of biomolecular (soft) tissue diagenesis within ancient bone is limited; this is particularly the case for specimens spanning Pleistocene directly into pre-Ice Age strata. A nanoscopic approach is reported herein that facilitates direct imaging, and thus empirical observation, of soft tissue preservation state. Presented data include the first extensive nanoscopic (up to 150,000× magnification), three-dimensional (3D) images of ancient bone protein and vasculature; chemical signals consistent with collagen protein and membrane lipids, respectively, are also localized to these structures. These findings support the analyzed permafrost bones are not fully fossilized but rather represent subfossil bone tissue as they preserve an underlying collagen framework. Extension of these methods to specimens spanning the geologic record will help reveal changes biomolecular tissues undergo during fossilization and is a potential proxy approach for screening specimen suitability for molecular sequencing.

Imaging and Quantification of the Hepatic Vasculature of Mice Using Ultrafast Doppler Ultrasound.

Non-invasive in vivo imaging of the vasculature is a powerful tool for studying disease mechanisms in rodents. To achieve high sensitivity imaging of the microvasculature using Doppler ultrasound methods, imaging modalities employing the concept of ultrafast imaging are preferred. By increasing the frame rate of the ultrasound scanner to thousands of frames per second, it becomes possible to improve the sensitivity of the blood flow down to 2 mm/s and to obtain functional information about the microcirculation in comparison to a sensitivity of around 1 cm/s in conventional Doppler modes. While Ultrafast Doppler ultrasound (UFUS) imaging has become adopted in neuroscience, where it can capture brain activity through neurovascular coupling, it presents greater challenges when imaging the vasculature of abdominal organs due to larger motions linked to breathing. The liver, positioned anatomically under the diaphragm, is particularly susceptible to out-of-plane movement and oscillating respiratory motion. These artifacts not only adversely affect Doppler imaging but also complicate the anatomical analysis of vascular structures and the computation of vascular parameters. Here, we present a qualitative and quantitative imaging analysis of the hepatic vasculature in mice by UFUS. We identify major anatomical vascular structures and provide graphical illustrations of the hepatic macroscopical anatomy, comparing it to an in-depth anatomical assessment of the hepatic vasculature based on Doppler readouts. Additionally, we have developed a quantification protocol for robust measurements of hepatic blood volume of the microvasculature over time. To contemplate further research, qualitative vascular analysis provides a comprehensive overview and suggests a standardized terminology for researchers working with mouse models of liver disease. Furthermore, it offers the opportunity to apply ultrasound as a non-invasive complementary method to inspect hepatic vascular defects in vivo and measure functional microvascular alterations deep within the organ before unraveling blood vessel anomalies at the micron scale levels using ex vivo staining on tissue sections.

Dual-Functional Nanodroplet for Tumor Vasculature Ultrasound Imaging and Tumor Immunosuppressive Microenvironment Remodeling.

Accurately evaluating tumor neoangiogenesis and conducting precise interventions toward an immune-favorable microenvironment are of significant clinical importance. In this study, a novel nanodroplet termed as the nanodroplet-based ultrasound contrast agent and therapeutic (NDsUCA/Tx) is designed for ultrasound imaging and precise interventions of tumor neoangiogenesis. Briefly, the NDsUCA/Tx shell is constructed from an engineered CMs containing the tumor antigen, vascular endothelial growth factor receptor 1 (VEGFR1) extracellular domain 2-3, and CD93 ligand multimerin 2. The core is composed of perfluorohexane and the immune adjuvant R848. After injection, NDsUCA/Tx is found to be enriched in the tumor vasculature with high expression of CD93. When triggered by ultrasound, the perfluorohexane in NDsUCA/Tx underwent acoustic droplet vaporization and generated an enhanced ultrasound signal. Some microbubbles exploded and the resultant debris (with tumor antigen and R848) together with the adsorbed VEGF are taken up by nearby cells. This cleared the local VEGF for vascular normalization, and also served as a vaccine to activate the immune response. Using a syngeneic mouse model, the satisfactory performance of NDsUCA/Tx in tumor vasculature imaging and immune activation is confirmed. Thus, a multifunctional NDsUCA/Tx is successfully developed for molecular imaging of tumor neoangiogenesis and precise remodeling of the tumor microenvironment.

Far-Red Aggregation-Induced Emission Hydrogel-Reinforced Tissue Clearing for 3D Vasculature Imaging of Whole Lung and Whole Tumor.

Understanding the vascular formation and distribution in metastatic lung tumors is a significant challenge due to autofluorescence, antibody/dye diffusion in dense tumor, and fluorophore stability when exposed to solvent-based clearing agents. Here, an approach is presented that redefines 3D vasculature imaging within metastatic tumor, peritumoral lung tissue, and normal lung. Specifically, a far-red aggregation-induced emission nanoparticle with surface amino groups (termed as TSCN nanoparticle, TSCNNP) is designed for in situ formation of hydrogel (TSCNNP@Gel) inside vasculatures to provide structural support and enhance the fluorescence in solvent-based tissue clearing method. Using this TSCNNP@Gel-reinforced tissue clearing imaging approach, the critical challenges are successfully overcome and comprehensive visualization of the whole pulmonary vasculature up to 2µm resolution is enabled, including its detailed examination in metastatic tumors. Importantly, features of tumor-associated vasculature in 3D panoramic views are unveiled, providing the potential to determine tumor stages, predict tumor progression, and facilitate the histopathological diagnosis of various tumor types.

Gold Nanoclusters as High Resolution NIR-II Theranostic Agents.

In the realm of nanomaterials, atomically precise quasi-molecular gold nanoclusters (AuNCs) play a prime role due to their unique, stable, and highly tunable optical properties. They are extensively structure-engineered for modulation of surface electronic states toward long wavelength photoluminescence, particularly in the NIR-II (1000 to 1700 nm) window. Contrast agents with NIR-II emission can potentially transform optical imaging in terms of higher spatial resolution, deeper tissue penetration, and reduced tissue autofluorescence. These advantages allow real-time imaging in living organisms for observing disease progression and treatment response. In this short review, we discuss origin of NIR-II emission in rationally designed AuNCs and their application toward high resolution imaging of vasculatures and hard and soft tissue structures for identification of pathological conditions such as stroke and injury. Further, recent employment of these AuNCs in the rapidly growing field of tumor theranostics is also summarized. Final remarks are provided on the scope for improvement in their optical properties and persisting challenges for clinical translation.

Facial vascular visualization enhancement based on optical detection technology.

This study aims to develop a facial vascular enhancement imaging system and analyze vascular distribution in the facial region to assess its potential in preventing unintended intravascular injections during cosmetic facial filling procedures. A facial vascular enhancement imaging system based on optical detection technology was designed, and volunteers were recruited. The system was utilized to detect and analyze vascular distribution in various anatomical regions of the faces. The vascular visualization-enhanced images generated by the system were compared with visible light images to validate the vascular visualization capability of the system. Additionally, the reliability of vascular visualization was assessed by comparing the observed vascular patterns in the vascular visualization-enhanced images with those in near-infrared light images. Thirty volunteers were recruited. The vascular visualization-enhanced images produced by the system demonstrated a significant capacity to identify vascular morphology and yielded a higher vessel count compared to visible light images, particularly in the frontal, orbital, perioral, mental, temporal, cheek, and parotid masseter regions (p < 0.05). The temporal region exhibited the highest vascular density, followed by the cheek region and then the frontal region. Reliability analysis of vascular visualization enhancement indicated that the system's imaging of facial vasculature not only demonstrated reliability but also enhanced physicians' visual perception. Blood vessel distribution varies across facial regions. The facial vascular enhancement imaging system facilitates real-time and clear visualization of facial vasculature, offering immediate visual feedback to surgeons. This innovation holds promise for enhancing the safety and effectiveness of facial filling procedures.

Improving Three-Photon Fluorescence of Near-Infrared Quantum Dots for Deep Brain Imaging by Suppressing Biexciton Decay.

Three-photon fluorescence microscopy (3PFM) is a promising brain research tool with submicrometer spatial resolution and high imaging depth. However, only limited materials have been developed for 3PFM owing to the rigorous requirement of the three-photon fluorescence (3PF) process. Herein, under the guidance of a band gap engineering strategy, CdTe/CdSe/ZnS quantum dots (QDs) emitting in the near-infrared window are designed for constructing 3PF probes. The formation of type II structure significantly increased the three-photon absorption cross section of QDs and caused the delocalization of electron-hole wave functions. The time-resolved transient absorption spectroscopy confirmed that the decay of biexcitons was significantly suppressed due to the appropriate band gap alignment, which further enhanced the 3PF efficiency of QDs. By utilizing QD-based 3PF probes, high-resolution 3PFM imaging of cerebral vasculature was realized excited by a 1600 nm femtosecond laser, indicating the possibility of deep brain imaging with these 3PF probes.