The Effects of Free Breathing on Cerebral Venous Flow: A Real-Time Phase Contrast MRI Study in Healthy Adults.

Quantifying the effects of free breathing on cerebral venous flow is crucial for understanding cerebral circulation mechanisms and clinical applications. Unlike conventional cine phase-contrast MRI sequences (CINE-PC), real-time phase-contrast MRI sequences (RT-PC) can provide a continuous beat-to-beat flow signal that makes it possible to quantify the effect of breathing on cerebral venous flow. In this study, we examined 28 healthy human participants, comprising of 14 males and 14 females. Blood flows in the right/left internal jugular veins in the extracranial plane and the superior sagittal sinus (SSS) and straight sinus in the intercranial plane were quantified using CINE-PC and RT-PC. The first objective of this study was to determine the accuracy of RT-PC in quantifying cerebral venous flow, relative to CINE-PC. The second, and main objective, was to quantify the effect of free breathing on cerebral venous flow, using a time-domain multiparameter analysis method. Our results showed that RT-PC can accurately quantify cerebral venous flow with a 2 × 2 mm2 spatial resolution and 75 ms/image time resolution. The mean flow rate, amplitude, stroke volume, and cardiac period of cerebral veins were significantly higher from the mid-end phase of expiration to the mid-end phase of inspiration. Breathing affected the mean flow rates in the jugular veins more than those in the SSS and straight sinus. Furthermore, the effects of free breathing on the flow rate of the left and right jugular veins were not synchronous. These new findings provide a useful reference for better understanding the mechanisms of cerebral circulation.

Real-time imaging of Arc/Arg3.1 transcription ex vivo reveals input-specific immediate early gene dynamics.

The ability of neurons to process and store salient environmental features underlies information processing in the brain. Long-term information storage requires synaptic plasticity and regulation of gene expression. While distinct patterns of activity have been linked to synaptic plasticity, their impact on immediate early gene (IEG) expression remains poorly understood. The activity regulated cytoskeleton associated (Arc) gene has received wide attention as an IEG critical for long-term synaptic plasticity and memory. Yet, to date, the transcriptional dynamics of Arc in response to compartment and input-specific activity is unclear. By developing a knock-in mouse to fluorescently tag Arc alleles, we studied real-time transcription dynamics after stimulation of dentate granule cells (GCs) in acute hippocampal slices. To our surprise, we found that Arc transcription displayed distinct temporal kinetics depending on the activation of excitatory inputs that convey functionally distinct information, i.e., medial and lateral perforant paths (MPP and LPP, respectively). Moreover, the transcriptional dynamics of Arc after synaptic stimulation was similar to direct activation of GCs, although the contribution of ionotropic glutamate receptors, L-type voltage-gated calcium channel, and the endoplasmic reticulum (ER) differed. Specifically, we observed an ER-mediated synapse-to-nucleus signal that supported elevations in nuclear calcium and, thereby, rapid induction of Arc transcription following MPP stimulation. By delving into the complex excitation-transcription coupling for Arc, our findings highlight how different synaptic inputs may encode information by modulating transcription dynamics of an IEG linked to learning and memory.

Unveiling the Dynamic Electrocatalytic Activity of Online Synthesized Bimetallic Nanocatalysts via Electrochemiluminescence Microscopy.

Effective bimetallic nanoelectrocatalysis demands precise control of composition, structure, and understanding catalytic mechanisms. To address these challenges, we employ a two-in-one approach, integrating online synthesis with real-time imaging of bimetallic Au@Metal core-shell nanoparticles (Au@M NPs) via electrochemiluminescence microscopy (ECLM). Within 120 s, online electrodeposition and in situ catalytic activity screening alternate. ECLM captures transient faradaic processes during potential switches, visualizes electrochemical processes in real-time, and tracks catalytic activity dynamics at the single-particle level. Analysis using ECL photon flux density eliminates size effects and yields quantitative electrocatalytic activity results. Notably, a nonlinear activity trend corresponding to the shell metal to Au surface atomic ratio is discerned, quantifying the optimal surface component ratio of Au@M NPs. This approach offers a comprehensive understanding of catalytic behavior during the deposition process with high spatiotemporal resolution, which is crucial for tailoring efficient bimetallic nanocatalysts for diverse applications.

Altered anterograde axonal transport of mitochondria in cultured striatal neurons of a knock-in mouse model of Huntington's disease.

Huntington's disease (HD) is a progressive genetic neurodegenerative disease caused by an abnormal expansion of a cytosine-adenine-guanine trinucleotide repeat in the huntingtin gene. One pathological feature of HD is neuronal loss in the striatum. Despite many efforts, mechanisms underlying neuronal loss in HD striatum remain elusive. It was suggested that the mutant huntingtin protein interacts mitochondrial proteins and causes mitochondrial dysfunction in striatal neurons. However, whether axonal transport of mitochondria is altered in HD striatal neurons remains controversial. Here, we examined axonal transport of single mitochondria labelled with Mito-DsRed2 in cultured striatal neurons of zQ175 knock-in mice (a knock-in mouse model of HD). We observed decreased anterograde axonal transport of proximal mitochondria in HD striatal neurons compared with wild-type (WT) striatal neurons. Decreased anterograde transport in HD striatal neurons was prevented by overexpressing mitochondrial Rho GTPase 1 (Miro1). Our results offer a new insight into mechanisms underlying neuronal loss in the striatum in HD.

High-resolution spiral real-time cardiac cine imaging with deep learning-based rapid image reconstruction and quantification.

The objective of the current study was to develop and evaluate a DEep learning-based rapid Spiral Image REconstruction (DESIRE) and deep learning (DL)-based segmentation approach to quantify the left ventricular ejection fraction (LVEF) for high-resolution spiral real-time cine imaging, including 2D balanced steady-state free precession imaging at 1.5 T and gradient echo (GRE) imaging at 1.5 and 3 T. A 3D U-Net-based image reconstruction network and 2D U-Net-based image segmentation network were proposed and evaluated. Low-rank plus sparse (L+S) served as the reference for the image reconstruction network and manual contouring of the left ventricle was the reference of the segmentation network. To assess the image reconstruction quality, structural similarity index, peak signal-to-noise ratio, normalized root-mean-square error, and blind grading by two experienced cardiologists (5: excellent; 1: poor) were performed. To assess the segmentation performance, quantification of the LVEF on GRE imaging at 3 T was compared with the quantification from manual contouring. Excellent performance was demonstrated by the proposed technique. In terms of image quality, there was no difference between L+S and the proposed DESIRE technique. For quantification analysis, the proposed DL method was not different to the manual segmentation method (p > 0.05) in terms of quantification of LVEF. The reconstruction time for DESIRE was ~32 s (including nonuniform fast Fourier transform [NUFFT]) per dynamic series (40 frames), while the reconstruction time of L+S with GPU acceleration was approximately 3 min. The DL segmentation takes less than 5 s. In conclusion, the proposed DL-based image reconstruction and quantification techniques enabled 1-min image reconstruction for the whole heart and quantification with automatic reconstruction and quantification of the left ventricle function for high-resolution spiral real-time cine imaging with excellent performance.

Real-time imaging of intracellular deformation dynamics in vibrated adherent cell cultures.

Mechanical vibration has been shown to regulate cell proliferation and differentiation in vitro and in vivo. However, the mechanism of its cellular mechanotransduction remains unclear. Although the measurement of intracellular deformation dynamics under mechanical vibration could reveal more detailed mechanisms, corroborating experimental evidence is lacking due to technical difficulties. In this study, we aimed to propose a real-time imaging method of intracellular structure deformation dynamics in vibrated adherent cell cultures and investigate whether organelles such as actin filaments connected to a nucleus and the nucleus itself show deformation under horizontal mechanical vibration. The proposed real-time imaging was achieved by conducting vibration isolation and making design improvements to the experimental setup; using a high-speed and high-sensitivity camera with a global shutter; and reducing image blur using a stroboscope technique. Using our system, we successfully produced the first experimental report on the existence of the deformation of organelles connected to a nucleus and the nucleus itself under horizontal mechanical vibration. Furthermore, the intracellular deformation difference between HeLa and MC3T3-E1 cells measured under horizontal mechanical vibration agrees with the prediction of their intracellular structure based on the mechanical vibration theory. These results provide new findings about the cellular mechanotransduction mechanism under mechanical vibration.

The future of CMR: All-in-one vs. real-time CMR (Part 2).

Cardiac Magnetic Resonance (CMR) protocols can be lengthy and complex, which has driven the research community to develop new technologies to make these protocols more efficient and patient-friendly. Two different approaches to improving CMR have been proposed, specifically "all-in-one" CMR, where several contrasts and/or motion states are acquired simultaneously, and "real-time" CMR, in which the examination is accelerated to avoid the need for breathholding and/or cardiac gating. The goal of this two-part manuscript is to describe these two different types of emerging rapid CMR protocols. To this end, the vision of all-in-one and real-time imaging are described, along with techniques which have been devised and tested along the pathway of clinical implementation. The pros and cons of the different methods are presented, and the remaining open needs of each are detailed. Part 1 tackles the "All-in-One" approaches, and Part 2 focuses on the "Real-Time" approaches along with an overall summary of these emerging methods.

The future of cardiovascular magnetic resonance: All-in-one vs. real-time (Part 1).

Cardiovascular magnetic resonance (CMR) protocols can be lengthy and complex, which has driven the research community to develop new technologies to make these protocols more efficient and patient-friendly. Two different approaches to improving CMR have been proposed, specifically "all-in-one" CMR, where several contrasts and/or motion states are acquired simultaneously, and "real-time" CMR, in which the examination is accelerated to avoid the need for breathholding and/or cardiac gating. The goal of this two-part manuscript is to describe these two different types of emerging rapid CMR. To this end, the vision of each is described, along with techniques which have been devised and tested along the pathway of clinical implementation. The pros and cons of the different methods are presented, and the remaining open needs of each are detailed. Part 1 will tackle the "all-in-one" approaches, and Part 2 the "real-time" approaches along with an overall summary of these emerging methods.

Introducing ARTiMiS: A Low-Cost Flow Imaging Microscope for Microalgal Monitoring.

Manual microscopy is the gold standard for phytoplankton monitoring in diverse engineered and natural environments. However, it is both labor-intensive and requires specialized training for accuracy and consistency, and therefore difficult to implement on a routine basis without significant time investment. Automation can reduce this burden by simplifying the measurement to a single indicator (e.g., chlorophyll fluorescence) measurable by a probe, or by processing samples on an automated cytometer for more granular information. The cost of commercially available flow imaging cytometers, however, poses a steep financial barrier to adoption. To overcome these labor and cost barriers, we developed ARTiMiS: the Autonomous Real-Time Microbial 'Scope. The ARTiMiS is a low-cost flow imaging microscopy-based platform with onboard software capable of providing taxonomically resolved quantitation of phytoplankton communities in real-time. ARTiMiS leverages novel multimodal imaging and onboard machine learning-based data processing that is currently optimized for a curated and expandable database of industrially relevant microalgae. We demonstrate its operational limits, performance in identification of laboratory-cultivated microalgae, and potential for continuous monitoring of complex microalgal communities in full-scale industrial cultivation systems.

Improving the diagnosis and treatment of congenital heart disease through the combination of three-dimensional echocardiography and image guided surgery.

OBJECTIVE: The paper aimed to improve the accuracy limitations of traditional two-dimensional ultrasound and surgical procedures in the diagnosis and management of congenital heart disease (chd), and to improve the diagnostic and therapeutic level of chd. METHOD: This article first collected patient data through real-time imaging and body surface probes, and then diagnosed 150 patients using three-dimensional echocardiography. In order to verify the effectiveness of the combination therapy, 60 confirmed patients were divided into a control group and an experimental group. The control group received conventional two-dimensional ultrasound and surgical treatment, while the experimental group received three-dimensional ultrasound and image guided surgical treatment. RESULT: In the second diagnosis, the diagnostic accuracy of type 1, type 2, and type 3 in the control group was 84.21%, 84.02%, and 83.38%, respectively. The diagnostic accuracy rates of type 1, type 2, and type 3 in the experimental group were 92.73%, 92.82%, and 92.83%, respectively. In the control group, 2 males and 1 female experienced heart failure after surgery. However, in the experimental group, 0 males and 0 females experienced heart failure after surgery. CONCLUSION: The combination of three-dimensional echocardiography and image guided surgery can improve diagnostic accuracy and surgical treatment effectiveness, thereby reducing risks and complications, and improving surgical success rate.

EMEMI: An interference-free mini-incubator with integrated electric and magnetic field exposure for real-time microscopic imaging of field effects.

Uninterrupted microscopic observation and real-time imaging of cell behavior during exposure to the stimulus, for example, electric and/or magnetic fields, especially for periods of several days, has been a challenge in experimental bioelectromagnetics due to a lack of proper gas/temperature conditions outside the incubator. Conventional mini-incubators might suffer from stray fields produced by heating elements. We report an in vitro electric and magnetic fields (EMF) exposure system embedded inside a novel under-the-microscope mini-CO2 -incubator with a unique design to avoid electromagnetic interference from the heating and circulation functions while ensuring the requisite temperature. A unique, reconfigurable array of electrodes and/or coils excited by calculated current distributions among array elements is designed to provide excellent field uniformity and controllable linear or circular polarization (even at very low frequencies) of the EMF within the cell culture. Using standard biochemical assays, long-term cell viability has been verified and compared with a conventional incubator. Cell orientation/migration in three-dimensional culture made of collagen-hydrogels has been successfully observed in vitro, in long-term, and in real-time under the influence of DC electric fields with the device.

Intraoperative Echocardiography: Guide to Decision-Making.

PURPOSE OF REVIEW: This review aims to provide a concise overview of key recommendations, with a specific focus on common challenges faced by intraoperative echocardiographers when dealing with frequently encountered valvular pathologies and mechanical circulatory support. It offers valuable insights for medical practitioners in this field. RECENT FINDINGS: The American Society of Echocardiography (ASE) and the American College of Cardiology/American Heart Association (ACC/AHA) have released updated comprehensive guidelines for the use of transesophageal echocardiography (TEE) for the assessment of cardiac structures and implanted devices to help guide intraoperative decision-making. Transesophageal echocardiography (TEE) is a regularly employed intraoperative diagnostic and monitoring tool, offering various modalities for the rapid evaluation of valvular and aortic pathology, hemodynamic disturbances, and cardiac function. It is particularly valuable in assessing and placing mechanical circulatory support (MCS) devices, providing views often challenging to obtain through transthoracic echocardiography. Additionally, intraoperative TEE can be used for decision-making in patients with valvular disease allowing incorporation of patient-specific and situational factors. Echocardiographers can employ this information in real-time to help guide surgical treatment selection such as repair, replacement, or deferral of intervention.

Application of Self-Attention Generative Adversarial Network for Electromagnetic Imaging in Half-Space.

In this paper, we introduce a novel artificial intelligence technique with an attention mechanism for half-space electromagnetic imaging. A dielectric object in half-space is illuminated by TM (transverse magnetic) waves. Since measurements can only be made in the upper space, the measurement angle will be limited. As a result, we apply a back-propagation scheme (BPS) to generate an initial guessed image from the measured scattered fields for scatterer buried in the lower half-space. This process can effectively reduce the high nonlinearity of the inverse scattering problem. We further input the guessed images into the generative adversarial network (GAN) and the self-attention generative adversarial network (SAGAN), respectively, to compare the reconstruction performance. Numerical results prove that both SAGAN and GAN can reconstruct dielectric objects and the MNIST dataset under same measurement conditions. Our analysis also reveals that SAGAN is able to reconstruct electromagnetic images more accurately and efficiently than GAN.

Electrogenerated Chemiluminescence Imaging of Single-Atom Nanocatalysts.

Single-atom catalysts (SACs), distinguished by their maximum atom efficiency and precise control over the coordination and electronic properties of individual atoms, show great promise in electrocatalysis. Gaining a comprehensive understanding of the electrochemical performance of SACs requires the screening of electron transfer process at micro/nano scale. This research pioneers the use of electrogenerated chemiluminescence microscopy (ECLM) to observe the electrocatalytic reactions at individual SACs. It boasts sensitivity at the single photon level and temporal resolution down to 100 ms, enabling real-time capture of the electrochemical behavior of individual SACs during potential sweeping. Leveraging the direct correlation between ECL emission and heterogeneous electron transfer processes, we introduced photon flux density for quantitative analysis, unveiling the electrocatalytic efficiency of individual SACs. This approach systematically reveals the relationship between SACs based on different metal atoms and their peroxidase (POD)-like activity. The outcomes contribute to a fundamental understanding of SACs and pave the way for designing SACs with diverse technological and industrial applications.

Tracking the Replication-Competent Zika Virus with Tetracysteine-Tagged Capsid Protein in Living Cells.

Real-time imaging of viruses in living cells considerably facilitates the study of virus-host interactions. However, generating a fluorescently labeled recombinant virus is challenging, especially for Zika virus (ZIKV), which causes microcephaly in neonates. The monocistronic nature of the ZIKV genome represents a major challenge for generating a replication-competent genetically engineered ZIKV suitable for real-time imaging. Here, we generated a fluorescent ZIKV by introducing the biarsenical tetracysteine (TC) tag system. After separately inserting the TC tag at six sites in the capsid protein, we found that only when we inserted the TC tag at the site of amino acids 27/28 (AA27/28, or TC27) could the genetically engineered ZIKV be rescued. Importantly, the TC27 ZIKV is characterized as replication and infection competent. After labeling the TC tag with the fluorescent biarsenical reagents, we visualized the dynamic nuclear import behavior of the capsid protein. In addition, using the single-particle tracking technology, we acquired real-time imaging evidence that ZIKV moved along the cellular filopodia and entered into the cytoplasm via endocytosis. Thus, we provide a feasible strategy to generate a replication-competent TC-tagged ZIKV for real-time imaging, which should greatly facilitate the study of ZIKV-host interactions in living cells. IMPORTANCE Zika virus (ZIKV) is the mosquito-borne enveloped flavivirus that causes microcephaly in neonates. While real-time imaging plays a critical role in dissecting viral biology, no fluorescent, genetically engineered ZIKV for single-particle tracking is currently available. Here, we generated a replication-competent genetically engineered ZIKV by introducing the tetracysteine (TC) tag into its capsid protein. After labeling the TC tag with the fluorescent biarsenical reagents, we visualized the nuclear import behavior of the capsid protein and the endocytosis process of single ZIKV particle. Taken together, these results demonstrate a fluorescent labeling strategy to track the ZIKV-host interactions at both the protein level and the viral particle level. Our replication-competent TC27 ZIKV should open an avenue to study the ZIKV-host interactions and may provide applications for antiviral screening.

Live-view 4D GRASP MRI: A framework for robust real-time respiratory motion tracking with a sub-second imaging latency.

PURPOSE: To propose a framework called live-view golden-angle radial sparse parallel (GRASP) MRI for low-latency and high-fidelity real-time volumetric MRI. METHODS: Live-view GRASP MRI has two stages. The first one is called an off-view stage and the second one is called a live-view stage. In the off-view stage, 3D k-space data and 2D navigators are acquired alternatively using a new navi-stack-of-stars sampling scheme. A 4D motion database is then generated that contains time-resolved MR images at a sub-second temporal resolution, and each image is linked to a 2D navigator. In the live-view stage, only 2D navigators are acquired. At each time point, a live-view 2D navigator is matched to all the off-view 2D navigators. A 3D image that is linked to the best-matched off-view 2D navigator is then selected for this time point. This framework places the typical acquisition and reconstruction burden of MRI in the off-view stage, enabling low-latency real-time 3D imaging in the live-view stage. The accuracy of live-view GRASP MRI and the robustness of 2D navigators for characterizing respiratory variations and/or body movements were assessed. RESULTS: Live-view GRASP MRI can efficiently generate real-time volumetric images that match well with the ground-truth references, with an imaging latency below 500 ms. Compared to 1D navigators, 2D navigators enable more reliable characterization of respiratory variations and/or body movements that may occur throughout the two imaging stages. CONCLUSION: Live-view GRASP MRI represents a novel, accurate, and robust framework for real-time volumetric imaging, which can potentially be applied for motion adaptive radiotherapy on MRI-Linac.

Motion-resolved real-time 4D flow MRI with low-rank and subspace modeling.

PURPOSE: To develop a new motion-resolved real-time four-dimensional (4D) flow MRI method, which enables the quantification and visualization of blood flow velocities with three-directional flow encodings and volumetric coverage without electrocardiogram (ECG) synchronization and respiration control. METHODS: An integrated imaging method is presented for real-time 4D flow MRI, which encompasses data acquisition, image reconstruction, and postprocessing. The proposed method features a specialized continuous ( k , t ) $$ \left(\mathbf{k},t\right) $$ -space acquisition scheme, which collects two sets of data (i.e., training data and imaging data) in an interleaved manner. By exploiting strong spatiotemporal correlation of 4D flow data, it reconstructs time-series images from highly-undersampled ( k , t ) $$ \left(\mathbf{k},t\right) $$ -space measurements with a low-rank and subspace model. Through data-binning-based postprocessing, it constructs a five-dimensional dataset (i.e., x-y-z-cardiac-respiratory), from which respiration-dependent flow information is further analyzed. The proposed method was evaluated in aortic flow imaging experiments with ten healthy subjects and two patients with atrial fibrillation. RESULTS: The proposed method achieves 2.4 mm isotropic spatial resolution and 34.4 ms temporal resolution for measuring the blood flow of the aorta. For the healthy subjects, it provides flow measurements in good agreement with those from the conventional 4D flow MRI technique. For the patients with atrial fibrillation, it is able to resolve beat-by-beat pathological flow variations, which cannot be obtained from the conventional technique. The postprocessing further provides respiration-dependent flow information. CONCLUSION: The proposed method enables high-resolution motion-resolved real-time 4D flow imaging without ECG gating and respiration control. It is able to resolve beat-by-beat blood flow variations as well as respiration-dependent flow information.

Real-Time and Delayed Imaging of Tissue and Effects of Prostate Tissue Ablation.

PURPOSE OF REVIEW: Prostate ablation is increasingly being utilized for the management of localized prostate cancer. There are several energy modalities with varying mechanism of actions which are currently used for prostate ablation. Prostate ablations, whether focal or whole gland, are performed under ultrasound and/or MRI guidance for appropriate treatment plan execution and monitoring. A familiarity with different intraoperative imaging findings and expected tissue response to these ablative modalities is paramount. In this review, we discuss the intraoperative, early, and delayed imaging findings in prostate from the effects of prostate ablation. RECENT FINDINGS: The monitoring of ablation both during and after the therapy became increasingly important due to the precise targeting of the target tissue. Recent findings suggest that real-time imaging techniques such as MRI or ultrasound can provide anatomical and functional information, allowing for precise ablation of the targeted tissue and increasing the effectiveness and precision of prostate cancer treatment. While intraprocedural imaging findings are variable, the follow-up imaging demonstrates similar findings across various energy modalities. MRI and ultrasound are two of the frequently used imaging techniques for intraoperative monitoring and temperature mapping of important surrounding structures. Follow-up imaging can provide valuable information about ablated tissue, including the success of the ablation, presence of residual cancer or recurrence after the ablation. It is critical and helpful to understand the imaging findings during the procedure and at different follow-up time periods to evaluate the procedure and its outcome.

MR guided cardiac ablation: how to build an interventional magnetic resonance suite and what's the role of the imaging.

Magnetic resonance (MR) represents a new interesting imaging approach for guiding electrophysiology (EP)-based ablation procedures of atrial flutter and typical atrial fibrillation. This new approach permits to reach good results if compared with conventional EP ablation. Tissue characterization by MR permits to detect cardiac anatomy and pathological substrate like myocardial scars well visualized with late gadolinium enhancement (LGE) sequences. Intra-procedural imaging is useful to real-time follow the catheter during the ablation procedure and at the same time to visualize cardiac anatomy in addition to understanding if the ablation is correctly performed using oedema sequences. Performing cardiac ablations inside an MR room permits to reduce radiation exposure and occupational illnesses.

Low-field 0.55 T MRI evaluation of the fetus.

Fetal magnetic resonance imaging (MRI) is an important adjunct modality for the evaluation of fetal abnormalities. Recently, low-field MRI systems at 0.55 Tesla have become available which can produce images on par with 1.5 Tesla systems but with lower power deposition, acoustic noise, and artifact. In this article, we describe a technical innovation using low-field MRI to perform diagnostic quality fetal MRI.