MR Applications Research Articles

The Impact of Immersive Technologies on Cultural Heritage: A Bibliometric Study of VR, AR, and MR Applications

The Impact of Immersive Technologies on Cultural Heritage: A Bibliometric Study of VR, AR, and MR Applications

Material Attribute Estimation as Part of Telecommunication Augmented Reality, Virtual Reality, and Mixed Reality System: Systematic Review

The integration of material attribute estimation (MAE) within augmented reality, virtual reality, and mixed reality telecommunication systems stands as a pivotal domain, evolving rapidly with the advent of the Tactile Internet. This unifying implementation process has the potential for improvements in the realism and interactivity of immersive environments. The interaction between MAE and the haptic Internet could lead to significant advances in haptic feedback systems, enabling more accurate and responsive user experiences. This systematic review is focused on the intersection of MAE and the Tactile Internet, aiming to find an implementation path between these technologies. Motivated by the potential of the haptic Internet to advance telecommunications, we explore its potential to advance the analysis of material attributes within AR, VR, and MR applications. Through an extensive analysis of current research approaches, including machine learning methods, we explore the possibilities of integrating the TI into MAE. By exploiting haptic and visual properties stored in the materials of 3D objects and using them directly during rendering in remote access scenarios, we propose a conceptual framework that combines data capture, visual representation, processing, and communication in virtual environments.

Magnetic phase transition and large cryogenic magnetocaloric effect in the gallides RE2Rh3Ga (RE = Gd, Dy, Ho, Er)

We herein provide an experimental investigation of the gallides RE2Rh3Ga (RE = Gd, Dy, Ho, Er) regarding their magnetic properties and magnetocaloric effect (MCE). All of these RE2Rh3Ga intermetallic compounds crystallized with the Mg2Ni3Si type structure, space group R–3 m and are ordered magnetically at low temperatures. Large reversible MCEs around their own ordering temperature were observed in all RE2Rh3Ga compounds and their magnetocaloric parameters including the maximum magnetic entropy change, refrigerant capacity, and temperature-averaged entropy change are comparable to those of some recently reported candidate materials with prominent performances, making them considerable for cryogenic MR applications.

67‐4: Late‐News Paper: A New Semi‐transparent OLED‐on‐Silicon Microdisplay Technology Enabling New Optical Design Opportunities for Slim Near‐to‐Eye Optics

Due to their very high resolution and high level of technological maturity, OLED microdisplays are an ideal image generator for VR, AR and MR applications in near‐to‐eye optics. However, due to the silicon‐based backplane, these microdisplays have always been non‐transparent, requiring a complex optical system for integration into an optic. This has a significant impact on the weight, size and overall optical efficiency of the system. In this paper, a novel technology for the realization of semi‐transparent OLED‐on‐silicon microdisplays is presented, which enables completely new optical concepts for near‐to‐eye optics.

Structural and magnetic properties of RE2O2SO4 (RE = Gd, Tb, Dy and Ho) oxides featuring large direct and inverse magnetocaloric effect

In this work, we fabricated the RE2O2SO4 (RE = Gd, Tb, Dy and Ho) oxides by thermal decomposition and systematically determined regarding their structural and magnetic properties, especially of the magnetic phase transition (MPT) and magnetocaloric effect (MCE). All of these RE2O2SO4 oxides are confirmed to crystallize in an orthogonal structure (space group: pmnb); the constituting elements are all distributed uniformly and presented as the RE3+, S6+, and O2− valence states, respectively. They all exhibit a typical cryogenic MPT from paramagnetic to antiferromagnetic (AFM) state together with a field-induced metamagnetic transition (first-order type MPT) from AFM to ferromagnetic state below their MPT temperatures. All of these RE2O2SO4 oxides exhibit considerable direct and inverse cryogenic MCE. The determined direct magnetocaloric parameters of present RE2O2SO4 oxides, especially of Gd2O2SO4 and Ho2O2SO4 oxides, are comparable with most of recently reported RE-based magnetic solids, making them also considerable for practical cryogenic MR applications.

Saliency-Guided Point Cloud Compression for 3D Live Reconstruction

3D modeling and reconstruction are critical to creating immersive XR experiences, providing realistic virtual environments, objects, and interactions that increase user engagement and enable new forms of content manipulation. Today, 3D data can be easily captured using off-the-shelf, specialized headsets; very often, these tools provide real-time, albeit low-resolution, integration of continuously captured depth maps. This approach is generally suitable for basic AR and MR applications, where users can easily direct their attention to points of interest and benefit from a fully user-centric perspective. However, it proves to be less effective in more complex scenarios such as multi-user telepresence or telerobotics, where real-time transmission of local surroundings to remote users is essential. Two primary questions emerge: (i) what strategies are available for achieving real-time 3D reconstruction in such systems? and (ii) how can the effectiveness of real-time 3D reconstruction methods be assessed? This paper explores various approaches to the challenge of live 3D reconstruction from typical point cloud data. It first introduces some common data flow patterns that characterize virtual reality applications and shows that achieving high-speed data transmission and efficient data compression is critical to maintaining visual continuity and ensuring a satisfactory user experience. The paper thus introduces the concept of saliency-driven compression/reconstruction and compares it with alternative state-of-the-art approaches.

Clinical physiology: the crucial role of MRI in evaluation of peripheral artery disease.

Peripheral artery disease (PAD) is a common vascular disease that primarily affects the lower limbs and is defined by the constriction or blockage of peripheral arteries and may involve microvascular dysfunction and tissue injury. Patients with diabetes have more prominent disease of microcirculation and develop peripheral neuropathy, autonomic dysfunction, and medial vascular calcification. Early and accurate diagnosis of PAD and disease characterization are essential for personalized management and therapy planning. Magnetic resonance imaging (MRI) provides excellent soft tissue contrast and multiplanar imaging capabilities and is useful as a noninvasive imaging tool in the comprehensive physiological assessment of PAD. This review provides an overview of the current state of the art of MRI in the evaluation and characterization of PAD, including an analysis of the many applicable MR imaging techniques, describing the advantages and disadvantages of each approach. We also present recent developments, future clinical applications, and future MRI directions in assessing PAD. The development of new MR imaging technologies and applications in preclinical models with translation to clinical research holds considerable potential for improving the understanding of the pathophysiology of PAD and clinical applications for improving diagnostic precision, risk stratification, and treatment outcomes in patients with PAD.

MR Imaging‐Guided High Intensity Focused Ultrasound in the Treatment of Neurologic Disease: Current Applications and Future Directions

MR imaging‐guided focused ultrasound is a revolutionary noninvasive technique with a wide breadth of clinical potential. MR imaging‐guided focused ultrasound uses focused ultrasound energy delivered transcranially to treat a variety of neurologic disease processes. High-intensity focused ultrasound creates sufficient acoustic energy for targeted noninvasive thermal ablation of intracranial soft tissues, with sharply marginated treatment zones overall superior to the established percutaneous ablation techniques. The use of concurrent MR imaging allows highly accurate spatial and thermal guidance, with fine anatomic detail, high soft-tissue contrast, and real-time monitoring of the treatment zone. Here we review the current established applications of MR imaging‐guided focused ultrasound in the treatment of neurologic disease and the relevant anatomic targets for each discussed disease entity, with a focus on essential tremor, Parkinson disease, and neuropathic pain, along with investigative applications and future directions related to this innovative technology.Learning Objective: To provide a comprehensive review of the existing literature on current neurologic applications of MR imaging‐guided high-intensity focused ultrasound and the relevant anatomic targets for each disease entity, discuss investigative applications and future directions for MR imaging‐guided high-intensity focused ultrasound, and increase awareness among providers to promote safe informed use of this relatively newer technology

Magnetic properties and large low-field cryogenic magnetocaloric effect in the divalent europium borate Eu2B2O5 compound

We herein investigated the divalent europium borate Eu2B2O5 compound regarding its structural, magnetic and magnetocaloric properties by means of experimental determinations and first principal calculations. The Eu2B2O5 compound was found to crystallize in a monoclinic structure (P21/c space group) and order ferromagnetically at ground state. A large cryogenic reversible MCE was observed in the Eu2B2O5 compound around 2.7 K. The maximum values of magnetic entropy change of Eu2B2O5 compound reach 13.7, 28.2 and 46.9 J/kgK under the magnetic field changes of 0–1, 0–2, and 0–5 T, respectively. The corresponding values of adiabatic temperature change and refrigerant capacity are obtained to be 3.3, 7.0, and 13.3 K and to be 37.8, 102.5, and 317.3 J/kg. These magnetocaloric parameters, especially under relatively low-field changes, are better than those of the reported candidate materials, which makes the Eu2B2O5 compound attractive for cryogenic MR applications.

Predicting dynamic, motion-related changes in B0 field inthe brain at a 7T MRI using a subject-specific fine-trainedU-net.

Subject movement during the MR examination is inevitable and causes not only image artifacts but also deteriorates the homogeneity of the main magnetic field (B0 ), which is a prerequisite for high quality data. Thus, characterization of changes to B0 , for example induced by patient movement, is important for MR applications that are prone to B0 inhomogeneities. We propose a deep learning based method to predict such changes within the brain from the change of the head position to facilitate retrospective or even real-time correction. A 3D U-net was trained on in vivo gradient-echo brain 7T MRI data. The input consisted of B0 maps and anatomical images at an initial position, and anatomical images at a different head position (obtained by applying a rigid-body transformation on the initial anatomical image). The output consisted of B0 maps at the new head positions. We further fine-trained the network weights to each subject by measuring a limited number of head positions of the given subject, and trained the U-net with these data. Our approach was compared to established dynamic B0 field mapping via interleaved navigators, which suffer from limited spatial resolution and the need for undesirable sequence modifications. Qualitative and quantitative comparison showed similar performance between an interleaved navigator-equivalent method and proposed method. It is feasible to predict B0 maps from rigid subject movement and, when combined with external tracking hardware, this information could be used to improve the quality of MR acquisitions without the use of navigators.

MADRL-Based Joint Edge Caching and Bitrate Selection for Multicategory 360° Video Streaming

360-degree video streaming has gained increasing attraction in the current popular VR, AR, and MR applications, which can provide users with an immersive experience. In tile-based 360-degree video streaming, edge caching and bitrate selection strategies are jointly designed to improve users’ Quality of Experience (QoE), which incorporates video quality and rebuffer. However, the existing QoE-driven approaches use a unified QoE function to guide the decisions of edge caching and bitrate selection, which neglect the impact of video quality and rebuffer on different categories of 360-degree videos, thus failing to provide high average QoE for users. In this paper, we propose a MADRL-based joint edge caching and bitrate selection strategy for multicategory 360-degree video streaming to improve users’ average QoE. The key idea is to employ different edge caching and bitrate selection strategies for different video categories to enable fine-grained performance optimization. Based on multicategory 360-degree video streaming, we first model a joint edge caching and bitrate selection problem as a multi-agent cooperative Markov decision process with the goal of maximizing users’ average QoE. Next, an FoV-aware multi-agent soft actor-critic (FA-MASAC) algorithm is designed to help agents collaboratively learn optimal edge caching and bitrate selection decisions in a distributed way, in which each video category is treated as an agent. Finally, experimental results on real-world datasets show that our proposed strategy can greatly benefit users’ average QoE compared to existing strategies.

Development of AR and MR Applications for Supporting Endovascular Treatment of Cerebral Aneurysms

Development of AR and MR Applications for Supporting Endovascular Treatment of Cerebral Aneurysms

Mendelian Randomization as a Tool for Cardiovascular Research

ImportanceMendelian randomization (MR) is a statistical approach that has become increasingly popular in the field of cardiovascular disease research. It offers a way to infer potentially causal relationships between risk factors and outcomes using observational data, which is particularly important in cases where randomized clinical trials are not feasible or ethical. With the growing availability of large genetic data sets, MR has become a powerful and accessible tool for studying the risk factors for cardiovascular disease.ObservationsMR uses genetic variation associated with modifiable exposures or risk factors to mitigate biases that affect traditional observational study designs. The approach uses genetic variants that are randomly assigned at conception as proxies for exposure to a risk factor, mimicking a randomized clinical trial. By comparing the outcomes of individuals with different genetic variants, researchers may draw causal inferences about the effects of specific risk factors on cardiovascular disease, provided assumptions are met that address (1) the association between each genetic variant and risk factor and (2) the association of the genetic variants with confounders and (3) that the association between each genetic variant and the outcome only occurs through the risk factor. Like other observational designs, MR has limitations, which include weak instruments that are not strongly associated with the exposure of interest, linkage disequilibrium where genetic instruments influence the outcome via correlated rather than direct effects, overestimated genetic associations, and selection and survival biases. In addition, many genetic databases and MR studies primarily include populations genetically similar to European reference populations; improved diversity of participants in these databases and studies is critically needed.Conclusions and RelevanceThis review provides an overview of MR methodology, including assumptions, strengths, and limitations. Several important applications of MR in cardiovascular disease research are highlighted, including the identification of drug targets, evaluation of potential cardiovascular risk factors, as well as emerging methodology. Overall, while MR alone can never prove a causal relationship beyond reasonable doubt, MR offers a rigorous approach for investigating possible causal relationships in observational data and has the potential to transform our understanding of the etiology and treatment of cardiovascular disease.

Magnetic properties and magnetocaloric effect (MCE) in the melt-spun Tm20Ho20Gd20Ni20Al20 amorphous ribbon

We fabricated the Tm20Ho20Gd20Ni20Al20 ribbons by melt-spun technology and determined its glass forming ability (GFA), magnetic properties, magnetic phase transition (MPT) character, and magnetocaloric performance. The Tm20Ho20Gd20Ni20Al20 melt-spun ribbon exhibits fully amorphous nature and excellent GFA. A second order (SO) type MPT from ferromagnetic to paramagnetic was observed around the Curie temperature of 30.3 K. Moreover, considerable MCE and magnetocaloric performance in Tm20Ho20Gd20Ni20Al20 amorphous ribbon were realized with the maximum magnetic entropy change, temperature-averaged entropy change of 10 K lift, and relative cooling powder/refrigerant capacity of 9.4 J/kgK, 9.0 J/kgK, and 527.2/422.1 J/kg under 0–5 T field change, respectively. These magnetocaloric parameters are close to most of the recently reported magnetocaloric materials, which made the Tm20Ho20Gd20Ni20Al20 amorphous HE ribbon amorphous ribbon also of potential for practical cryogenic MR applications.

Mixed Reality in Modern Surgical and Interventional Practice: Narrative Review of the Literature.

Mixed reality (MR) and its potential applications have gained increasing interest within the medical community over the recent years. The ability to integrate virtual objects into a real-world environment within a single video-see-through display is a topic that sparks imagination. Given these characteristics, MR could facilitate preoperative and preinterventional planning, provide intraoperative and intrainterventional guidance, and aid in education and training, thereby improving the skills and merits of surgeons and residents alike. In this narrative review, we provide a broad overview of the different applications of MR within the entire spectrum of surgical and interventional practice and elucidate on potential future directions. A targeted literature search within the PubMed, Embase, and Cochrane databases was performed regarding the application of MR within surgical and interventional practice. Studies were included if they met the criteria for technological readiness level 5, and as such, had to be validated in a relevant environment. A total of 57 studies were included and divided into studies regarding preoperative and interventional planning, intraoperative and interventional guidance, as well as training and education. The overall experience with MR is positive. The main benefits of MR seem to be related to improved efficiency. Limitations primarily seem to be related to constraints associated with head-mounted display. Future directions should be aimed at improving head-mounted display technology as well as incorporation of MR within surgical microscopes, robots, and design of trials to prove superiority.

Two fluorinated thulium complexes as molecular temperature sensors in MR applications.

19F-based magnetic resonance is a powerful tool to overcome several difficulties of standard 1H MR. We present the syntheses and characterization (including cell viability and stability tests) of two Tm3+ complexes. Both complexes allow the detection of temperature (ΔCT = -0.2319 ppm K-1 and -0.2122 ppm K-1) without a reference compound.

Predicting information usefulness in health information identification from modal behaviors

Finding useful health information should be the highest priority when identifying health information. Predicting information usefulness will significantly improve the effectiveness and efficiency of health information identification, which plays a vital role in fighting against misinformation. Modal behaviors, such as gesture and gaze, are promising indicators of usefulness since they deliver a reliable, thorough, natural, and direct process of user cognitive processing. Therefore, this study aimed to use gesture and gaze behaviors to predict whether information is useful for health information identification. Twenty-four college students were recruited to freely search for information using a smartphone to identify the truthfulness of four propositions (two were true and two were false) about public health epidemics. The participants' gesture behavior, gaze behavior, and information usefulness as perceived by themselves were collected. Based on user cognition, the process of information usefulness judgment was placed into two phases: skimming and reading. Thirty-one features derived from modal behaviors in each phase were extracted. Feature optimization based on the Mann-Whitney U test and random forest was performed. Five common algorithms were used to construct information usefulness prediction models, and these models were compared by the F1_score. Finally, dwell time and gaze entropy in the reading phase were the most important gesture and gaze features respectively. BP neural network was selected to build a unimodal model based on gesture, and gradient boosting decision tree was selected to build a unimodal model based on gaze and a multimodal model combining both. These models all achieved F1_score above 77% and were applicable to different scenarios in health information identification. The model based on gesture could satisfy strong technology or legal constrains, the model based on gaze was ideal for AR, MR or metaverse applications, and the model combining both offered an alternative for multimodal human-computer interaction.

Walking With the ISMRM in the Footprints of Our MR History.

Walking With the ISMRM in the Footprints of Our MR History.

Accelerating MR Parameter Mapping Using Nonlinear Compressive Manifold Learning and Regularized Pre-Imaging.

In this study, we present a novel method to reconstruct the MR parametric maps from highly undersampled k-space data. Specifically, we utilize a nonlinear model to sparsely represent the unknown MR parameter-weighted images in high-dimensional feature space. Each image at a specific time point is assumed to belong to a low-dimensional manifold which is learned from training images created based on the parametric model. The final reconstruction is carried out by venturing the sparse representation of the images in the feature space back to the input space, using the pre-imaging technique. Particularly, among an infinite number of solutions that satisfy the data consistency, the one that is closest to the manifold is selected as the desired solution. The underlying optimization problem is solved using kernel trick, sparse coding, and split Bregman iteration algorithm. In addition, both spatial and temporal regularizations are utilized to further improve the reconstruction quality. The proposed method is validated on both phantom and in vivo human brain T2 mapping data. Results suggest that the proposed method is superior to the conventional linear model-based reconstruction methods, in terms of artifact removal and quantitative estimation accuracy. The proposed method could be potentially beneficial for quantitative MR applications.

Mixed Reality in Vascular Surgery - a Scoping Review

"Mixed reality" (MR) allows the projection of virtual objects into the user's field of view through a head-mounted display (HMD). In the interventional and surgical treatment of vascular diseases MR applications could be of future benefit. The following scoping review aims to provide orientation on the current application of the aforementioned technologies in the field of vascular surgery and to define research goals for the future. A systematic literature search was performed in PubMed (MEDLINE) using the search terms "aorta", "intervention", "endovascular intervention", "vascular surgery", "aneurysm", "endovascular", "vascular access", each in combination with "mixed reality" or "augmented reality". The search was performed according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines for scoping reviews. From 547 references 8 relevant studies were identified. The search results could be classified into two categories: (1) MR aimed at information management and improving periprocedural ergonomics (n=3) and (2) MR aimed at intraoperative navigation (n=5). The registration of the physical patient with the virtual object and the tracking of instruments in the MR environment for intraoperative navigation is currently the focus of scientific interest and could be demonstrated on phantom and animal models with technical success. However, the methods presented so far are associated with high infrastructural costs and important limitations. The use of MR in the field of vascular surgery is promising. For the future, alternative, pragmatic registration methods with appropriate quantification of the positional error should be aimed at. The developed software and hardware solutions should be adapted to the requirements of vascular surgery. Electromagnetic instrument tracking appears to be a useful complementary technology for the implementation of MR-assisted navigation.