Virtual Objects Research Articles

Countering Calcium Blooming With Personalized Contrast Media Injection Protocols: The 1-2-3 Rule for Photon-Counting Detector CCTA.

Photon-counting detector computed tomography (PCD-CT) enables spectral data acquisition of CT angiographies allowing for reconstruction of virtual monoenergetic images (VMIs) in routine practice. Specifically, it has potential to reduce the blooming artifacts associated with densely calcified plaques. However, calcium blooming and iodine attenuation are inversely affected by energy level (keV) of the VMIs, creating a challenge for contrast media (CM) injection protocol optimization. A pragmatic and simple rule for calcium-dependent CM injection protocols is investigated and proposed for VMI-based coronary CT angiography with PCD-CT. A physiological circulation phantom with coronary vessels including calcified lesions (maximum CT value >700 HU) with a 50% diameter stenosis was injected into at iodine delivery rates (IDRs) of 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, and 3.0 g I/s. Images were acquired using a first-generation dual-source PCD-CT and reconstructed at various VMI levels (between 45 and 190 keV). Iodine attenuation in the coronaries was measured at each IDR for each keV, and blooming artifacts from the calcified lesions were assessed including stenosis grading error (as % overestimation vs true lumen). The IDR to achieve 300 HU at each VMI level was then calculated and compared with stenosis grading accuracy to establish a general rule for CM injection protocols. Plaque blooming artifacts and intraluminal iodine attenuation decreased with increasing keV. Fixed windowing (representing absolute worst case) resulted in stenosis overestimation from 77% ± 4% at 45 keV to 5% ± 2% at 190 keV, whereas optimized windowing resulted in overestimation from 29% ± 3% at 45 keV to 4% ± 1% at 190 keV. The required IDR to achieve 300 HU showed a strong linear correlation to VMI energy (R2 = 0.98). Comparison of this linear plot versus stenosis grading error and blooming artifact demonstrated that multipliers of 1, 2, and 3 times the reference IDR for theoretical clinical regimes of no, moderate, and severe calcification density, respectively, can be proposed as a general rule. This study provides a proof-of-concept in an anthropomorphic phantom for a simple pragmatic adaptation of CM injection protocols in coronary CT angiography with PCD-CT. The 1-2-3 rule demonstrates the potential for reducing the effects of calcium blooming artifacts on overall image quality.

Hotel booking intentions in the TikTok era: the role of online celebrity brand equity

Purpose This study aims to explore the pathway of increasing hotel booking intentions by mapping the linkage mechanism between the antecedents and components of brand equity to ultimately drive followers’ hotel booking intention. In addition, the role of over-endorsement as a moderating variable is also evaluated. Design/methodology/approach The conceptual model and research hypotheses were each assessed using covariance-based structural equation modeling. Paper-based and online surveys were used to collect data from 443 respondents who are TikTok users and follow at least one TikTok online celebrity, while that online celebrity must have reviewed at least one type of accommodation. Findings Except for the relationship between virtual interactivity and online celebrity brand image, the results confirmed the relationships between research concepts. Research limitations/implications Further studies are needed to validate the results in other cultural contexts, generalize findings and broaden the range of target respondents. Originality/value This study contributes to the hotel literature by illustrating how online celebrity brand equity (OCBE) drives hotel booking intentions. The study highlights the importance of antecedent factors – follower-centered drivers (e.g. lifestyle congruence, friendship) and online celebrity-led drivers (e.g. virtual interactivity, expertise) – to achieve a hierarchical relationship between OCBE components and followers’ booking intentions.

Overmodulation and phase correction of virtual images propagated by holographic curved waveguide for near-eye display

Generally, current type of waveguide used for near-eye displays is planar waveguide, which belongs to flat panel display. Compared to display system in three-dimensional space, flat panel display limits people's view of the 3-D world and is not conducive to the integration of virtual and reality. This paper proposes a holographic curved waveguide system for near-eye display. In order to analyze the propagation process of light beam in waveguide, an iterative algorithm is established based on angular spectrum theory to get the intensity distribution from each total internal reflection point. According to the simulation results and experimental phenomenon, we have developed phase compensation measures for overmodulation during beam propagation in the waveguide. The research shows that using curved waveguide can achieve beam transmission with less aberration after introducing an appropriate phase compensation in a distance, and it can also achieve beam transmission with lossless energy within a large radius range. Experiments have proven that the final coupling effect is basically consistent with the simulation results, this means that our proposal about curved waveguide has potential application value in near-eye display systems.

Optimization of photon counting CT for cardiac imaging in patients with left ventricular assist devices: An in-depth assessment of metal artifacts.

Photon counting CT (PCCT) holds promise for mitigating metal artifacts and can produce virtual mono-energetic images (VMI), while maintaining temporal resolution, making it a valuable tool for characterizing the heart. This study aimed to evaluate and optimize PCCT for cardiac imaging in patients during left ventricular assistance device (LVAD) therapy by conducting an in-depth objective assessment of metal artifacts and visual grading. Various scan and reconstruction settings were tested on a phantom and further evaluated on a patient acquisition to identify the optimal protocol settings. The phantom comprised an empty thoracic cavity, supplemented with heart and lungs from a cadaveric lamb. The heart was implanted with an LVAD (HeartMate 3) and iodine contrast. Scans were performed on a PCCT (NAEOTOM Alpha, Siemens Healthcare). Metal artifacts were assessed by three objective methods: Hounsfield units (HU)/SD measurements (DiffHU and SDARTIFACT), Fourier analysis (AmplitudeLowFreq), and depicted LVAD volume in the images (BloomVol). Radiologists graded metal artifacts and the diagnostic interpretability in the LVAD lumen, cardiac tissue, lung tissue, and spinal cord using a 5-point rating scale. Regression and correlation analysis were conducted to determine the assessment method most closely associated with acquisition and reconstruction parameters, as well as the objective method demonstrating the highest correlation with visual grading. Due to blooming artifacts, the LVAD volume fluctuated between 27.0 and 92.7 cm3. This variance was primarily influenced by kVp, kernel, keV, and iMAR (R2=0.989). Radiologists favored pacemaker iMAR, 3mm slice thickness, and T3D keV and kernel Bv56f for minimal metal artifacts in cardiac tissue assessment, and 110keV and Qr40f for lung tissue interpretation. The model adequacy for DiffHU SDARTIFACT, AmplitueLowFreq, and BloomVol was 0.28, 0.76, 0.29, and 0.99 respectively for phantom data, and 0.95, 0.98, 1.00, and 0.99 for in-vivo data. For in-vivo data, the correlation between visual grading (VGSUM) and DiffHU SDARTIFACT, AmplitueLowFreq, and BloomVol was -0.16, -0.01, -0.48, and -0.40 respectively. We found that optimal scan settings for LVAD imaging involved using 120 kVp and IQ level 80. Employing T3D with pacemaker iMAR, the sharpest allowed vascular kernel (Bv56f), and VMI at 110keV with kernel Qr40 yields images suitable for cardiac imaging during LVAD-therapy. Volumetric measurements of the LVAD for determination of the extent of blooming artifacts was shown to be the best objective method to assess metal artifacts.

Monash Rocks

This paper describes the development of the “Monash Rocks” app - designed to bring our landscape to life through augmented reality. We describe the highs and lows of the development process, the lessons we learned along the way, and our plans for further development of the app to showcase the Monash Earth Sciences Garden and extend the space into further innovative, immersive teaching and learning experiences. The creation of Monash University’s Earth Sciences Garden (MESG), a "living" geological map of Victoria collating nearly 500 rock specimens, gave us the perfect vehicle for an Augmented Reality (AR) experience. Students and visitors to the MESG can now use the Monash Rocks App on their phones to view a 3D display that overlays the live camera feed on the device enhancing the experience of the environment, taking it to another dimension. The value in augmenting a learning environment is in its ability to pull virtual objects into real scenes (Green & Chandler, 2014, p.549), in this case expanding the physical environment through time and space on a journey back millions of years. The rock now becomes alive, telling its story and supplying information that is missing in the “real life” walk through the garden.

AUGMENTED REALITY TECHNOLOGY FOR VISUALIZING DIPANEGARA UNIVERSITY BUILDINGS

Multimedia technology continues to advance, one of which is Augmented Reality (AR) technology, commonly known as the technology for merging virtual objects into the real world. Building brochures, which only display building photos and are visible from only one side, require us to visit the building to view its structure. Therefore, an idea emerged for a design of an application that uses Android-based Augmented Reality technology. This application allows users to view a more realistic physical shape of the building without visiting it directly by directing the camera towards a marker displaying the building's logo and showing a 3D model of the Dipanegara University building. It also provides general information about the building. This application is designed using 3DS Max, Unity, and Vuforia SDK, making it easier for prospective students to view the building's layout. Keywords : 3DS Max, Android, Augmented Reality, Unity, Visualization.

Buying and selling activity of online game accounts containing virtual goods that are sold on an online marketplace

With so many online game players today, various problems arise. There are so many online game players today who carry out buying and selling activities on online game accounts containing virtual objects that are widely available in various marketplaces in Indonesia. However, in these activities, the buyer often suffers losses such as the account being hacked or re-accessed by the seller. For this reason, it is necessary to have the validity of buying and selling online game accounts containing virtual objects, and how to protect the law against the buyer who purchases an account containing virtual objects. This writing uses a normative juridical approach, namely by reviewing the provisions in the Civil Code regarding the validity of buying and selling and most importantly the Law No. 19 of 2016 regarding buying and selling in electronic systems, to then be analyzed descriptively qualitatively, namely by first providing a detailed description and analysis , systematic, and comprehensive regarding the laws and regulations, norms in various countries and legal theories which are then applied to the problems studied. The results of the study show that firstly, the activity of buying and selling online game accounts which contain virtual objects based on the Law No. 19 of 2016 is legal if the organizer does not prohibit the existence of buying and selling activities by third parties. Second, legal protection for buyers who purchase online game accounts containing virtual objects based on Article 30 of the Law No. 19 of 2016 is that the seller is prohibited from re-accessing accounts that have been sold, while based on Article 49 paragraph (3) Regulation No. 71 Of 2019 the buyer has the right to get a return of goods and money if there is a difference between the goods purchased and the goods received.

Simultaneous deep ultraviolet transmission and scattering microscopy for virtual histology.

In recent years, the emergence of a variety of novel optical microscopy techniques has enabled the generation of virtual optical stains of unlabeled tissue specimens, which have the potential to transform existing clinical histopathology workflows. In this work, we present a simultaneous deep ultraviolet transmission and scattering microscopy system that can produce virtual histology images that show concordance to conventional gold-standard histological processing techniques. The results of this work demonstrate the system's diagnostic potential for characterizing unlabeled thin tissue sections and streamlining histological workflows.

A clinical-radiomics nomogram based on dual-layer spectral detector CT to predict cancer stage in pancreatic ductal adenocarcinoma

BackgroundThis study aimed to evaluate the efficacy of radiomics signatures derived from polyenergetic images (PEIs) and virtual monoenergetic images (VMIs) obtained through dual-layer spectral detector CT (DLCT). Moreover, it sought to develop a clinical-radiomics nomogram based on DLCT for predicting cancer stage (early stage: stage I-II, advanced stage: stage III-IV) in pancreatic ductal adenocarcinoma (PDAC).MethodsA total of 173 patients histopathologically diagnosed with PDAC and who underwent contrast-enhanced DLCT were enrolled in this study. Among them, 49 were in the early stage, and 124 were in the advanced stage. Patients were randomly categorized into training (n = 122) and test (n = 51) cohorts at a 7:3 ratio. Radiomics features were extracted from PEIs and 40-keV VMIs were reconstructed at both arterial and portal venous phases. Radiomics signatures were constructed based on both PEIs and 40-keV VMIs. A radiomics nomogram was developed by integrating the 40-keV VMI-based radiomics signature with selected clinical predictors. The performance of the nomogram was assessed using receiver operating characteristic (ROC) curves, calibration curves, and decision curves analysis (DCA).ResultsThe PEI-based radiomics signature demonstrated satisfactory diagnostic efficacy, with the areas under the ROC curves (AUCs) of 0.92 in both the training and test cohorts. The optimal radiomics signature was based on 40-keV VMIs, with AUCs of 0.96 and 0.94 in the training and test cohorts. The nomogram, which integrated a 40-keV VMI-based radiomics signature with two clinical parameters (tumour diameter and normalized iodine density at the portal venous phase), demonstrated promising calibration and discrimination in both the training and test cohorts (0.97 and 0.91, respectively). DCA indicated that the clinical-radiomics nomogram provided the most significant clinical benefit.ConclusionsThe radiomics signature derived from 40-keV VMI and the clinical-radiomics nomogram based on DLCT both exhibited exceptional performance in distinguishing early from advanced stages in PDAC, aiding clinical decision-making for patients with this condition.

Pixel-by-pixel correction of beam hardening artifacts by bowtie filter in fan-beam CT

Objective. Beam hardening (BH) artifacts in computed tomography (CT) images originate from the polychromatic nature of x-ray photons. In a CT system with a bowtie filter, residual BH artifacts remain when polynomial fits are used. These artifacts lead to worse visuals, reduced contrast, and inaccurate CT numbers. This work proposes a pixel-by-pixel correction (PPC) method to reduce the residual BH artifacts caused by a bowtie filter. Approach. The energy spectrum for each pixel at the detector after the photons pass through the bowtie filter was calculated. Then, the spectrum was filtered through a series of water slabs with different thicknesses. The polychromatic projection corresponding to the thickness of the water slab for each detector pixel could be obtained. Next, we carried out a water slab experiment with a mono energy E = 69 keV to get the monochromatic projection. The polychromatic and monochromatic projections were then fitted with a 2nd-order polynomial. The proposed method was evaluated on digital phantoms in a virtual CT system and phantoms in a real CT machine. Main results. In the case of a virtual CT system, the standard deviation of the line profile was reduced by 23.8%, 37.3%, and 14.3%, respectively, in the water phantom with different shapes. The difference of the linear attenuation coefficients (LAC) in the central and peripheral areas of an image was reduced from 0.010 to 0.003 cm−1 and 0.007 cm−1 to 0 in the biological tissue phantom and human phantom, respectively. The method was also validated using CT projection data obtained from Activion16 (Canon Medical Systems, Japan). The difference in the LAC in the central and peripheral areas can be reduced by a factor of two. Significance. The proposed PPC method can successfully remove the cupping artifacts in both virtual and authentic CT images. The scanned object’s shapes and materials do not affect the technique.

The perceptual effect of forms used on walls and furnishings in cafés

PurposeThis study researched the effects on the perceptual evaluations of participants for the physical environmental factors of cafés using curvilinear, rectilinear, and mixed forms to provide for the spatial states of belonging, to increase the pleasures, and to extend the periods of remaining in the space.Design/methodology/approachThis study used virtual reality (VR) technology to model the cafés designed by using curvilinear, rectilinear and mixed forms as an experimental environment. After experiencing the virtual images of the experimental spaces, participants filled out a “spatial perception” questionnaire. Perceptual evaluations of 415 participants regarding the environmental factors of cafés designed using curvilinear, linear and mixed forms were analyzed in a computer environment.FindingsAccording to the analysis of the questionnaire data, the cafés using mixed forms were perceived as more positive for the factors of appeal (inviting, restful, warm and sincere), planning (well-planned) and space freedom (roomy, uncluttered, uncrowded, large, wide and free space) compared with the cafés using curvilinear and rectilinear forms. Furthermore, the cafés using curvilinear forms were perceived as more positive for all elements compared with the cafés using rectilinear forms. However, there was a more negative approach in the perceptual evaluations of participants connected to increases in level of education.Originality/valueThe research results clearly demonstrated that the different interior and furniture forms frequently encountered in cafés cause significant effects on users’ perceptual evaluations.

Tangible and Mid-Air Interactions in Hand-Held Augmented Reality for Upper Limb Rehabilitation: An Evaluation of User Experience and Motor Performance

Hand-held augmented reality (AR) offers accessible, interactive rehabilitation options for patients with upper limb motor deficits. Incorporating hand-involved interactions (e.g., tangible and mid-air interactions) into hand-held AR provides patients with intuitive manners to perform rehabilitation exercises mimicking real-world activities. Previous work has shown the importance of user experience and motor performance in rehabilitation systems, but little was known in the literature regarding the impact of hand-involved interactions in hand-held AR on user experience and motor performance in rehabilitation exercises. Hence, this study aims to evaluate user experience and motor performance when using three types of hand-involved interactions in hand-held AR rehabilitation: (1) tangible cube (i.e., a space-multiplexed tangible interaction with a physical cube acting as a real proxy to manipulate a virtual object in the same form); (2) tangible controller (i.e., a time-multiplexed tangible interaction with a physical controller applied to manipulate a virtual object); and (3) hand motion (i.e., a form of mid-air interaction to move a virtual object with hands). Based on the findings from self-report, electroencephalography (EEG), and performance measures, this study reveals the advantages of the tangible cube over the tangible controller, both superior to the hand motion in hand-held AR rehabilitation regarding user experience and motor performance. This study offers new understanding of the advantages and disadvantages of various interaction techniques in hand-held AR rehabilitation, emphasizing crucial design considerations for these systems, with a focus on user experience and motor performance in upper limb rehabilitation.

, virtual reality embodying philosophical and conceptual heritage

ABSTRACT In this paper, we introduce the <Sunghaksipdo VR> project, which is based on Sunghaksipdo (聖學十圖). Known as the Ten Diagrams on Sage Learning, Sunghaksipdo was a heritage created by Toegye, the Korean Confucian scholar of the Joseon Dynasty. While conveying philosophical concepts such as Li (理) and Gyung (敬) and their spiritual values of mindfulness from the heritage to VR, we have focused on reconnecting the original visual diagrams and texts into perceivable VR experiences. We approached this task through the following: (1) by constructing conceptual and philosophical VR space and environments based on the original diagrams, (2) by creating conceptual objects inside VR, and (3) by designing diverse user interactions with such virtual conceptual objects. Particularly the interactions allow the user’s embodied experience and performative engagement, which become a way of understanding the meaning of the philosophical message. While explaining these with diverse exemplary cases, we hope to show how new media and interactive VR technologies can be used to realize philosophical concepts and spiritual value. Through this, we hope to discuss how VR could be imagined as a tangible philosophy discovering the plane of immanence.

Tomographic waveguide-based augmented reality display

A tomographic waveguide-based augmented reality display technique is proposed for near-eye three-dimensional (3D) display with accurate depth reconstructions. A pair of tunable lenses with complementary focuses is utilized to project tomographic virtual 3D images while maintaining the correct perception of the real scene. This approach reconstructs virtual 3D images with physical depth cues, thereby addressing the vergence-accommodation conflict inherent in waveguide augmented reality systems. A prototype has been constructed and optical experiments have been conducted, demonstrating the system’s capability in delivering high-quality 3D scenes for waveguide-based augmented reality display.

Spectral CT in the evaluation of perineural invasion status in rectal cancer.

To investigate whether preoperative spectral CT quantitative parameters can assess perineural invasion (PNI) status in rectal cancer. Sixty-two patients diagnosed with rectal cancer who underwent preoperative spectral CT were retrospectively enrolled and divided into positive and negative PNI groups according to histopathologic results. The CT attenuation value (HU) of virtual monochromatic images (40-70keV), spectral curve slope (K(HU)), effective atomic number (Zeff), and iodine concentration (IC) from spectral CT were compared between these two groups using t test or rank sum test. A nomogram was established by incorporating the independent predictors to assess the overall diagnostic efficacy. The area under the ROC curves (AUCs) were compared using the DeLong test. The preoperative spectral CT parameters (40-70keV attenuation, K(HU), Zeff, and IC) were significantly higher in the PNI-positive group compared to the PNI-negative group (all p < 0.05). The highest predictive efficiency of PNI was observed at 40keV attenuation, with an area under the curve (AUC), sensitivity, specificity, and accuracy of 0.847, 81.8%, 72.5%, and 75.8%, respectively. Binary logistic regression demonstrated that the clinical feature (cN stage) and 40keV attenuation were independent predictors of PNI status. The nomogram incorporating these two predictors (cN stage and 40keV attenuation) exhibited the best evaluation efficacy, with an AUC, sensitivity, specificity, and accuracy of 0.885, 86.4%, 77.5%, and 80.6%. Spectral CT quantitative parameters proved valuable in the preoperative assessment of PNI status in rectal cancer patients. The combination of spectral CT parameters and clinical features could further enhance the diagnostic efficiency.

Displacement prediction of inclined existing buildings with a raft foundation restored by compaction grouting in clay

Compaction grouting technique is often used to lift and rehabilitate any settled or tilted existing buildings. Prediction of building displacement prior to the grouting operation is crucial for safe remediation. However, the renovation of settled buildings using compaction grouting technique is generally empirical. In this study, we aim to propose a theoretical model to obtain the displacements of the inclined existing building with a raft foundation restored by compaction grouting in clay. The displacements of model involve two parts, (i) the ground heave displacements caused by compaction grouting, and (ii) the surface settlements resulting from a raft foundation. We estimate the displacements of the part (i) and part (ii) by means of a virtual image technique and the integration of the Boussinesqʼs displacement solutions, respectively. When the stiffness of the raft foundation is not ignored, we combine the solutions of the model with a numerical calculation method considering the interactions between soil and foundation to obtain the displacements of building. Two days of data from a engineering case are used to verify the rationality of the model. Results show that the computed displacements and the monitored displacements are in good agreement. The maximum and minimum deviations between the computed displacements and the monitored displacements are 22.3 % (monitored point S14) and 1.3 % (monitored point S5), respectively. Overall, the proposed model can be used to predict the displacements of inclined existing buildings with a raft foundation restored by compaction grouting in clay, as well as optimize the design of building rehabilitation work.

Tracking and co-location of global point clouds for large-area indoor environments

Extended reality (XR) experiences are on the verge of becoming widely adopted in diverse application domains. An essential part of the technology is accurate tracking and localization of the headset to create an immersive experience. A subset of the applications require perfect co-location between the real and the virtual world, where virtual objects are aligned with real-world counterparts. Current headsets support co-location for small areas, but suffer from drift when scaling up to larger ones such as buildings or factories. This paper proposes tools and solutions for this challenge by splitting up the simultaneous localization and mapping (SLAM) into separate mapping and localization stages. In the pre-processing stage, a feature map is built for the entire tracking area. A global optimizer is applied to correct the deformations caused by drift, guided by a sparse set of ground truth markers in the point cloud of a laser scan. Optionally, further refinement is applied by matching features between the ground truth keyframe images and their rendered-out SLAM estimates of the point cloud. In the second, real-time stage, the rectified feature map is used to perform localization and sensor fusion between the global tracking and the headset. The results show that the approach achieves robust co-location between the virtual and the real 3D environment for large and complex tracking environments.

Added value of 40 keV virtual monoenergetic images for diagnosing malignant pleural effusion on chest CT.

This study aimed to evaluate the added value of 40 keV virtual mono-energetic images (VMIs) obtained from dual-layer detector CT (DLCT) for diagnosing malignant pleural effusion (MPE) in patients presenting with unilateral pleural effusion on chest CT. This retrospective study included 75 patients with unilateral pleural effusion who underwent contrast-enhanced chest CT scans using DLCT. Quantitative and qualitative assessments of the visibility of pleural thickening were conducted on both conventional 120 kVp images and 40 keV VMIs. Two independent radiologists reviewed chest CT scans with or without 40 keV VMIs to detect pleural nodules or nodular thickening for the diagnosis of MPE. Diagnostic performances were compared and independent predictors of MPE were identified through multivariate logistic regression analysis using CT and clinicopathologic findings. Pleural thickening associated with MPE demonstrated a higher contrast-to-noise ratio value and greater visual conspicuity in 40 keV VMIs compared to benign effusions (p < 0.05). For both readers, the use of 40 keV VMIs significantly improved (p < 0.05) the diagnostic performance in terms of sensitivity and area under the curve (AUC) for diagnosing MPE through the detection of pleural nodularity. Inter-observer agreements between the two readers were substantial for both 120 kVp images alone and the combined use of 40 keV VMIs. Initial cytology results and pleural nodularity at 40keV were identified as independent predictors of MPE. The use of 40 keV VMIs from DLCT can improve diagnostic performance of readers in detecting MPE among patients with unilateral pleural effusion.

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.

Variation in Hounsfield unit calculated using dual-energy computed tomography: comparison of dual-layer, dual-source, and fast kilovoltage switching technique.

The purpose of the study is to investigate the variation in Hounsfield unit (HU) values calculated using dual-energy computed tomography (DECT) scanners. A tissue characterization phantom inserting 16 reference materials were scanned three times using DECT scanners [dual-layer CT (DLCT), dual-source CT (DSCT), and fast kilovoltage switching CT (FKSCT)] changing scanning conditions. The single-energy CT images (120 or 140 kVp), and virtual monochromatic images at 70keV (VMI70) and 140keV (VMI140) were reconstructed, and the HU values of each reference material were measured. The difference in HU values was larger when the phantom was scanned using the half dose with wrapping with rubber (strong beam-hardening effect) compared with the full dose without the rubber (reference condition), and the difference was larger as the electron density increased. For SECT, the difference in HU values against the reference condition measured by the DSCT (3.2 ± 5.0 HU) was significantly smaller (p < 0.05) than that using DLCT with 120 kVp (22.4 ± 23.8 HU), DLCT with 140 kVp (11.4 ± 12.8 HU), and FKSCT (13.4 ± 14.3 HU). The respective difference in HU values in the VMI70 and VMI140 measured using the DSCT (10.8 ± 17.1 and 3.5 ± 4.1 HU) and FKSCT (11.5 ± 21.8 and 5.5 ± 10.4 HU) were significantly smaller than those measured using the DLCT120 (23.1 ± 27.5 and 12.4 ± 9.4 HU) and DLCT140 (22.3 ± 28.6 and 13.1 ± 11.4 HU). The HU values and the susceptibility to beam-hardening effects varied widely depending on the DECT scanners.