3D Distortion Research Articles

Influences in Experimental Studies on the Characteristics of Transonic Shock Buffet

This article examines the evolution of transonic shock buffet on the OAT15A supercritial airfoil, aspiring to elucidate some of the causes of disparate buffet-relevant settings reported in the literature. Experimental campaigns on three distinct chord lengths are conducted thus resulting in chord Reynolds numbers of 1.3×106, 2.0×106, and 2.7×106. Continuous variations in Mach and AoA allow mapping the shock wave behavior across a large parameter space and capturing the transition between prebuffet, onset, developed buffet, and offset. High-speed focusing schlieren imaging is employed to extract the temporal and spectral nature of buffet and to deduce key quantities that characterize the unsteadiness. Three-dimensional effects along the span due to interference with the side walls are assessed thoroughly, revealing that phases of upstream shock motion and large separation are accompanied by 3D distortion. Even though this effect gains relevance at reduced aspect ratio, a substantially 2D character of the shock surface around the centerplane is confirmed. Fully developed buffet governed by a 2D buffet mode is proven to exist across all test cases, although the buffet peak condition is gradually shifted toward reduced angle of attack, yet greater Mach number with increased Reynolds number. Conversely, accompanied by severely increased angles of attack, the buffet mechanism appears more volatile for small chord length and is consolidated with enlarged chord, which strongly suggests a dependence on the state of the turbulent boundary layer.

The influence of welding-induced 3D residual stress and distortion on the ultimate strength of multi-stiffened thin plate structures under cyclic load

Stiffened thin plates made of high-strength steel are widely employed in ship hull structures. Their strength capacity is highly sensitive to the welding imperfections and potential extreme cyclic loading from harsh sea state. In this work, a thermal elasto-plastic finite element analysis is conducted to simulate the 3D distribution of welding-induced residual stress and distortion of stiffened thin plate structures with triple spans and triple bays varying the plate thickness and heat input. Experimental results provided by other scholars are used to validate the welding simulation. Afterwards, the ultimate strength and collapse behaviour of the welded structures under different load patterns are dealt with, including monotonic compression load, cyclic compression-tension load and cyclic compression load. Observation from numerical results indicates that, in general, the compressive strength is reduced in each considered cycle by the residual stress as the amplitude of cyclic compression-tension load approximates to the ultimate compressive strain. When this parameter is much greater than the ultimate compressive strain or the stiffened plate is subjected to cyclic compression load, the reduction in ultimate strength is significant in the first cycle, whereas the reduction is ignorable in the later cycles. Besides, if the buckling mode of initial deflection with antisymmetric configuration is superposed to the symmetric out-of-plane welding distortion, impact of the residual stress will be diminished as the asymmetry becomes notable.

Imaging extended single crystal lattice distortion fields with multi-peak Bragg ptychography

Recent advances in phase-retrieval-based x-ray imaging methods have demonstrated the ability to reconstruct 3D distortion vector fields within a nanocrystal by using coherent diffraction information from multiple crystal Bragg reflections. However, these works do not provide a solution to the challenges encountered in imaging lattice distortions in crystals with significant defect content that result in phase wrapping. Moreover, these methods only apply to isolated crystals smaller than the x-ray illumination, and therefore cannot be used for imaging of distortions in extended crystals. We introduce multi-peak Bragg ptychography which addresses both challenges via an optimization framework that combines stochastic gradient descent and phase unwrapping methods for robust image reconstruction of lattice distortions and defects in extended crystals. Our work uses modern automatic differentiation toolsets so that the method is easy to extend to other settings and easy to implement in high-performance computers. This work is particularly timely given the broad interest in using the increased coherent flux in fourth-generation synchrotrons for innovative material research.

Influence of wind directionality on the three-dimensional distortion of buffeting force on a streamlined bridge deck: Insight into the pylon interference effect

The present work aims to experimentally investigate the influence of wind directionality on the three-dimensionality of buffeting force on a streamlined bridge deck, considering the pylon interference effect (PIE). The pylon has an obvious impact on the downstream flow structure under the skew wind, influencing the aerodynamic loads acting on the bridge deck. The results show that the most dangerous wind direction exists at 30° for the downstream bridge deck, indicating the invalidation of the traditional “cosine rule.” It indicates that the lift force will be amplified due to the PIE, depending on the yaw angle of the oncoming flow. When turbulence passes through the pylon, the large-scale eddies in the wake region will be broken into small-scale eddies, attenuating the integral length scale in comparison with that of the free-stream turbulence. Consequently, the lift spectrum and corresponding three-dimensional aerodynamic admittance (AAF) increase in the high-frequency domain, resulting in the decrease in the spanwise correlation under the skew wind. Notably, the two-dimensional (2D) AAF indicates that the 2D distortion effect of turbulence on the lift increases in the wake region, causing the 2D AAF to decay rapidly in the high-frequency domain.

Commissioning and implementing a Quality Assurance program for dedicated radiation oncology MRI scanners.

ACR and AAPM task group's guidelines addressing commissioning for dedicated MR simulators were recently published. The goal of the current paper is to present the authors' 2-year experience regarding the commissioning and introduction of a QA program based on these guidelines and an associated automated workflow. All mandatory commissioning tests suggested by AAPM report 284 were performed and results are reported for two MRI scanners (MAGNETOM Sola and Aera). Visual inspection, vendor clinical or service platform, third-party software, or in-house python-based code were used. Automated QA and data analysis was performed via vendor, in-house or third-party software. QATrack+ was used for QA data logging and storage. 3D geometric distortion, B0 inhomogeneity, EPI, and parallel imaging performance were evaluated. Contrasting with AAPM report 284 recommendations, homogeneity and RF tests were performed monthly. The QA program allowed us to detect major failures over time (shimming, gradient calibration and RF interference). Automated QA, data analysis, and logging allowed fast ACR analysis daily and monthly QA to be performed in 3h. On the Sola, the average distortion is 1mm for imaging radii of 250mm or less. For radii of up to 200mm, the maximum, average (standard deviation) distortion is 1.2 and 0.4mm (0.3mm). Aera values are roughly double the Sola for radii up to 200mm. EPI geometric distortion, ghosting ratio, and long-term stability were found to be under the maximum recommended values. Parallel imaging SNR ratio was stable and close to the theoretical value (ideal g-factor). No major failures were detected during commissioning. An automated workflow and enhanced QA program allowed to automatically track machine and environmental changes over time and to detect periodic failures and errors that might otherwise have gone unnoticed. The Sola is more geometrically accurate, with a more homogenous B0 field than the Aera.

Ultra-wide field and new wide field composite retinal image registration with AI-enabled pipeline and 3D distortion correction algorithm

PurposeThis study aimed to compare a new Artificial Intelligence (AI) method to conventional mathematical warping in accurately overlaying peripheral retinal vessels from two different imaging devices: confocal scanning laser ophthalmoscope (cSLO) wide-field images and SLO ultra-wide field images.MethodsImages were captured using the Heidelberg Spectralis 55-degree field-of-view and Optos ultra-wide field. The conventional mathematical warping was performed using Random Sample Consensus—Sample and Consensus sets (RANSAC-SC). This was compared to an AI alignment algorithm based on a one-way forward registration procedure consisting of full Convolutional Neural Networks (CNNs) with Outlier Rejection (OR CNN), as well as an iterative 3D camera pose optimization process (OR CNN + Distortion Correction [DC]). Images were provided in a checkerboard pattern, and peripheral vessels were graded in four quadrants based on alignment to the adjacent box.ResultsA total of 660 boxes were analysed from 55 eyes. Dice scores were compared between the three methods (RANSAC-SC/OR CNN/OR CNN + DC): 0.3341/0.4665/4784 for fold 1-2 and 0.3315/0.4494/4596 for fold 2-1 in composite images. The images composed using the OR CNN + DC have a median rating of 4 (out of 5) versus 2 using RANSAC-SC. The odds of getting a higher grading level are 4.8 times higher using our OR CNN + DC than RANSAC-SC (p < 0.0001).ConclusionPeripheral retinal vessel alignment performed better using our AI algorithm than RANSAC-SC. This may help improve co-localizing retinal anatomy and pathology with our algorithm.

Multi-modal fusion architecture search for camera-based semantic scene completion

Camera-based Semantic scene completion (SSC) aims to infer the 3D volumetric occupancy and semantic categories of a scene simultaneously from a single RGB image. The main challenge of camera-based SSC is the lack of geometry information compared with RGB-D SSC. Although the estimated depth from RGB image will help SSC to some extent, the depth prediction quality is far from the demand of SSC. To solve this problem, we propose a NAS-based multi-modal fusion method to incorporate the semantic and geometry information from other intermediate representations (predicted depth and predicted 2D segmentation) to form a more robust 2D feature representation. A key idea of this design is that explicit 2D semantic information could alleviate the misleading information of 3D distortions introduced by estimated depth. Specifically, we propose the Confidence-Block to automatically learn an optimal architecture for routing and obtaining the depth prediction confidence. We propose the two-level fusion search space by decomposing the fusion search space into fusion stage search space and fusion operation search space. Moreover, we propose a confidence-aware 2D–3D projection module to alleviate the 3D projection error. Extensive experiments show that our method outperforms the state-of-the-art method by a large margin using a single RGB image on NYU and NYUCAD datasets.

ACCURATE REGISTRATION BETWEEN ULTRA-WIDE-FIELD AND NARROW ANGLE RETINA IMAGES WITH 3D EYEBALL SHAPE OPTIMIZATION.

The Ultra-Wide-Field (UWF) retina images have attracted wide attentions in recent years in the study of retina. However, accurate registration between the UWF images and the other types of retina images could be challenging due to the distortion in the peripheral areas of an UWF image, which a 2D warping can not handle. In this paper, we propose a novel 3D distortion correction method which sets up a 3D projection model and optimizes a dense 3D retina mesh to correct the distortion in the UWF image. The corrected UWF image can then be accurately aligned to the target image using 2D alignment methods. The experimental results show that our proposed method outperforms the state-of-the-art method by 30%.

MRI sequence optimisation methods to identify cranial nerve course for radiotherapy planning.

Magnetic resonance imaging (MRI) is being increasingly used to improve radiation therapy planning by allowing visualisation of organs at risk that cannot be well-defined on computed tomography (CT). Diagnostic sequences are increasingly being adapted for radiation therapy planning, such as the use of heavily T2-weighted 3D SPACE (Sampling Perfection with Application optimised Contrasts using different flip angle Evolution) sequence for cranial nerve identification in head and neck tumour treatment planning. A 3D isotropic T2 SPACE sequence used for cranial nerve identification was adapted for radiation therapy purposes. Distortion was minimised using a spin-echo-based sequence, 3D distortion correction, isocentre scanning and an increased readout bandwidth. Radiation therapy positioning was accounted for by utilising two small flex, 4-channel coils. The protocol was validated for cranial nerve identification in clinical applications and distortion minimisation using an MRI QA phantom. Normal anatomy of the cranial nerves CI-CIX, were presented, along with a selection of clinical applications and abnormal anatomy. The usefulness of cranial nerve identification is discussed for several case studies, particularly in proximity to tumours extending into the base of skull region. In-house testing validated that higher bandwidths of 600 Hz resulted in minimal displacement well below 1 mm. The use of MRI for radiation therapy planning allows for greater individualisation and prediction of patient outcomes. Dose reduction to cranial nerves can decrease late side effects such as cranial neuropathy. In addition to current applications, future directions include further applications of this technology for radiation therapy treatments.

The Efficacy of Trunk Bracing With an Instrumented Corrective Exercise on Spinal Deformity, Pulmonary Function, Trunk Muscle Endurance, and Quality of Life in Adolescent Idiopathic Scoliosis: Protocol for a Parallel Groups Clinical Study.

Adolescent idiopathic scoliosis is a 3D spine distortion with an unidentified etiology. It results in noticeable trunk deformity, decreased muscle strength and endurance at the trunk, changes in chest volume, breathing issues, and ultimately a decline in the quality of life. Trunk bracing and corrective exercises make up most of the treatment of patients with scoliosis when their deformity is between 20° and 45°, and they have not yet attained skeletal maturity. Evidence suggests that spinal deformity in people with scoliosis may result from improper motor control. Automatic response training is an exercise therapy technique that can modify the pattern of trunk muscle control for supporting the spinal column in normal alignment. An apparatus called a cantilever device is required for this type of exercise, which facilitates training at home. In spite of research showing the benefit of braces and therapeutic exercise in adolescents with scoliosis, less emphasis has been given to the impact of home-based training, especially when this intervention is paired with braces. We aim to compare the efficacy of bracing and a conventional exercise program to a combination treatment that includes trunk bracing and exercises with a cantilever device performed at home on the degree of spine curvature, pulmonary function, trunk muscular endurance, and quality of life. This study was a 2-arms parallel-group clinical study. A total of 16 adolescents with idiopathic scoliosis and single lumbar and thoracolumbar curves of 20°-45° were recruited and randomly assigned into 2 groups. Group A received a combination of trunk bracing and exercise using an instrument known as a "cantilever." Group B (controls) received trunk bracing and a conventional exercise program (without a tool). The study outcomes were the Cobb angle of the scoliotic curve, pulmonary function, the endurance of the trunk muscles, and quality of life. The study outcomes were measured at 2 time points: before the intervention (T1) and 12 weeks following the start of the intervention (T2; at this time, the intervention period has been completed). Multivariate analysis of variance was used to test between- and within-group differences. Recruitment for this study began in fall 2022 and is expected to be completed by the end of summer 2023. We studied the efficacy of a combined trunk bracing program and postural response exercises using a cantilever device in treating adolescent idiopathic scoliosis and compared it with trunk bracing and conventional home exercises. Exercises performed at home using a cantilever device are anticipated to raise the endurance of trunk muscles, which will help reduce trunk deformity, enhance pulmonary function, and improve the quality of life of participants. Iranian Registry of Clinical Trials IRCT20220330054371N1; https://www.irct.ir/trial/62811. PRR1-10.2196/43265.

3D spatial distortion model based on the Lagrange difference in a binocular visual system.

The accuracy of binocular visual system calibration using the traditional method is poor in the depth direction. To enlarge the high-accuracy field of view (FOV) of a binocular visual system, a 3D spatial distortion model (3DSDM) based on the 3D Lagrange difference is proposed to minimize 3D space distortion. In addition, a global binocular visual model (GBVM) is proposed that contains the 3DSDM and a binocular visual system. The GBVM calibration method and 3D reconstruction method are based on the Levenberg-Marquardt method. Experiments were carried out to verify the accuracy of our proposed method by measuring the length of the calibration gauge in a 3D space. Experiments show that compared to traditional methods our method can improve the calibration accuracy of a binocular visual system. Our GBVM has a lower reprojection error, higher accuracy, and a larger working field.

Comparison of 3D positional accuracy of implant analogs in printed resin models versus conventional stone casts: Effect of implant angulation.

To study the effect of implant angulation on 3D linear and absolute angular distortions of implant analogs in printed resin models and conventional stone casts. Three sectional master models with two implants with total inter-implant angulations of 0°, 10°, and 20° were fabricated. For each master model, five conventional stone casts (CS) and printed resin models (PM) were fabricated (n=5). Test models were made with nonsplinted impression copings and open tray polyether impressions for the CS groups and scan bodies scanned using an intraoral scanner for the PM groups. The physical positions of the implants and implant analogs were measured with a coordinate measuring machine. 3D linear distortion (ΔR) and absolute angular distortion (Absdθ) defined the 3D positional accuracy of the analogs in the test models. Univariate ANOVA was used to analyze data followed by post hoc tests (Tukey HSD, α=0.05). Mean ΔR was significantly greater for PM10 (73.5±8.9µm) and PM20 (65.5±33.3µm) compared to CS0 (16.8±14.1µm), CS10 (22.2±13.0µm), CS20 (15.6±19.9µm), and PM0 (23.9±16.1µm). For Absdθ, there were no significant differences between test groups. With conventional stone casts, implant angulation had no significant effect on 3D linear and absolute angular distortions. Amongst printed resin models test groups, angulated implants had significantly greater ΔR. Amongst angulated implants test groups, printed resin models had significantly greater ΔR than conventional stone casts. Compared to the master model, all test groups, regardless of inter-implant angulation, produced greater inter-analog distances.

Pseudo-Reference Point Cloud Quality Measurement Based on Joint 2-D and 3-D Distortion Description

Pseudo-Reference Point Cloud Quality Measurement Based on Joint 2-D and 3-D Distortion Description

Metatarsophalangeal and Metatarso-Sesamoid Joint Interaction in Hallux Valgus Deformity: A Case- Control Study

Category: Bunion; Lesser Toes; Midfoot/Forefoot Introduction/Purpose: Hallux valgus deformity (HVD) is a complex 3D distortion that involves varus, dorsiflexion and pronation of the first metatarsal. Deformity is usually assessed by conventional 2D measurements such as hallux valgus and intermetatarsal angle. Weightbearing CT (WBCT) 3D Distance Mapping (DM) and Coverage Mapping (CM) allow assessment of relative positioning between opposing articular surfaces, providing information in regards to articular coverage and joint subluxation, that can potentially influence development of arthritic degeneration and symptoms, as well as dictate outcomes. The aim of this study was to develop a DM and CM algorithm to assess metatarsophalangeal (MTP) and metatarso-sesamoid (MS) joint interaction in HVD patients and compare it to healthy controls. We hypothesized that significant MTP and MS joints lateral subluxation would be observed. Methods: In this IRB-approved study, we included 9 HVD patients (mean age 37.1y; 6F/3M) and 5 controls (mean age 39y; 4F/1M) that underwent foot WBCT foot. Bone segmentation of WBCT images for the first and second metatarsals, first and second proximal phalanxes as well as tibial and fibular sesamoids was performed using specific software. Joint interaction with DM and CM of the first and second MTP joints, as well as MS joints were calculated. The surface of the MTP joints were divided in a 2x2 grid using principal axes to provide a more detailed analysis. DMs were color coded to facilitate data interpretation (Figure). Blue color represented expected normal joint interaction (distances from 1 to 3 mm), yellow/red color symbolized increased joint distances (distances from 3 to 5 mm) and pink color indicate completely uncovered articular areas (distances &gt;5mm). Comparisons were performed with independent t-tests/Wilcoxon. P values &lt;.05 were considered significant. Results: Examples of coverage maps for an HVD patient and a control are presented in the attached Figure, demonstrating the obvious lateral and dorsal displacement of the distance maps for joint interaction of the first MTP joint, with decreased articular coverage of the medial aspect of the joint. When comparing first MTP joint articular coverage (CMs), HVD patients demonstrated significantly decreased coverage of the dorsomedial quadrant (77%, p=0.0002), and significantly increased coverage of the plantarlateral (182%, p=0.005) and dorsolateral quadrants (44.9%, p=0.035). Findings are consistent with lateral first MTP joint subluxation and dorsiflexion of the first metatarsal. The second MTP joint demonstrated findings consistent with early hammertoe dorsiflexion contracture and dorsolateral joint subluxation, with significantly decreased articular coverage of the plantarmedial quadrant (88%, p=0.01). No significant changes in joint coverage were observed for the MS joints, however a significant widening of the fibular MS joint was noticed (76.7%, p=0.013). Conclusion: In this case-control study, we developed a Distance and Coverage Map WBCT Algorithm to objectively assess 3D joint interaction, articular coverage and subluxation in HVD. We observed significant amount of first and second MTP joint subluxation in HVD patients when compared to controls, with a plantarmedial and dorsolateral direction for respectively the first and second MTP joints. No significant joint subluxation of the metatarso-sesamoid joint was noted. Our hope is that DM and CM can optimize diagnosis, staging, and assessment of treatment and outcomes in hallux valgus and lesser toe deformities. Additional prospective and appropriately sized studies are needed.

Application of visual mechanical signal detection and loading platform with super‐resolution based on deep learning

A visual mechanical signal detection and loading platform with super-resolution based on deep learning is designed to improve the detection accuracy of mechanical signals. The visual mechanical signal detection and loading platform with super-resolution include three-dimensional (3D) biological force quantitative detection platform and the mechanical signal loading platform with 3D magnetic distortion and ultrahigh resolution. In the 3D biological force quantitative detection platform, four 3D force sensors are used to collect mechanical signals, and the improved fuzzy clustering fusion method is used to fuse the mechanical signals collected by 3D force sensors to improve the detection accuracy of mechanical signals. The mechanical signal loading platform of 3D magnetic distortion and ultrahigh resolution technology connects the 3D magnetic distortion instrument and microscope, collects images through high-speed scanning components and distorted magnetic field, reconstructs the collected images by deep learning method, obtains ultrahigh-resolution mechanical signal visual images, and triggers mechanical signal loading and release by synchronous interactive system. The consequences of the experiment demonstrate that the designed platform can display the super-resolution mechanical signals through the visual interface. The mechanical signals are loaded in different directions, and the detection accuracy of mechanical signals is higher than 99.5%.

2D Constellation Distortion for Subduing Equalization Noise in Bandwidth- Limited IMDD Systems

Bandwidth-limited IMDD systems suffer from the noise boosted by the strong equalization at the receiver. This letter proposes a multiplication-free approach that reduces the impacts of the equalizer-enhanced colored noise through time-interleaving the received symbols and distorting the two-dimensional (2D) constellation such that the noise correlation is subdued. The 2D distortion map is predefined and retrieved from a look-up table. The proposed 2D constellation distortion is evaluated after the linear feed-forward equalizer and Volterra nonlinear equalizer. Experimental results show a BER reduction of 40% when the 2D constellation distortion is employed after the equalizer for the 135 Gbaud PAM4 and 110 Gbaud PAM6 signals. Owing to the proposed approach, we transmit a net data rate of 250 Gbps/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> PAM4 and PAM6 in the O-band over 2 km of SSMF at a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.8\times 10^{-3}$ </tex-math></inline-formula> below the 6.7% overhead HD-FEC using a 47 GHz SiP modulator, linear equalization, and the proposed 2D distortion.

＜Editors' Choice＞ Evaluation of system-related magnetic resonance imaging geometric distortion in radiation therapy treatment planning: two approaches and effectiveness of three-dimensional distortion correction.

ABSTRACTWe propose two methods to evaluate system-related distortion in magnetic resonance imaging (MRI) in radiation therapy treatment planning (RTP) and demonstrate the importance of three-dimensional (3D) distortion correction (DC) by quantitatively measuring the distortion magnitude. First, a small pin phantom was scanned at multiple positions using an external laser guide for accurate phantom placement and combined into one image encompassing a large area. Direct plane images were used for evaluating in-plane distortion and multiplanar reconstruction images for through-plane distortion with no DC, two-dimensional (2D) DC, and 3D DC. Second, a large grid sheet was scanned as the direct plane of the phantom placement. The distortion magnitude was determined by measuring the displacement between the MRI and reference coordinates. The measured distortions were compared between in- and through-plane when applying DC and between the two methods. The small pin phantom method can be used to evaluate a wide range of distortions, whereas data from the entire plane can be obtained with a single scan using the grid sheet without a laser guide. The mean distortion magnitudes differed between the methods. Furthermore, the 3D DC reduced in- and through-plane distortions. In conclusion, the small pin phantom method can be used to evaluate a wide range of distortions by creating a combined image, whereas the grid sheet method is simpler, accurate, repeatable, and does not require a special-order phantom or laser guide. As 3D DC reduces both in- and through-plane distortions, it can be used to improve RTP quality.

Three-dimensional mapping, recording and ablation in simulated and induced ventricular tachyarrhythmias during mechanical circulatory support using the percutaneous heart pump.

Due to their internal rotating magnets, conventional impeller-driven percutaneous ventricular assist devices (PVADs) yield high-frequency electrogram artifact and electromagnetic interference (EMI) when used with magnetic-based 3D electroanatomic mapping systems. The new percutaneous heart pump (PHP; Abbott, Chicago, IL) is a 14-French, 5-L/min, impeller axial-flow PVAD with a novel design that utilizes an external motor. We evaluated the feasibility of 3D mapping and radiofrequency ablation (RFA) in vivo during PHP mechanical circulatory support (MCS) in simulated ventricular tachycardia (pacing at 300ms)and ventricular flutter (VFL, pacing at 200ms) and also duringventricular fibrillation (VF) in a porcine model. Anterograde (right ventricular), transseptal, retrograde, and epicardial right and left ventricular 3D mapping (EnSite/CARTO) and RFA were performed in 6 swine using high-density mapping and force-sensing RFA catheters (TactiCath/ThermoCool). Surface and intracardiac electrograms and 3D maps were analyzed for noise/interference withandwithout MCS using PHP in sinus rhythm and simulated VT/VFL and VF. Mapping and RFA proved feasible in the presence of MCS using PHP. The mean arterial pressure in sinus rhythm was 55 ± 2mmHg (baseline) and 84 ± 4mmHg during MCS with PHP and well-maintained during simulated VT (73 ± 8mmHg) and VFL (65 ± 2mmHg) and even inVF (65 ± 5mmHg). No electrogram noise/artifact, EMI, or 3D map distortions were observed during mapping/RFA with either of twomapping systems. Endocardial and epicardial 3D mappingandRFA in the presence of PHP are feasible and offer significant MCS during simulated VT/VFL and VF. Furthermore, PHP yielded no electrogram noise/artifact, EMI, or 3D mapping distortions in conjunction with magnetic-based 3D mapping systems.

Evaluation of a Bone Coordinate System Constructed Using MR Image Composing

To evaluate the accuracy of a bone coordinate system constructed using MR image composing. A femoral coordinate system constructed using image composing of MR images of a whole bovine femur was evaluated using CT images. The MR images were acquired by moving the table and were processed with 3D distortion correction and composing. To evaluate the reproducibility of the measurements, the same operator repeated the construction of the femoral coordinate system. In addition, distortions in the MR images were evaluated in comparison with those in the CT images. The center position of the femoral coordinate system constructed using the MR image composing was 1.6±0.9 mm on the X-axis, 1.5±0.8 mm on the Y-axis, and 0.2±0.3 mm on the Z-axis, and the rotation of each axis was 1° or less. The distortion of the composed MR image was about 0.3%. The femoral coordinate system constructed using MR image composing had the same accuracy as a system constructed with CT images. The effect of MR image composing on the construction of the femoral coordinate system was small.

Modeling the mechanics of growing epithelia with a bilayer plate theory

Epithelia, which consists of cell sheets lying on a substrate, are prevalent structures of multicellular organisms. The physical basis of epithelial morphogenesis has been intensely investigated in recent years. However, as 2D mechanics focused most attention, we still lack a rigorous description of how the mechanical interactions between the cell layer and its substrate can lead to 3D distortions. This work provides a complete description of epithelial mechanics using the most straightforward model of an epithelium: a thin elastic bilayer. We first provide experimental evidence in Drosophila tissues that localized alterations of the cell substrate (the extracellular matrix) can lead to profound 3D shape changes in epithelia. We then develop an analytical model modifying the Föppl–von Kármán equation with growth for bilayers. We provide a complete description of all contributions from biophysical characteristics of epithelia. We show how any localized inhomogeneity of stiffness or thickness drastically changes the bending process when the two layers grow differently. Comparison with finite element simulations and experiments performed on Drosophila wing imaginal discs validates this approach for thin epithelia