Sector Width Research Articles

Abstract 14470: Right Ventricular Flow Visualization and Characterization via High Speed Volumetric Echo-PIV

Introduction: Although 4D echocardiography is used for many clinical applications, the evolving vortex flow in the right ventricle (RV) is relatively unknown and cannot be characterized with conventional echocardiography. An obstacle is that acquiring high frame rate (>100fps) data in presence of contrast is challenging and has not yet reported. Hypothesis: High frame-rate 4D echocardiographic data in presence of contrast can elucidate RV vortex flow via volumetric Echo-PIV (V-Echo-PIV). Methods: We devised a new transthoracic echocardiography (TTE) protocol using a Philips EPIQ CV9 ultrasound system with a 3D matrix probe (X5-1c) to acquire high frame-rate 4D data for processing with V-Echo-PIV. Apical RV focused view was used for full-volume acquisition by limiting the sector width and imaging depth solely to the entire RV. Visualization of the RV flow and wall dynamics was achieved by IV administration of Optison™ and Normal Saline. VolDICOMs were processed with V-Echo-PIV to obtain RV blood flow velocity field during the full cardiac cycle. Results: We improve the frame rates' scan lines to +30Hz. A 100Hz is achieved by stitching 4 cycles. We show that 4D RV flow can be quantified and characterized at high temporal resolution using V-Echo-PIV. Fig. 1A shows cine blood velocity in a healthy subject with a 51bpm heart rate. For which, V-Echo-PIV acquired 117 three-dimensional vector fields in one cardiac cycle, given the setting of 100Hz acquisition rate. The figure features flow patterns from systole to diastole, from left to right. Fig. 1B depicts the iso-surface of transient tricuspid vortex during diastolic RV filling. Conclusions: Enabled by high speed acquition in presence of contrast, V-Echo-PIV can be used as a viable alternative to 4D Flow MRI to visualize and evaluate real-time intra-cardiac blood flow, as it requires only a very short acquisition time and can be used wherever an echocardiography machine with matrix probes is available.

Retrospective Ultrasound Doppler Quantification Using a Single Acquisition in Healthy Adults

Using an experimental tool for retrospective ultrasound Doppler quantification-with high temporal resolution and large spatial coverage-simultaneous flow and tissue measurements were obtained. We compared and validated these experimental values against conventional measurements to determine if the experimental acquisition produced trustworthy tissue and flow velocities. We included 21 healthy volunteers. The only exclusion criterion was the presence of an irregular heartbeat. Two ultrasound examinations were performed for each participant, one using conventional and one using experimental acquisition. The experimental acquisition used multiple plane wave emissions combined with electrocardiography stitching to obtain continuous data with over 3500 frames per second. With two recordings covering a biplane apical view of the left ventricle, we retrospectively extracted selected flow and tissue velocities. Flow and tissue velocities were compared between the two acquisitions. Statistical testing showed a small but significant difference. We also exemplified the possibility of extracting spectral tissue Doppler from different sample volumes in the myocardium within the imaging sector, showing a decrease in the velocities from the base to the apex. This study demonstrates the feasibility of simultaneous, retrospective spectral and color Doppler of both tissue and flow from an experimental acquisition covering a full sector width. The measurements were significantly different between the two acquisitions but were still comparable, as the biases were small compared to clinical practice, and the two acquisitions were not done simultaneously. The experimental acquisition also enabled the study of deformation by simultaneous spectral velocity traces from all regions of the image sector.

АНАЛІЗ ЗАСТОСОВНОСТІ МЕТОДУ ДВОЧАСТОТНОЇ ІНТЕРФЕРОМЕТРІЇ ДЛЯ ВИМІРЮВАННЯ КУТА МІСЦЯ ЦІЛЕЙ У ДВОКООРДИНАТНИХ РЛС

Subject and Purpose. The study deals with the dual-frequency radio interferometry technique, which is based on the employment of two fairly close frequencies with the aim to remove ambiguity of the radar target elevation estimation using 2D-radar and eliminate 2 pm-uncertainty of the signal phase difference measurement. Analysis of random noise action on the accuracy of the elevation angle estimation by the dual-frequency radio interferometry and assessment of practical applicability of the method make up the purpose of the paper. Methods and Methodology. The noise action on the elevation angle measurement accuracy is examined through a series of an- alytical calculations with the use of statistical analysis methods. The noise in each receiving channel is modeled in terms of additive, statistically independent stationary Gaussian processes with zero mean values and equal variances. The calculation results are checked via computer simulations with statistics estimations for 106 random noise realizations. Results. A correct condition has been developed for the sector width where the target elevation angle is unambiguously estimated depending on the space separation of the antennas (baselines) and the frequency ratio. Expressions for elevation angle estimation errors have been obtained, showing that the error is mainly contributed by the faults in the determination of the ambiguity interval number. A probability of the correct determination of the ambiguity interval number has been derived depending on the signal- to-noise ratio and the frequency difference, indicating that almost one hundred per cent probability of the correct determination of the ambiguity interval number is only achieved when the signal-to-noise ratio exceeds 30 dB. A comparative analysis has been performed between the methods of dual-frequency interferometry and conventional phase-difference direction finding in the case of close X-band frequencies and the same sectors of survey. Conclusions. The dual-frequency radio interferometry technique with close frequencies has been shown to outperform the stand- ard phase-difference direction-finding method only when the signal-to-noise ratio is sufficiently high (over 30 dB). In principle, the accuracy of the technique seems possible to improve by taking significantly different frequencies selected with regard to the scale negotiation condition. However, it should be mentioned that the implementation of the relevant algorithm in practice is much more complicated than the conventional scheme with a single frequency and several antenna baselines.

Global extreme significant wave height within the dominant directional sector

The assessment of global directional extreme significant wave height (SWH) is crucial for the ocean infrastructure, which requires the dominant directional sector to be identified. In this study, 40-year (1979–2018) global SWHs and wave directions obtained from ERA5 are employed as the initial database. To study the extreme wave, storms over the initial threshold are extracted, which show that the non-tropical cyclonic storm is stable with the direction and most directions are within the dominant directional sector. Thus, the directional extrapolation is performed based on the independent non-tropical cyclone sample. To identify the dominant directional sector, an automated method is proposed based on the circular mean sample. Benefiting from this method, global patterns of sector width and representative direction of dominant directional sector can be obtained and classified. To make sufficient use of extreme samples for reasonable extrapolation, the peak over threshold method with the generalized Pareto distribution model is employed to evaluate the global directional extreme SWHs. The spatially comparable patterns accord with the distribution of wind zones and reveal the effect of swells in low latitudes, which can be used to realize design optimization and key protection of ocean infrastructures, especially for infrastructures that are not symmetrical.

Roof arc width: The novel calculation method for calculation of patient specific roof arc width in acetabular fractures

PurposeRoof arc angle (RAA) is determined by measuring angle between a vertical line drawn from center of the acetabulum towards the acetabular dome and a second line drawn from center of acetabulum to the fracture through the acetabulum. Joel and Matta demonstrated that when roof arc angle was less than 45° on Pelvic AP and Judet's views, the fracture line is considered to be passing through the weight-bearing dome and require surgical fixation. The main purpose of the study is to calculate patient-specific angle and width for the better evaluation and management of acetabular fractures. MethodsRadiographs of normal hips were retrieved from electronic data and parameters were calculated. Two observers calculated the parameters at two different intervals. Pearson correlation formula was used to find a correlation between groups. ResultsFifty radiographs of 28 patients were reviewed. The mean age of patients was 75.58 years ±13.28. The radius of the acetabulum, the radiographic measurement of sector width for 45° angulation at the roof, and the mathematical calculation for roof arc for 45° angle had significant positive correlation for both observers at two different occasions. ConclusionsThe measured roof arc width ranges from a minimum of 16.20 mm–31.50 mm and the calculated arc width for a 45-degree angle varies from a minimum of 15 mm–25.56 mm. These values are higher than the described values of 10 mm equals to 45 degrees. Hence, the values measured in this study should be considered for decision making in the management of acetabular fractures.

Wind farm power maximization through wake steering with a new multiple wake model for prediction of turbulence intensity

A new multiple wake model is developed for wind farm power prediction and wind farm control. First, numerical simulations are conducted for two wind turbines under different layout sets, and the characteristics of mean velocity and turbulence intensity in multiple wakes are systematically investigated. A new multiple wake model considering the local effective turbulence on the rotor and the wake interaction effects is proposed. The proposed model can favorably predict the mean velocity and turbulence intensity distributions in multiple wake regions, as well as the power production in wind farm comparing with numerical simulations and field measurements. Finally, the new proposed multiple wake model is applied to wind farm modelling and optimization framework, which enables the maximization of wind farm power production by wake steering control. The wind sector width of 2° with the wind speed bin of 0.5 m/s is proposed for the lookup-table-based wake steering optimization. The proposed values reduce the prediction error of annual energy production gain from 34.5% to 3.2% comparing with the conventional values of 5° and 1 m/s. In addition, the yaw offset limit of ±15° is recommended to satisfy both the maximization of power production and the safety requirement of International Electrotechnical Commission (IEC) standard.

Research on the effect of magnet parameters on the isochronous field of a superconducting cyclotron

It is a complicated task to obtain an isochronous field of a cyclotron magnet. Due to non-linear property of iron, iterated simulation of magnet design takes a long time to get an isochronous field. As an example, for a magnet design of a 240 MeV (SC240) superconducting cyclotron, the effect of main parameters of a magnet system on the magnetic field was studied, among them the azimuthal sector width, the spiral sector angle, the gap between sectors, the depth of valley region, the position of the coil, the shape of the coil and the excited current of the superconducting coil. It was found that the azimuthal average magnetic field can be increased by any of the following methods, including enlarging azimuthal width, increasing excited current of the superconducting coil, narrowing of the gap between sectors, reducing the depth of the valley region or decreasing the distance between the coil and the mid-plane. In addition, axial oscillation frequency can be improved by increasing the spiral angle, the depth of the valley region, or decreasing the gap between sectors.

Design study of the KIRAMS-430 superconducting cyclotron magnet

Design study of superconducting cyclotron magnet for the carbon therapy was performed at the Korea Institute of Radiological and Medical Science (KIRAMS). The name of this project is The Korea Heavy Ion Medical Accelerator (KHIMA) project and a fixed frequency cyclotron with four spiral sector magnet was one of the candidate for the accelerator type. Basic parameters of the cyclotron magnet and its characteristics were studied. The isochronous magnetic field which can guide the 12C6+ ions up to 430MeV/u was designed and used for the single particle tracking simulation. The isochronous condition of magnetic field was achieved by optimization of sector gap and width along the radius. Operating range of superconducting coil current was calculated and changing of the magnetic field caused by mechanical deformations of yokes was considered. From the result of magnetic field design, structure of the magnet yoke was planned.

Sector nulling in planar irregular sub‐arrayed sparse array antennas

This study concerns wide angular sector (higher order) null synthesis in planar irregular sparse antenna arrays when aperture distributed sub-arrays are used to reduce the computational load. A hybrid optimisation tool has been used to find array element excitations to achieve as low as possible sector nulls for the desired sector width. Performance comparisons have been made for three sub-array configurations based on the obtained numerical results. Various interference jamming scenarios have been considered including single and dual sectors for single-dimensional ( θ ) (1D) and two-dimensional ( θ , ϕ) (2D) nulls. The proposed optimisation scheme has shown to be successful for the synthesis of 1D and 2D sector nulls with depths as low as −100 dB for the given configuration with reduced computational time when compared with the full array. The comparison of achieved null depths for different sub-array sizes and convergence time has also been presented and discussed.

Abstract 156: Serial Evaluations of Coronary Artery Abnormalities in Kawasaki Disease Patients Should Include Assessment for the Development of Luminal Myofibroblastic Proliferation and Chronic Thromboses: a Preliminary Echocardiographic Study

Introduction: We recently reported that luminal myofibroblastic proliferation (LMP) is an active process of smooth muscle-cell derived myofibroblasts and their matrix products that can cause progressive coronary artery (CA) stenoses in KD patients. Serial echocardiography to assess for high risk CA changes, with periodic cardiac functional assessments in selected patients, is the current standard of care for monitoring patients with CA abnormalities. Monitoring for LMP/chronic thromboses is not routinely performed. Hypothesis: We hypothesized that echocardiographic images from KD children with severe CA abnormalities could suggest the presence of LMP and/or chronic thromboses, indicating the potential for progression to CA stenoses. Methods: We reviewed echocardiographic studies from a convenience sample of 28 KD patients with multiple aneurysms/giant aneurysms, to determine whether LMP and/or thrombosis could be identified on serial imaging. Results: In 12 of the 28 patients, images were highly suggestive of LMP and/or thromboses. This could only be assessed in the proximal segments of the left main, circumflex, left anterior descending and right CAs. Detection was enhanced by optimizing the depth and sector width for the coronary artery segment of interest and use of magnification on the review station. Variations in echocardiographic techniques such as low frequency probes, harmonics, persistence, excessive compress or low gain settings made the assessment difficult. 4 patients in this cohort required CA bypass and 1 died from myocardial infarction due to progressive LMP. Distal vessel occlusion could not be visualized by echocardiography. Conclusions: Images highly suggestive of LMP/chronic thromboses were evident in at least a third of patients with severe CA disease, including one patient who died of progressive LMP stenosis documented at autopsy. Echocardiography could not distinguish between LMP and chronic thrombosis as the cause of CA stenoses. Our study highlights the need for improved serial imaging for ongoing LMP/thromboses in AHA risk group IV. Patients with these complications may require more frequent cardiac functional assessments than are routinely recommended, to avoid adverse outcomes.

Sensitivity Analysis of the VVP Wind Retrieval Method for Single-Doppler Weather Radars

Abstract The sensitivity of the ill-conditioned coefficient matrix (CM) and the size of the analysis volume on the retrieval accuracy in the volume velocity processing (VVP) method are analyzed. By estimating the upper limit of the retrieval error and analyzing the effects of neglected parameters on retrieval accuracy, the simplified wind model is found to decrease the difficulty in solving and stabilizing the retrieval results, even though model errors would be induced by neglecting partial parameters. Strong linear correlation among CM vectors would cause an ill-conditioned matrix when more parameters are selected. By using exact coordinate data and changing the size of the analysis volume, the variation of the condition number indicates that a large volume size decreases the condition number, and the decrease caused by increasing the number of volume gates is larger than that caused by increasing the sector width. Using the spread of errors in the solution, a demonstration using mathematical deduction is provided to explain how a large analysis volume can improve retrieval accuracy. A test with a uniform wind field is used to demonstrate these conclusions.

SCALING OF THE GROWTH RATE OF MAGNETIC ISLANDS IN THE HELIOSHEATH

Current sheets thinner than the ion inertial length are unstable to the tearing instability and will develop magnetic islands that grow due to magnetic reconnection. We investigate whether the growth of magnetic islands in a current sheet can continue indefinitely, or in the case of the heliosheath until reaching a neighboring current sheet, and at what rate the islands grow. We investigate the development and growth of magnetic islands using a particle-in-cell code, starting from particle noise. Performing a scaling of the growth of magnetic islands versus the system size, we find that the growth rate is independent of the system size up to the largest simulation we were able to complete. The islands are able to continue growing as long as they merge with each other and maintain a high aspect ratio. Otherwise there is not enough magnetic tension to sustain reconnection. When applied to the sectored magnetic fields in the heliosheath, we show that the islands can continue growing until they reach the sector width and do so in much less time than it takes for the islands to convect through the heliosheath.

The liver: how we do it.

The liver: how we do it.

In Search of a Holy Grail

“It came out of nowhere and captured the cardiology community by storm.” The cliche seems very appropriate when describing the impact of cardiac resynchronization therapy (CRT) on the treatment of heart failure. CRT improves survival rate in symptomatic patients 1 and is the only nonsurgical technique that provides substantial and stable reverse remodeling in both symptomatic and asymptomatic patients.2,3 The most surprising fact is that this is accomplished through mechanisms that are still unclear and that are not fully elucidated in experimental models. CRT is the only heart failure therapy with a potential to improve survival rate that is not based on neurohormonal modulation. Finally, it represents a challenge to the imaging community, as it establishes a need to measure something that was previously overlooked—dyssynchrony. Article see p 14 Unfortunately, CRT is not universally successful. One third of CRT patients do not feel better,4 and close to 40% of patients do not experience reverse remodeling, which is important because it predicts survival rate.5 This should not be a surprise—treatment of chronic diseases is rarely homogenously beneficial to all the patients. Nevertheless, in the case of CRT, some extra precautions are necessary. CRT is expensive; placement of electrodes may be difficult; and, even in experienced centers, a significant number of patients may require surgical placement. Finally, it is an expensive, healthcare-intensive therapy with extensive follow-up and occasional complications. Thus, there is an ongoing search for practical methods to predict the outcome of CRT and guide its use. Current guidelines use QRS duration (and symptoms) as the principal determinants for implantation, and as noted, this is fairly successful, with two thirds of such patients demonstrating improvement. The real challenge for clinicians comes in two situations: identifying those patients with narrow QRS who are …

Guidelines for the Performance of a Comprehensive Intraoperative Epiaortic Ultrasonographic Examination: Recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists; Endorsed by the Society of Thoracic Surgeons

Guidelines for the Performance of a Comprehensive Intraoperative Epiaortic Ultrasonographic Examination: Recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists; Endorsed by the Society of Thoracic Surgeons

Abstract 1872: New Fusion Technique Significantly Improves Image Quality and Completeness of Datasets in Real Time 3 Dimensional Echocardiography

Introduction: Real time 3 dimensional echocardiography (RT3DE) still presents a challenge for full volume acquisition in many patients because of incomplete datasets due to inadequate sector width and/or limited acoustic windows. Hypothesis: We assessed the hypothesis that fusion of standard datasets from different transducer positions improves the completeness and image quality of RT3DE. Methods: We studied 14 patients (mean age 47.0±22 yrs, 9 men, 5 women) referred for echocardiographic assessment of LV function. Standard full volume RT3DE was performed with an iE33 scanner with X3 probe (Philips Medical Systems, Andover, USA). We fused at least 2 standard RT3DE datasets from different transducer positions using a new, developed on site technique. All standard and fused datasets were processed with research software (Research Arena, TomTec, Germany). Readings were done by an experienced echocardiographer, who graded endocardial border definition and wall thickening: good quality: grade 2; intermediate: 1; poor or out of sector: 0. We studied separately segments in the short axis view (PSAX) and in apical views, yielding 32 segments per patient and total 896 cardiac segments for standard and fused datasets. Results: Table 1 summarizes the segmental quality assessments using the 2 techniques, and the number of segments per patient (mean±SD). Quality gains from grade 0 to 1 and 1 to 2 in the fused images were similarly distributed among PSAX and apical segments. Conclusions: The new fusion technique improved analysis of segmentation of the heart with RT3DE when compared with standard datasets. It increased the number of segments available for assessment and upgraded their image quality. Table 1

Elastic deformation in a crystal plate where lattice–parameter mismatch is present between adjacent growth sectors. I. Anisotropic elasticity theory, with application to lattice-parameter measurements

A method is described for analysing strain in a plate–shaped crystal divided into growth sectors differing in lattice parameter and joined together at coherent dislocation–free sector boundaries running between the surfaces of the plate. The specimen studied was a large synthetic diamond, grown by the high–pressure hightemperature method, from which a near–central slice had been cut and polished parallel to (110). It contained dilatation–producing atomically dispersed substitutional nitrogen impurity, with adjacent growth sectors alternating in nitrogen concentration. In order that stress functions could be used to approximate the exact solution of the three–dimensional problem, the configuration of crystal growth sectors was modelled by an assembly of elongated rectangular parallelepipeds of alternating lattice parameter. Such a model is considered to be a good representation of the sector configuration of special interest in the real crystal. Using this model, the strains induced by lattice–parameter mismatch were calculated by adapting the classical theory of initial stresses due to Timoshenko and Goodier. In the present application, this involved four stages of imaginary operations: disassembly of the crystal model into stress–free sectors, deforming them by uniform lattice–matching strains, in planes parallel to the sector boundaries, ‘welding’ them together, and restoration of the initial conditions by application of ‘annulling’ stresses to cancel those applied in the deformations. Because uniform strains were applied in the matching procedure, only forces on the free surfaces of the crystal were required in this final stage, and it is argued that these should be applied in plane strain in planes orthogonal both to the sector boundaries and to the crystal–plate surface. Stress functions for orthorhombic symmetry are derived from first principles and applied to the geometry of the present problem, namely that of a cubic crystal under plane strain in which the cubic axes are rotated by 45 ° about the axis determined by the sector–boundary normal, [001]. Displacements and strains have been calculated at all points within the sector cross–section of interest, and extended to include wide variations in ratios between sector widths, and between sector width and plate thickness; the physical reasons for the resultant changes in strain distributions are discussed. Convergence of the Fourier–series solution under this variation of parameters is examined in detail. Representative deformation profiles of (110) planes in the real crystal are exhibited. The calculation has enabled a close limit to be placed on systematic error due to coherency strains in the findings of earlier X–ray–diffractometric experiments on the specimen discussed in the present study. Those experiments compared the symmetrical 440 surface Bragg reflection from a large (11 bar 1) growth sector fairly rich in substitutional nitrogen impurity with that from an adjacent, smaller, (11 bar 0) sector, virtually nitrogen free. The measurements aimed to establish the proportionality factor between substitutional nitrogen concentration and dilatation. The present analysis supports the earlier X–ray diffractometry: it changes the finding for Δa 0 /ā 0 quite insignificantly from (1.18 ±) × 10 −5 to (1.20 ± 0.07) × 10 −5 . On the other hand, revision of the nitrogen–concentration difference between the two growth sectors concerned, resulting from a more recent conversion factor between infrared absorption and nitrogen content (independent of the present study), raises that difference from ca .88 to ca .100 ppm atomic. Combining this large change with the small change in Δa 0 /ā 0 reduces the earlier finding for the ratio of the effective volume of a single substitutional nitrogen atom to the volume of the carbon atom it replaces from 1.41 ± 0.06 to 1.36 ± 0.1.

Habitat Matrix Effects on Pond Occupancy in Newts

Abstract: In farmlands, the population viability of many amphibians is suspected to depend on the resistance the matrix of crop fields presents to movements between ponds and terrestrial sites and movements among ponds. Over recent decades the increase in cereal growing at the expense of cattle breeding has caused a drastic change in habitat matrix in many European regions. We investigated the effect of such change on populations of three newt species ( Triturus helveticus, T. alpestris, and T. cristatus) by comparing their abundances in sites that varied in amount of cultivated ground. A multivariate regression analysis of the relationship of newt abundance to both pond and landscape variables demonstrated the negative influence of cultivated ground on abundance. The width of the uncultivated sector linking the pond to the forest was a good predictor of abundance after the influences of both pond area and fish presence were removed. Moreover, newt presence was positively related to the number of ponds within that 50‐ha surrounding area, highlighting the role of metapopulation functioning in newt occupancy of ponds. The relationship between newt abundance and width of uncultivated sectors agrees with present knowledge of the orientation mechanisms that underlie migration movements in urodeles. Such a relationship between connectedness and sector width shows that narrow, linear corridors such as hedgerows may not be useful in newt conservation. Our study also highlights the need to incorporate a behavioral component of habitat use into models of connectivity in conservation biology.

A Complexity Analysis for Directional Parametric Height Field Ray Tracing

It has been shown that height field ray tracing efficiency can be improved by traversing rays in steps across evenly spaced inverted cones of empty space centered above height field cells. This approach, referred to as linear parametric height field ray tracing, has previously been extended by directionalizing the inverted cones, i.e., by allowing the opening angles of the inverted cones to vary between sectors. This paper provides a mathematical analysis of parametric ray tracing complexity as a function of cone sector width and height field resolution. Empirical data on ray tracing run-times and mean lengths of traversal steps along rays during ray tracing is presented. It is shown that parametric height field ray tracing can be substantially more efficient than other popular height field ray tracing methods when cones with narrow sectors are used.

Spectral bandwidths for the detection of color.

The spectral properties of human color detection mechanisms were measured using a noise masking technique that minimizes the possibility of off-axis looking and artifactually narrow estimates of bandwidth. Observers were induced to use a single detection mechanism throughout a spectral bandwidth measurement by using sectored noise to mask a time-varying signal of fixed chromatic properties. Sectored noise draws samples from sectors of variable width in the color plane, centered on the signal axis. Contrast thresholds for equiluminant signals that appeared yellow, orange, red and violet were found to depend on the power of the noise, projected along the chromatic axis of the signal, but not on the sector width of the noise. These results are consistent with the activity of spectrally broadband, linear detection mechanisms that are tuned to the signal color directions tested.