scholarly journals Variation in thyroid volumes due to differences in the measured length or area of the cross‐sectional plane: A validation study of the ellipsoid approximation method using CT images

2021 ◽  
Vol 22 (4) ◽  
pp. 15-25
Author(s):  
Naotoshi Fujita ◽  
Katsuhiko Kato ◽  
Shinji Abe ◽  
Shinji Naganawa
Keyword(s):  
Approximation Method ◽  
Validation Study ◽  
Ct Images ◽  
Cross Sectional ◽  
Sectional Plane ◽  
The Cross ◽  
Measured Length

scholarly journals Variation in thyroid volumes due to differences in the measured length or area of the cross-sectional plane: A validation study of the ellipsoid approximation method using CT images.

2020 ◽  
Author(s):  
Naotoshi Fujita ◽  
Katsuhiko Kato ◽  
Shinji Abe ◽  
Shinji Naganawa
Keyword(s):  
Approximation Method ◽  
Three Dimensional ◽  
Thyroid Volume ◽  
Major Axis ◽  
Ct Images ◽  
Maximum Diameter ◽  
Cross Sectional ◽  
Sectional Plane ◽  
The Cross ◽  
Measured Length

Abstract Background This study examined the variation in the thyroid volume determined by the ellipsoid approximation method due to differences in the measured length or area of the cross-sectional plane of CT images. Methods Forty-five patients with Graves' diseasewere included in this retrospective study. We designated the three-dimensional thyroid volumes extracted manually (VCT) as the reference data and calculated five approximate volumes for comparison: (1) the mean volume of 8100 different thyroid volumes depending on the diameter of the cross-sectional plane at the midpoint of the major axis, (Vellipsoid,mean); (2) the volume using the maximum diameter and its orthogonal diameter, (Vellipsoid,maxlength); (3) the maximum (Vellipsoid,maxvolume) and (4) minimum (Vellipsoid,minvolume) of the 8100 thyroid volumes; and (5) the volume determined with an equivalent circle diameter, (Vellipsoid,Heywood). Results Thyroid volumes obtained via the ellipsoid approximation method varied depending on the diameter of the cross-sectional plane and included a mean error of approximately 20%, while the concordance correlation coefficient (CCC) differed for each approximate volume. Among these volumes, Vellipsoid,meanand Vellipsoid,Heywoodwere in good agreement with VCT, according to single regression analyses and the resultant CCC values, with mean errors of 7.0% and 2.5%, respectively. Conclusion WhileVellipsoid,Heywoodapproximated thyroid volumes with vastly reduced errors, we recommend utilizing three-dimensional thyroid volumetry if measurement accuracy is required.

Usefulness of Coronal Reconstruction CT Images for Quantitative Evaluation of the Cross-Sectional Area of Small Pulmonary Vessels

2014 ◽  
Vol 21 (11) ◽  
pp. 1411-1415 ◽  
Author(s):  
Shin Matsuoka ◽  
Tsuneo Yamashiro ◽  
Shoichiro Matsushita ◽  
Akiyuki Kotoku ◽  
Atsuko Fujikawa ◽  
...  
Keyword(s):  
Quantitative Evaluation ◽  
Ct Images ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Pulmonary Vessels ◽  
The Cross

Formation and decay of coherent structures in pipe flow

2010 ◽  
Vol 655 ◽  
pp. 258-279 ◽  
Author(s):  
JIMMY PHILIP ◽  
JACOB COHEN
Keyword(s):  
Coherent Structures ◽  
Pipe Flow ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Hairpin Vortices ◽  
Cross Sectional ◽  
Instability Waves ◽  
Sectional Plane ◽  
The Cross ◽  
Three Dimensional Coordinate

Experimental investigation of the generation and decay of coherent structures, namely, streaks (accompanied by a counter-rotating vortex pair) and hairpin vortices in pipe flow, is carried out by artificial injection of continuous disturbances. Flow visualization and velocity measurements show that for small amplitudes of disturbances (v0) streaks are produced, and increasing v0 produces instability waves on the streaks, which further break down into an array of hairpin vortices. However, the streaks and hairpins decay along the downstream direction (X). In fact, the critical value of v0 required for the initiation of hairpins at a given Re (Reynolds number) varies with the streamwise distance (in contrast to the previously found scaling of v0 ~ Re−1, valid only close to the location of injection, i.e. smaller X). This is a consequence of the decay of the coherent structures in the pipe. Moreover, the hairpins have been found to decay more slowly with increasing Re. Measurements of energy in the cross-sectional plane of the pipe, and maps of disturbance velocity at various X-locations show the transient growth and decay of energy for relatively low v0. For higher v0 and Re the energy has been seen to increase continuously along the length of the pipe under observation. Owing to the increase in the cross-sectional area occupied by the disturbance along the X-direction, it is observed that energy can transiently increase even when the total disturbance magnitude is decreasing. Observing the similarity of the present work and other investigations wherein decay of turbulence in pipe flow is found, a schematic illustration of the transition surface for pipe flow on a v0−Re−X, three-dimensional coordinate system is presented.

scholarly journals A Spectral Finite Element Model for Vibration Analysis of a Beam Based on General Higher-Order Theory

2008 ◽  
Vol 15 (2) ◽  
pp. 179-192 ◽  
Author(s):  
Jiao Sujuan ◽  
Li Jun ◽  
Hua Hongxing ◽  
Shen Rongying
Keyword(s):  
Cross Section ◽  
Spectral Element ◽  
Higher Order ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Coupled Equations ◽  
Aspect Ratios ◽  
Sectional Plane ◽  
The Cross ◽  
Element Matrix

The spectral element matrix is derived for a straight and uniform beam element having an arbitrary cross-section. The general higher-order beam theory is used, which accurately accounts for the transverse shear deformation out of the cross-sectional plane and antielastic-type deformation within the cross-sectional plane. Two coupled equations of motion are derived by use of Hamilton's principle along with the full three-dimensional constitutive relations. The theoretical expressions of the spectral element matrix are formulated from the exact solutions of the coupled governing equations. The developed spectral element matrix is directly applied to calculate the exact natural frequencies and mode shapes of the illustrative examples. Numerical results of the thick isotropic beams with rectangular and elliptical cross-sections are presented for a wide variety of cross-section aspect ratios.

Influence of meniscus shape in the cross sectional plane on the knee contact mechanics

2015 ◽  
Vol 48 (8) ◽  
pp. 1356-1363 ◽  
Author(s):  
Piotr Łuczkiewicz ◽  
Karol Daszkiewicz ◽  
Wojciech Witkowski ◽  
Jacek Chróścielewski ◽  
Witold Zarzycki
Keyword(s):  
Contact Mechanics ◽  
Cross Sectional ◽  
Meniscus Shape ◽  
Sectional Plane ◽  
The Cross

Investigation of Flow Structure to Prevent Thermal Fatigue in a Downward Branch Pipe With a Closed End

2017 ◽  
Author(s):  
Koji Miyoshi ◽  
Akira Nakamura
Keyword(s):  
Penetration Depth ◽  
Flow Structure ◽  
Thermal Fatigue ◽  
Branch Pipe ◽  
Swirl Flow ◽  
Main Flow ◽  
Cross Sectional ◽  
Fluctuation Range ◽  
Sectional Plane ◽  
The Cross

Many pipes branch off from the main pipes in power plants. Main flow with high velocity initiates a cavity flow in a downward branch pipe with a closed end. Hot water penetrates into the branch pipe and a thermally stratified layer forms in the branch pipe if the main flow is hot. Fluctuations of the thermally stratified layer may initiate wall temperature fluctuations and thermal fatigue cracks in the branch pipe. Penetration depth of the main flow and the fluctuation characteristics into the branch pipe with a closed end were investigated by experiments. Experiments were conducted for various inner diameters of a branch pipe and main flow velocities under room temperature conditions. Flow structure was observed by test section made of acrylic resin. A tracer method was used to measure the penetration depth of the main flow. The penetration depth of the main flow changed periodically. The maximum penetration depth of the main flow was correlated by the Reynolds number. The fluctuation range and period of the penetration depth were also investigated. Next, the flow patterns on the cross-sectional plane in the branch pipe were observed to investigate the fluctuation mechanism of penetration depth. Three flow patterns were observed on the cross-sectional plane in the branch pipe. They were flow parallel to the cross-sectional direction, flow consisting of small vortexes and large swirl flow. The generation period of the large swirl flow was nearly equal to the fluctuation period of the penetration depth. The fluctuation range of the penetration depth and the duration showed similar trends for different inner diameters of the branch pipe. These results showed that the fluctuation of the penetration depth was caused by the periodic generation of the large swirl flow.

scholarly journals Flush Flow Behaviour Affected by the Morphology of Intravascular Endoscope: A Numerical Simulation and Experimental Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Yujie Li ◽  
Mingzi Zhang ◽  
Simon Tupin ◽  
Kohei Mitsuzuka ◽  
Toshio Nakayama ◽  
...  
Keyword(s):  
Computational Models ◽  
Volume Fraction ◽  
High Volume ◽  
Strong Impact ◽  
Cross Sectional ◽  
Injection Speed ◽  
Vascular Segment ◽  
Sectional Plane ◽  
The Cross

Background: Whilst intravascular endoscopy can be used to identify lesions and assess the deployment of endovascular devices, it requires temporary blockage of the local blood flow during observation, posing a serious risk of ischaemia.Objective: To aid the design of a novel flow-blockage-free intravascular endoscope, we explored changes in the haemodynamic behaviour of the flush flow with respect to the flow injection speed and the system design.Methods: We first constructed the computational models for three candidate endoscope designs (i.e., Model A, B, and C). Using each of the three endoscopes, flow patterns in the target vessels (straight, bent, and twisted) under three different sets of boundary conditions (i.e., injection speed of the flush flow and the background blood flowrate) were then resolved through use of computational fluid dynamics and in vitro flow experiments. The design of endoscope and its optimal operating condition were evaluated in terms of the volume fraction within the vascular segment of interest, as well as the percentage of high-volume-fraction area (PHVFA) corresponding to three cross-sectional planes distal to the microcatheter tip.Results: With a mild narrowing at the endoscope neck, Model B exhibited the highest PHVFA, irrespective of location of the cross-sectional plane, compared with Models A and C which, respectively, had no narrowing and a moderate narrowing. The greatest difference in the PHVFA between the three models was observed on the cross-sectional plane 2 mm distal to the tip of the microcatheter (Model B: 33% vs. Model A: 18%). The background blood flowrate was found to have a strong impact on the resulting volume fraction of the flush flow close to the vascular wall, with the greatest difference being 44% (Model A).Conclusion: We found that the haemodynamic performance of endoscope Model B outperformed that of Models A and C, as it generated a flush flow that occupied the largest volume within the vascular segment of interest, suggesting that the endoscope design with a diameter narrowing of 30% at the endoscope neck might yield images of a better quality.

Flow and Mixing in Rotating Zigzag Microchannel

2017 ◽  
Author(s):  
Yong Ren ◽  
Wallace Woon-Fong Leung
Keyword(s):  
Numerical Model ◽  
Cross Flow ◽  
Centrifugal Acceleration ◽  
Cross Sectional ◽  
Coriolis Acceleration ◽  
Rotation Direction ◽  
Mixing Quality ◽  
Sectional Plane ◽  
The Cross

The flow and mixing in rotating zigzag microchannel is investigated experimentally and numerically with objective of improving mixing, which is largely due to secondary or cross-flow in the cross-sectional plane of the channel and the bend connecting non-radial angled channel segments. Unlike the conventional stationary zigzag channel, crossflow in the zigzag channel is highly intensified from a combination of (a) centrifugal acceleration component in the cross-sectional plane due to the angled channel segments, (b) centrifugal acceleration generating Görtler vortices at “channel bends”, and (c) Coriolis acceleration. When the channel segment in the zigzag channel is inclined towards rotation direction (prograde), all three accelerations are aligned intensifying the crossflow; however, when it is inclined opposite to rotation (retrograde), Coriolis acceleration negates the other two accelerations reducing mixing. A numerical model has been developed accurately accounting for the interactions of throughflow, crossflow and material dispersion by diffusion and convection in a rotational platform. An experimental microfluidic platform with rotating zigzag microchannel has also been developed. Experimental results on mixing quality carried out at two rotation speeds compared well with prediction from the numerical model. The overall mixing quality of a rotating zigzag channel is much improved compared with that of a stationary zigzag channel.

scholarly journals Effect of inertial lift on a spherical particle suspended in flow through a curved duct

2019 ◽  
Vol 875 ◽  
pp. 1-43 ◽  
Author(s):  
Brendan Harding ◽  
Yvonne M. Stokes ◽  
Andrea L. Bertozzi
Keyword(s):  
Reynolds Number ◽  
Spherical Particle ◽  
Cross Section ◽  
Bend Radius ◽  
Cross Sectional ◽  
Particle Reynolds Number ◽  
Curved Duct ◽  
Sectional Plane ◽  
Flow Through ◽  
The Cross

We develop a model of the forces on a spherical particle suspended in flow through a curved duct under the assumption that the particle Reynolds number is small. This extends an asymptotic model of inertial lift force previously developed to study inertial migration in straight ducts. Of particular interest is the existence and location of stable equilibria within the cross-sectional plane towards which particles migrate. The Navier–Stokes equations determine the hydrodynamic forces acting on a particle. A leading-order model of the forces within the cross-sectional plane is obtained through the use of a rotating coordinate system and a perturbation expansion in the particle Reynolds number of the disturbance flow. We predict the behaviour of neutrally buoyant particles at low flow rates and examine the variation in focusing position with respect to particle size and bend radius, independent of the flow rate. In this regime, the lateral focusing position of particles approximately collapses with respect to a dimensionless parameter dependent on three length scales: specifically, the particle radius, duct height and duct bend radius. Additionally, a trapezoidal-shaped cross-section is considered in order to demonstrate how changes in the cross-section design influence the dynamics of particles.

On Saint-Venant’s Problem for an Inhomogeneous, Anisotropic Cylinder—Part II: Cross-Sectional Properties

2000 ◽  
Vol 68 (3) ◽  
pp. 382-391 ◽  
Author(s):  
J. B. Kosmatka ◽  
H. C. Lin ◽  
S. B. Dong
Keyword(s):  
Cross Section ◽  
Symmetry Plane ◽  
Material Symmetry ◽  
Shear Center ◽  
Cross Sectional ◽  
Mean Values ◽  
Anisotropic Cylinder ◽  
Sectional Plane ◽  
Weighted Integrals ◽  
The Cross

Cross-sectional properties of a prismatic inhomogeneous, anisotropic cylinder are determined from Saint-Venant solutions for extension-bending-torsion and flexure, whose method of construction was presented in a previous paper. The coupling of extensional, bending, and twisting deformations due to anisotropy and inhomogeneity leads to some very interesting features. Herein, it is shown that for an inhomogeneous, anisotropic cylinder whose cross-sectional plane is not a material symmetry plane, distinct modulus-weighted and compliance-weighted centroids and distinct principal bending axes are possible. A line of extension-bending centers is given on which an axial force causes extension and bending only but no twist. Two shear centers are given, one using the Griffith-Taylor definition that ignores cross-sectional warpages and the other by stipulating a zero mean rotation over the cross section. The center of twist is discussed, and this property depends on root end fixity conditions that are prescribed in terms of their mean values based on integrals over the cross section rather than by a pointwise specification. While these shear center and center of twist definitions have some rational bases, it is recognized that other definitions are possible, for example those based on modulus or compliance-weighted integrals. Two examples, an angle and a channel, both composed of a two-layer ±30 deg angle-ply composite material, illustrate the procedures for determining these cross-sectional properties.

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