Unusual Flow Patterns Research Articles

Abstract 15341: Persistent Fifth Arch as an Aortopulmonary Connection in a Case of Tetralogy of Fallot

Persistent fifth aortic arch is a heterogeneous vascular anomaly with variable anatomical presentations and physiological consequences. This unusual embryological remnant represents a management challenge, particularly in critical right sided obstructive heart lesions where accurate delineation of sources of pulmonary blood flow is essential. This is a newborn 2 kg premature male born at 34 weeks of gestation with prenatally diagnosed tetralogy of Fallot. Post-natal echocardiogram confirmed diagnosis with evidence of moderate-to-severe pulmonary stenosis, restrictive ventricular septal defect, and a right aortic arch. CT angiogram ordered to delineate the head and neck vessel anatomy showed an exceedingly rare finding of an isolated connection of the left subclavian artery (LSCA) to the main pulmonary artery (MPA) via a left sided ductus arteriosus. Blood flowed from the common carotid arteries, through the circle of Willis, and, in a retrograde direction, into the LSCA. Prostaglandin E was initiated due to concern for ductal dependent pulmonary blood flow, but after clinical observation it was discontinued without subsequent onset of cyanosis. Repeat echocardiograms were reassuring in showing persistence of the left ductus arteriosus. The patient was discharged home at 5 weeks-old and at 4 months-old he underwent complete repair after developing progressive desaturations and worsening sub-valvar and valvar pulmonary stenosis. The surgical repair included ventricular septal defect closure, transannular patch, extensive right ventricular myomectomy and reimplantation of LSCA onto the left common carotid artery. The post-operative course was uncomplicated. This rare case of persistent fifth aortic arch with retrograde flow to the LSCA demonstrates the complementary roles of noninvasive imaging modalities in guiding medical therapy and surgical management. This unusual blood flow pattern and initial concern for duct dependent pulmonary blood flow complicated early management, but a conservative approach with repeat imaging allowed for eventual complete repair.

Scanning Ion Conductance Microscopy: Surface Charge Effects on Electroosmotic Flow Delivery from a Nanopipette.

Scanning ion conductance microscopy (SICM) is a powerful and versatile technique that allows an increasingly wide range of interfacial properties and processes to be studied. SICM employs a nanopipette tip that contains electrolyte solution and a quasi-reference counter electrode (QRCE), to which a potential is applied with respect to a QRCE in a bathing solution, in which the tip is placed. The work herein considers the potential-controlled delivery of uncharged electroactive molecules (solute) from an SICM tip to a working electrode substrate to determine the effect of the substrate on electroosmotic flow (EOF). Specifically, the local delivery of hydroquinone from the tip to a carbon fiber ultramicroelectrode (CF UME) provides a means of quantifying the rate of mass transport from the nanopipette and mapping electroactivity via the CF UME current response for hydroquinone oxidation to benzoquinone. EOF, and therefore species delivery, has a particularly strong dependence on the charge of the substrate surface at close nanopipette-substrate surface separations, with implications for retaining neutral solute within the tip predelivery and for the delivery process itself, both controlled via the applied tip potential. Finite element method (FEM) simulations of mass transport and reactivity are used to explain the experimental observations and identify the nature of EOF, including unusual flow patterns under certain conditions. The combination of experimental results with FEM simulations provides new insights on mass transport in SICM that will enhance quantitative applications and enable new possibilities for the use of nanopipettes for local delivery.

Efficient blood flow visualization using flowline extraction and opacity modulation based on vascular structure analysis

With the recent advances regarding the acquisition and simulation of blood flow data, blood flow visualization has been widely used in medical imaging for the diagnosis and treatment of pathological vessels. In this paper, we present a novel method for the visualization of the blood flow in vascular structures. The vessel inlet or outlet is first identified using the orthogonality metric between the normal vectors of the flow velocity and vessel surface. Then, seed points are generated on the identified inlet or outlet by Poisson disk sampling. Therefore, it is possible to achieve the automatic seeding that leads to a consistent and faster flow depiction by skipping the manual location of a seeding plane for the initiation of the line integration. In addition, the early terminated line integration in the thin curved vessels is resolved through the adaptive application of the tracing direction that is based on the flow direction at each seed point. Based on the observation that blood flow usually follows the vessel track, the representative flowline for each branch is defined by the vessel centerline. Then, the flowlines are rendered through an opacity assignment according to the similarity between their shape and the vessel centerline. Therefore, the flowlines that are similar to the vessel centerline are shown transparently, while the different ones are shown opaquely. Accordingly, the opacity modulation method enables the flowlines with an unusual flow pattern to appear more noticeable, while the visual clutter and line occlusion are minimized. Finally, Hue-Saturation-Value color coding is employed for the simultaneous exhibition of flow attributes such as local speed and residence time. The experiment results show that the proposed technique is suitable for the depiction of the blood flow in vascular structures. The proposed approach is applicable to many kinds of tubular structures with embedded flow information.

Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

Stress-induced anisotropic diffusion in alloys: Complex Si solute flow near a dislocation core in Ni

Stress introduces anisotropy in the transport coefficients in materials, affecting diffusion. Using first-principles quantum-mechanical methods for activation barriers of atomic jumps, combined with the extended self-consistent mean-field theory to compute transport coefficients with strain-reduced symmetry, we predict significant stress-induced anisotropy for Si impurity diffusion in nickel. This causes complex spatial- and temperature-dependent fluxes; as an example, the heterogenous strain field of a dislocation creates unusual flow patterns that affect mechanical and segregation behavior.

An investigation of flow patterns and hardness distributions using different anvil alignments in high-pressure torsion

A super duplex stainless steel was selected as a model material to evaluate the origins of unusual double-swirl flow patterns that have been reported on the upper surfaces of discs processed by high-pressure torsion (HPT). The experiments were conducted by making changes in the anvil alignment prior to HPT processing. Experiments were conducted under two different conditions: using essentially a perfect anvil alignment and with an initial anvil misalignment of 100 μm. The experimental results show that no double swirls are visible on the surfaces of discs processed under conditions of perfect anvil alignment but double swirls become visible when processing with a misalignment of 100 μm. The presence of double swirls also affects the measured hardness distributions, and for a misalignment of 100 μm the hardness distribution along a diameter may be non-symmetric with respect to the centre of the disc.

Jugular Venous Reflux in Total Global Amnesia: Simultaneous TCD Bubble Test and Carotid/Jugular Duplex Examination

PurposeWe report an unusual case of venous reflux in a patient with memory loss and focal deficits who was found with an unusual flow pattern on Transcranial Doppler bubble test (TCD-BT) where venous bubbles were found and later confirmed on carotid/jugular duplex (CJD) examination. While chronic Cerebral Spinal Venous Insufficiency (CCSVI) is now a fashionable finding in Multiple Sclerosis, other neurological disease should not be forgotten.Material & MethodsA 22-year-old male presented after multiple episodes of right-side weakness and memory loss associated with repetitive questioning during these episodes. The family also reported that the patient had episodes of isolated, transient memory problems that were not associated with weakness. TCD-BT was performed with 10cc agitated saline test in sitting position. TCD-BT test was performed in the supine position simultaneously with CJD.ResultsTCD-BT shows venous embolization but only minimal arterial embolization in the brain, which could be a potential pitfall for Patent Foramen Ovale (PFO) detection. Carotid/jugular duplex (CJD) examinations revealed cranial flow in the jugular vein during Valsalva maneuver.ConclusionJugular reflux is a poorly understood mechanism of cerebral dysfunction. Cerebral congestion caused by venous reflux is reported in total global amnesia (TGA), but this is the first report on TCD bubble test. CJD assisted with understanding the unusual TCD-BT finding might result in new applications for different neurological diseases. PurposeWe report an unusual case of venous reflux in a patient with memory loss and focal deficits who was found with an unusual flow pattern on Transcranial Doppler bubble test (TCD-BT) where venous bubbles were found and later confirmed on carotid/jugular duplex (CJD) examination. While chronic Cerebral Spinal Venous Insufficiency (CCSVI) is now a fashionable finding in Multiple Sclerosis, other neurological disease should not be forgotten. We report an unusual case of venous reflux in a patient with memory loss and focal deficits who was found with an unusual flow pattern on Transcranial Doppler bubble test (TCD-BT) where venous bubbles were found and later confirmed on carotid/jugular duplex (CJD) examination. While chronic Cerebral Spinal Venous Insufficiency (CCSVI) is now a fashionable finding in Multiple Sclerosis, other neurological disease should not be forgotten. Material & MethodsA 22-year-old male presented after multiple episodes of right-side weakness and memory loss associated with repetitive questioning during these episodes. The family also reported that the patient had episodes of isolated, transient memory problems that were not associated with weakness. TCD-BT was performed with 10cc agitated saline test in sitting position. TCD-BT test was performed in the supine position simultaneously with CJD. A 22-year-old male presented after multiple episodes of right-side weakness and memory loss associated with repetitive questioning during these episodes. The family also reported that the patient had episodes of isolated, transient memory problems that were not associated with weakness. TCD-BT was performed with 10cc agitated saline test in sitting position. TCD-BT test was performed in the supine position simultaneously with CJD. ResultsTCD-BT shows venous embolization but only minimal arterial embolization in the brain, which could be a potential pitfall for Patent Foramen Ovale (PFO) detection. Carotid/jugular duplex (CJD) examinations revealed cranial flow in the jugular vein during Valsalva maneuver. TCD-BT shows venous embolization but only minimal arterial embolization in the brain, which could be a potential pitfall for Patent Foramen Ovale (PFO) detection. Carotid/jugular duplex (CJD) examinations revealed cranial flow in the jugular vein during Valsalva maneuver. ConclusionJugular reflux is a poorly understood mechanism of cerebral dysfunction. Cerebral congestion caused by venous reflux is reported in total global amnesia (TGA), but this is the first report on TCD bubble test. CJD assisted with understanding the unusual TCD-BT finding might result in new applications for different neurological diseases. Jugular reflux is a poorly understood mechanism of cerebral dysfunction. Cerebral congestion caused by venous reflux is reported in total global amnesia (TGA), but this is the first report on TCD bubble test. CJD assisted with understanding the unusual TCD-BT finding might result in new applications for different neurological diseases.

New Developments in the Processing of Bulk Nanoscale Metals Using High-Pressure Torsion

High-pressure torsion is a processing technique involving the application of a high pressure with concurrent torsional straining. Excellent grain refinement may be achieved using this process with the average grain size often reduced to the nanoscale range. Although this processing is expected to lead to significant microstructural inhomogeneity, experiments consistently demonstrate a gradual evolution towards a homogeneous structure. Recent results have also revealed unusual flow patterns in HPT processing including grain agglomeration in a two-phase alloy and the development of double-swirls and vortices in a stainless steel.

Unusual macroscopic shearing patterns observed in metals processed by high-pressure torsion

A duplex stainless steel was processed by high-pressure torsion (HPT) and then examined by optical microscopy. The results reveal unusual flow patterns including double-swirl strains, shear vortices, and the presence of significant local turbulence. Similar flow behavior was also visible in disks of high-purity aluminum and a Zn–22%Al eutectoid alloy. These complex flow patterns and the presence of double-swirls are consistent with the presence of a Kelvin–Helmholtz instability during HPT processing where this may arise if there are local shear velocity gradients between adjacent positions within the HPT disks.

Detection of unusual optical flow patterns by multilevel hidden Markov models

The analysis of motion information is one of the main tools for the understanding of complex behaviors in video. However, due to the quality of the optical flow of low-cost surveillance camera systems and the complexity of motion, new robust image-processing methods are required to generate reliable higher-level information. In our novel approach there is no need for tracking objects (vehicles, pedestrians) in order to recognize anomalous motion, but dense optical flow information is used to construct mixtures of Gaussians, which are analyzed temporally. We create a multilevel model, where low-level states of non-overlapping image regions are modeled by continuous hidden Markov models (HMMs). From low-level HMMs we compose high-level HMMs to analyze the occurrence of the low-level states. The processing of large numbers of data in traditional HMMs can result in a precision problem due to the multiplication of low probability values. Thus, besides introducing new motion models, we incorporate a scaling technique into the mathematical model of HMMs to avoid precision problems and to get an effective tool for the analysis of large numbers of motion vectors. We illustrate the use of our models with real-life traffic videos.

Peculiar flow patterns of RBCs suspended in viscous fluids and perfused through a narrow tube (25 μm)

Red blood cells (RBCs) generally deform to adopt a parachute-like, torpedo-like, or other configuration to align and flow through a capillary that is narrower than their major axis. As described herein, even in a narrow tube (25 microm) with diameter much larger than that of a capillary, flowing RBCs at 1 mm/s align axially and deform to a paraboloid shape in a viscous Newtonian fluid (505 kDa dextran medium) with viscosity of 23.4-57.1 mPa.s. A high-speed digital camera image showed that the silhouette of the tip of RBCs fits a parabola, unlike the shape of RBCs in capillaries, because of the longer distance of the RBC-free layer between the tube wall and the RBC surface ( approximately 8.8 microm). However, when RBCs are suspended in a "non-Newtonian" viscous fluid (liposome-40 kDa dextran medium) with a shear-thinning profile, they migrate toward the tube wall to avoid the axial lining, as "near-wall-excess," which is usually observed for platelets. This migration results from the presence of flocculated liposomes at the tube center. In contrast, such near-wall excess was not observed when RBCs were suspended in a nearly Newtonian liposome-albumin medium. Such unusual flow patterns of RBCs would be explainable by the principle; a larger particle tends to flow near the centerline, and a small one tends to go to the wall to flow with least resistance. However, we visualized for the first time the complete axial aligning and near-wall excess of RBCs in the noncapillary size tube in some extreme conditions.

Cardiac Flow Analysis Applied to Phase Contrast Magnetic Resonance Imaging of the Heart

Phase contrast magnetic resonance imaging is performed to produce flow fields of blood in the heart. The aim of this study is to demonstrate the state of change in swirling blood flow within cardiac chambers and to quantify it for clinical analysis. Velocity fields based on the projection of the three dimensional blood flow onto multiple planes are scanned. The flow patterns can be illustrated using streamlines and vector plots to show the blood dynamical behavior at every cardiac phase. Large-scale vortices can be observed in the heart chambers, and we have developed a technique for characterizing their locations and strength. From our results, we are able to acquire an indication of the changes in blood swirls over one cardiac cycle by using temporal vorticity fields of the cardiac flow. This can improve our understanding of blood dynamics within the heart that may have implications in blood circulation efficiency. The results presented in this paper can establish a set of reference data to compare with unusual flow patterns due to cardiac abnormalities. The calibration of other flow-imaging modalities can also be achieved using this well-established velocity-encoding standard.

Abnormal Flow in the Posterior Descending Artery: An Echo Doppler Clue to the Anomalous Origin of Left Anterior Descending Coronary Artery from the Pulmonary Trunk

Anomalous origin of the left anterior descending coronary (LAD) from the pulmonary trunk is a rare lesion. We describe a neonate with anomalous origin of the LAD from the pulmonary artery and the circumflex artery arising normally from the left-facing sinus. The finding of a tortuous and dilated posterior descending coronary artery suggested increased intercoronary collateral flow and provided a clue to the identification of the anomaly in an otherwise asymptomatic neonate. Interrogation of the posterior descending coronary artery should be included in the routine echocardiographic examination of children, as unusual flow patterns may help identify aberrant coronary artery connections.

Impact of thixotropy on flow patterns induced in a stirred tank: Numerical and experimental studies

Agitation of a thixotropic shear-thinning fluid exhibiting a yield stress is investigated both experimentally and via simulations. Steady-state experiments are conducted at three impeller rotation rates (1, 2 and 8 s −1) for a tank stirred with an axial-impeller and flow-field measurements are made using particle image velocimetry (PIV) measurements. Three-dimensional numerical simulations are also performed using the commercial CFD code ANSYS CFX10.0. The viscosity of the suspension is determined experimentally and is modelled using two shear-dependant laws, one of which takes into account the flow instabilities of such fluids at low shear rates. At the highest impeller speed, the flow exhibits the familiar outward pumping action associated with axial-flow impellers. However, as the impeller speed decreases, a cavern is formed around the impeller, the flow generated in the vicinity of the agitator reorganizes and its pumping capacity vanishes. An unusual flow pattern, where the radial velocity dominates, is observed experimentally at the lowest stirring speed. It is found to result from wall slip effects. Using blades with rough surfaces prevents this peculiar behaviour and mainly resolves the discrepancies between the experimental and computational results.

Isolated left pulmonary artery stenosis due to extrinsic compression by intra thoracic tumor: recognition of unusual Doppler flow pattern and correlation with computed tomography

Pulmonary artery compression in adults resulting from tumors is an uncommon condition often associated with poor prognosis. Among the imaging modalities used for diagnosis, the role of trans thoracic echocardiography in identifying secondary pulmonic stenosis due to extrinsic or intrinsic compression and more importantly the physiologic significance has been increasingly recognized. We describe here a case of isolated left pulmonary artery stenosis which was initially suspected based on classic echocardiographic features of obstruction of pulmonary artery and subsequently confirmed by CT imaging. This case illustrates the versatility of trans thoracic echocardiography in diagnosing incidental abnormalities with potential significant consequences.

The “A-dip” of diastolic mitral regurgitation: An unusual Doppler flow pattern in a patient with severe aortic insufficiency and complete heart block

This is an unusual case of diastolic mitral regurgitation (MR) with a high diastolic velocity jet and prolonged jet duration related to a combination of acute severe aortic insufficiency and high-degree atrioventricular block. This case illustrates an interesting hemodynamic phenomenon with multiple transient decreases in the pressure gradient between the left ventricle and left atrium during diastole related to a temporary increase in left atrial pressure associated with atrial contraction.

Pulmonary Vein Compression by Tumor: An Unusual Doppler Flow Pattern

Pulmonary venous compression caused by a large lung mass was diagnosed in a 50-year-old female with metastatic renal cell carcinoma. The pulmonary venous flow pattern on Doppler revealed high flow velocity as well as the unusual finding of continued antegrade flow throughout the cardiac cycle (without reversal during atrial contraction). Extracardiac tumors can compress pulmonary veins, mimicking pulmonary vein stenosis. This may cause dyspnea due to elevated pulmonary venous pressures. This report describes an unusual pulmonary vein blood flow pattern in a patient with lung metastases.

Varices of inferior epigastric veins caused by chronic inferior vena cava obstruction: Mimicking normal venous flow pattern on radionuclide venography

A 21-year-old patient with long-standing inferior vena cava obstruction secondary to idiopathic thrombosis extending from the external iliac veins underwent a radionuclide venography with Tc-99m pertechnetate labeled erythrocytes. The blood pool phase of the study revealed bilaterally distorted inferior epigastric veins mimicking normal venous flow pattern. The authors present this case to discuss the possible alternative routes and the underlying physiopathologic mechanism of this unusual flow pattern in chronic inferior vena cava obstruction.

Bilateral pulmonary artery compression and obstruction by tumor: Diagnosis by unusual Doppler flow patterns

Pulmonary artery obstruction may be caused by tumor within or external to the arteries. Presented here is a patient with life-threatening compromise in pulmonary flow that was caused by a pulmonary neoplasm. The Doppler echocardiogram showed subtotal narrowing of the right pulmonary artery and total occlusion of the left pulmonary artery. In addition, the beneficial effects of chemotherapy were documented by Doppler. (J Am Soc Echocardiogr 2003;16:185-7.)

Voltage problems on transmission networkd subject to unusual power flow patterns

Voltage problems on transmission networkd subject to unusual power flow patterns