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https://www.readbyqxmd.com/read/28961110/non-invasive-vascular-modulography-method-for-imaging-the-local-elasticity-of-atheroscle-rotic-plaques-simulation-and-in-vitro-vessel-phantom-study
#1
Jonathan Poree, Boris Chayer, Gilles Soulez, Jacques Ohayon, Guy Cloutier
Mechanical and morphological characterization of atherosclerotic lesions in carotid arteries remains an essential step for the evaluation of rupture prone plaques and the preven-tion of strokes. In this study, we propose a non-invasive imaging modulography method (NIV-iMod), which is able of reconstruct-ing a heterogeneous Young's modulus distribution of a carotid plaque from the Von Mises strain elastogram. Elastograms were computed with non-invasive ultrasound images using the La-grangian speckle model estimator (LSME) and a dynamic seg-mentation-optimization procedure to highlight mechanical heter-ogeneities...
September 28, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28887857/development-of-a-patient-specific-atrial-phantom-model-for-planning-and-training-of-inter-atrial-interventions
#2
Pedro Morais, João Manuel R S Tavares, Sandro Queirós, Fernando Veloso, Jan D'hooge, João L Vilaça
BACKGROUND: Several authors have presented cardiac phantoms to mimic the particularities of the heart, making it suitable for medical training and surgical planning. Although the initial models were mainly focused on the ventricles, personalized phantoms of the atria were recently presented. However, such models are typically rigid, the atrial wall is not realistic and they are not compatible with ultrasound (US), being sub-optimal for planning/training of several interventions. METHODS: In this work, we propose a strategy to construct a patient-specific atrial model...
September 8, 2017: Medical Physics
https://www.readbyqxmd.com/read/28755660/computational-and-experimental-assessment-of-influences-of-hemodynamic-shear-stress-on-carotid-plaque
#3
Hui Zhou, Long Meng, Wei Zhou, Lin Xin, Xiangxiang Xia, Shuai Li, Hairong Zheng, Lili Niu
BACKGROUND: Studies have identified hemodynamic shear stress as an important determinant of endothelial function and atherosclerosis. In this study, we assess the influences of hemodynamic shear stress on carotid plaques. METHODS: Carotid stenosis phantoms with three severity (30, 50, 70%) were made from 10% polyvinyl alcohol (PVA) cryogel. The phantoms were placed in a pulsatile flow loop with the same systolic/diastolic phase (35/65) and inlet flow rate (16 L/h)...
July 29, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28728780/detecting-regional-stiffness-changes-in-aortic-aneurysmal-geometries-using-pressure-normalized-strain
#4
Doran S Mix, Ling Yang, Camille C Johnson, Nathan Couper, Ben Zarras, Isaac Arabadjis, Lauren E Trakimas, Michael C Stoner, Steven W Day, Michael S Richards
Transabdominal ultrasound elasticity imaging could improve the assessment of rupture risk for abdominal aortic aneurysms by providing information on the mechanical properties and stress or strain states of vessel walls. We implemented a non-rigid image registration method to visualize the pressure-normalized strain within vascular tissues and adapted it to measure total strain over an entire cardiac cycle. We validated the algorithm's performance with both simulated ultrasound images with known principal strains and anatomically accurate heterogeneous polyvinyl alcohol cryogel vessel phantoms...
October 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28436134/measurement-of-skin-surface-dose-distributions-in-radiation-therapy-using-poly-vinyl-alcohol-cryogel-dosimeters
#5
Molham M Eyadeh, Marcin Wierzbicki, Kevin R Diamond
In external beam radiation therapy (EBRT), skin dose measurement is important to evaluate dose coverage of superficial target volumes. Treatment planning systems (TPSs) are often inaccurate in this region of the patient, so in vivo measurements are necessary for skin surface dose estimation. In this work, superficial dose distributions were measured using radiochromic translucent poly(vinyl alcohol) cryogels. The cryogels simultaneously served as bolus material, providing the necessary buildup to achieve the desired superficial dose...
April 24, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28331886/effects-of-line-fiducial-parameters-and-beamforming-on-ultrasound-calibration
#6
Golafsoun Ameri, John S H Baxter, A Jonathan McLeod, Terry M Peters, Elvis C S Chen
Ultrasound (US)-guided interventions are often enhanced via integration with an augmented reality environment, a necessary component of which is US calibration. Calibration requires the segmentation of fiducials, i.e., a phantom, in US images. Fiducial localization error (FLE) can decrease US calibration accuracy, which fundamentally affects the total accuracy of the interventional guidance system. Here, we investigate the effects of US image reconstruction techniques as well as phantom material and geometry on US calibration...
January 2017: Journal of Medical Imaging
https://www.readbyqxmd.com/read/28297458/translucent-poly-vinyl-alcohol-cryogel-dosimeters-for-simultaneous-dose-buildup-and-monitoring-during-chest-wall-radiation-therapy
#7
Molham M Eyadeh, Mark A Weston, Janos Juhasz, Kevin R Diamond
Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ±2,±3, and ±5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath-hold...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28114013/wall-less-flow-phantoms-with-tortuous-vascular-geometries-design-principles-and-a-patient-specific-model-fabrication-example
#8
Chung Kit Ho, Adrian J Y Chee, Billy Y S Yiu, Anderson C O Tsang, Kwok Wing Chow, Alfred C H Yu
Flow phantoms with anatomically realistic geometry and high acoustic compatibility are valuable investigative tools in vascular ultrasound studies. Here, we present a new framework to fabricate ultrasound-compatible flow phantoms to replicate human vasculature that is tortuous, non-planar and branching in nature. This framework is based upon the integration of rapid prototyping and investment casting principles. A pedagogical walkthrough of our engineering protocol is presented in this paper using a patient-specific cerebral aneurysm model as an exemplar demonstration...
December 6, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27959808/wall-less-flow-phantoms-with-tortuous-vascular-geometries-design-principles-and-a-patient-specific-model-fabrication-example
#9
Chung Kit Ho, Adrian J Y Chee, Billy Y S Yiu, Anderson C O Tsang, Kwok Wing Chow, Alfred C H Yu
Flow phantoms with anatomically realistic geometry and high acoustic compatibility are valuable investigative tools in vascular ultrasound studies. Here, we present a new framework to fabricate ultrasound-compatible flow phantoms to replicate human vasculature that is tortuous, nonplanar, and branching in nature. This framework is based upon the integration of rapid prototyping and investment casting principles. A pedagogical walkthrough of our engineering protocol is presented in this paper using a patient-specific cerebral aneurysm model as an exemplar demonstration...
January 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27685110/translucent-poly-vinyl-alcohol-cryogel-dosimeters-for-simultaneous-dose-buildup-and-monitoring-during-chest-wall-radiation-therapy
#10
Molham M Eyadeh, Mark A Weston, Janos Juhasz, Kevin R Diamond
Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ± 2, ± 3, and ± 5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath-hold...
September 8, 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/27300107/an-automatic-differentiation-based-gradient-method-for-inversion-of-the-shear-wave-equation-in-magnetic-resonance-elastography-specific-application-in-fibrous-soft-tissues
#11
Simon Chatelin, Isabelle Charpentier, Nadège Corbin, Laurence Meylheuc, Jonathan Vappou
Quantitative and accurate measurement of in vivo mechanical properties using dynamic elastography has been the scope of many research efforts over the past two decades. Most of the shear-wave-based inverse approaches for magnetic resonance elastography (MRE) make the assumption of isotropic viscoelasticity. In this paper, we propose a quantitative gradient method for inversion of the shear wave equation in anisotropic media derived from a full waveform description using analytical viscoelastic Green formalism and automatic differentiation...
July 7, 2016: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/26952900/contactless-remote-induction-of-shear-waves-in-soft-tissues-using-a-transcranial-magnetic-stimulation-device
#12
Pol Grasland-Mongrain, Erika Miller-Jolicoeur, An Tang, Stefan Catheline, Guy Cloutier
This study presents the first observation of shear waves induced remotely within soft tissues. It was performed through the combination of a transcranial magnetic stimulation device and a permanent magnet. A physical model based on Maxwell and Navier equations was developed. Experiments were performed on a cryogel phantom and a chicken breast sample. Using an ultrafast ultrasound scanner, shear waves of respective amplitudes of 5 and 0.5 μm were observed. Experimental and numerical results were in good agreement...
March 21, 2016: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/26773791/high-frame-rate-and-high-line-density-ultrasound-imaging-for-local-pulse-wave-velocity-estimation-using-motion-matching-a-feasibility-study-on-vessel-phantoms
#13
Fubing Li, Qiong He, Chengwu Huang, Ke Liu, Jinhua Shao, Jianwen Luo
Pulse wave imaging (PWI) is an ultrasound-based method to visualize the propagation of pulse wave and to quantitatively estimate regional pulse wave velocity (PWV) of the arteries within the imaging field of view (FOV). To guarantee the reliability of PWV measurement, high frame rate imaging is required, which can be achieved by reducing the line density of ultrasound imaging or transmitting plane wave at the expense of spatial resolution and/or signal-to-noise ratio (SNR). In this study, a composite, full-view imaging method using motion matching was proposed with both high temporal and spatial resolution...
April 2016: Ultrasonics
https://www.readbyqxmd.com/read/26736851/a-wall-less-poly-vinyl-alcohol-cryogel-flow-phantom-with-accurate-scattering-properties-for-transcranial-doppler-ultrasound-propagation-channels-analysis
#14
Alexander J Weir, Robin Sayer, Cheng-Xiang Wang, Stuart Parks
Medical phantoms are frequently required to verify image and signal processing systems, and are often used to support algorithm development for a wide range of imaging and blood flow assessments. A phantom with accurate scattering properties is a crucial requirement when assessing the effects of multi-path propagation channels during the development of complex signal processing techniques for Transcranial Doppler (TCD) ultrasound. The simulation of physiological blood flow in a phantom with tissue and blood equivalence can be achieved using a variety of techniques...
August 2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26030659/new-generation-laser-lithographed-dual-axis-magnetically-assisted-remote-controlled-endovascular-catheter-for-interventional-mr-imaging-in-vitro-multiplanar-navigation-at-1-5-t-and-3-t-versus-x-ray-fluoroscopy
#15
COMPARATIVE STUDY
Parham Moftakhar, Prasheel Lillaney, Aaron D Losey, Daniel L Cooke, Alastair J Martin, Bradford R H Thorne, Ronald L Arenson, Maythem Saeed, Mark W Wilson, Steven W Hetts
PURPOSE: To assess the feasibility of multiplanar vascular navigation with a new magnetically assisted remote-controlled (MARC) catheter with real-time magnetic resonance (MR) imaging at 1.5 T and 3 T and to compare it with standard x-ray guidance in simulated endovascular catheterization procedures. MATERIALS AND METHODS: A 1.6-mm-diameter custom clinical-grade microcatheter prototype with lithographed double-saddle coils at the distal tip was deflected with real-time MR imaging...
December 2015: Radiology
https://www.readbyqxmd.com/read/25350315/anisotropic-polyvinyl-alcohol-hydrogel-phantom-for-shear-wave-elastography-in-fibrous-biological-soft-tissue-a-multimodality-characterization
#16
Simon Chatelin, Miguel Bernal, Thomas Deffieux, Clément Papadacci, Patrice Flaud, Amir Nahas, Claude Boccara, Jean-Luc Gennisson, Mickael Tanter, Mathieu Pernot
Shear wave elastography imaging techniques provide quantitative measurement of soft tissues elastic properties. Tendons, muscles and cerebral tissues are composed of fibers, which induce a strong anisotropic effect on the mechanical behavior. Currently, these tissues cannot be accurately represented by existing elastography phantoms. Recently, a novel approach for orthotropic hydrogel mimicking soft tissues has been developed (Millon et al 2006 J. Biomed. Mater. Res. B 305-11). The mechanical anisotropy is induced in a polyvinyl alcohol (PVA) cryogel by stretching the physical crosslinks of the polymeric chains while undergoing freeze/thaw cycles...
November 21, 2014: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/24801192/pulsatile-flow-characterization-in-a-vessel-phantom-with-elastic-wall-using-ultrasonic-particle-image-velocimetry-technique-the-impact-of-vessel-stiffness-on-flow-dynamics
#17
Ming Qian, Lili Niu, Kelvin Kian Loong Wong, Derek Abbott, Qifa Zhou, Hairong Zheng
This study aims to experimentally investigate the impact of vessel stiffness on the flow dynamics of pulsatile vascular flow. Vessel phantoms with elastic walls were fabricated using polyvinyl alcohol cryogel to result in stiffness ranging from 60.9 to 310.3 kPa and tested with pulsatile flows using a flow circulation set-up. Two-dimensional instantaneous and time-dependent flow velocity and shear rate vector fields were measured using ultrasonic particle image velocimetry (EchoPIV). The waveforms of peak velocities measured by EchoPIV were compared with the ultrasonic pulse Doppler spectrum, and the measuring accuracy was validated...
September 2014: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/24533872/magnetically-assisted-remote-controlled-endovascular-catheter-for-interventional-mr-imaging-in-vitro-navigation-at-1-5-t-versus-x-ray-fluoroscopy
#18
Aaron D Losey, Prasheel Lillaney, Alastair J Martin, Daniel L Cooke, Mark W Wilson, Bradford R H Thorne, Ryan S Sincic, Ronald L Arenson, Maythem Saeed, Steven W Hetts
PURPOSE: To compare in vitro navigation of a magnetically assisted remote-controlled (MARC) catheter under real-time magnetic resonance (MR) imaging with manual navigation under MR imaging and standard x-ray guidance in endovascular catheterization procedures in an abdominal aortic phantom. MATERIALS AND METHODS: The 2-mm-diameter custom clinical-grade microcatheter prototype with a solenoid coil at the distal tip was deflected with a foot pedal actuator used to deliver 300 mA of positive or negative current...
June 2014: Radiology
https://www.readbyqxmd.com/read/24495438/endovascular-shear-strain-elastography-for-the-detection-and-characterization-of-the-severity-of-atherosclerotic-plaques-in-vitro-validation-and-in-vivo-evaluation
#19
Younes Majdouline, Jacques Ohayon, Zahra Keshavarz-Motamed, Marie-Hélène Roy Cardinal, Damien Garcia, Louise Allard, Sophie Lerouge, Frédéric Arsenault, Gilles Soulez, Guy Cloutier
This work explores the potential of shear strain elastograms to identify vulnerable atherosclerotic plaques. The Lagrangian speckle model estimator (LSME) elasticity imaging method was further developed to estimate shear strain elasticity (SSE). Three polyvinyl alcohol cryogel vessel phantoms were imaged with an intravascular ultrasound (IVUS) scanner. The estimated SSE maps were validated against finite-element results. Atherosclerosis was induced in carotid arteries of eight Sinclair mini-pigs using a combination of surgical techniques, diabetes and a high-fat diet...
May 2014: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/24210861/shear-wave-elastography-assessment-of-carotid-plaque-stiffness-in%C3%A2-vitro-reproducibility-study
#20
Kumar V Ramnarine, James W Garrard, Katie Dexter, Sarah Nduwayo, Ronney B Panerai, Thompson G Robinson
This study assessed inter- and intra-observer reproducibility of shear wave elastography (SWE) measurements in vessel phantoms simulating soft and hard carotid plaque under steady and pulsatile flow conditions. Supersonic SWE was used to acquire cine-loop data and quantify Young's modulus in cryogel vessel phantoms. Data were acquired by two observers, each performing three repeat measurements. Mean Young's modulus was quantified within 2-mm regions of interest averaged across five frames and, depending on vessel model and observer, ranged from 28 to 240 kPa...
January 2014: Ultrasound in Medicine & Biology
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