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https://www.readbyqxmd.com/read/28436134/measurement-of-skin-surface-dose-distributions-in-radiation-therapy-using-poly-vinyl-alcohol-cryogel-dosimeters
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
https://www.readbyqxmd.com/read/24134700/producing-homogeneous-cryogel-phantoms-for-medical-imaging-a-finite-element-approach
#17
Amin Iravani, Jens Mueller, Azizeh-Mitra Yousefi
Tissue-mimicking phantoms with well-defined properties can help in identifying the potential weaknesses in medical imaging systems. Among the imaging systems, magnetic resonance elastography is a new noninvasive technique used to quantify the shear modulus of biological tissues, and therefore has shown promise in studying liver and brain pathologies. Polyvinyl alcohol (PVA) cryogel prepared by the freeze-thaw technique is a potential candidate for mimicking the mechanical properties of soft tissues and has been extensively used as a phantom material...
2014: Journal of Biomaterials Science. Polymer Edition
https://www.readbyqxmd.com/read/23366603/a-biventricular-multimodal-mri-ultrasound-cardiac-phantom
#18
Vahid Tavakoli, M J Negahdar, Michael Kendrick, Motaz Alshaher, Marcus Stoddard, Amir A Amini
A cardiac phantom can be of crucial importance in the development and validation of ultrasound and cardiac magnetic resonance (MR) imaging and image analysis methods. A biventricular multimodal cardiac phantom has been manufactured in-house that can simulate normal and pathologic hearts with different degrees of infarction. The two-chamber structure can simulate the asymmetric left ventricular motion. Poly Vinyl Alcohol (PVA) is utilized as the basic material since it can simulate the shape, elasticity, and MR and ultrasound properties of the heart...
2012: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/23130805/improving-the-homogeneity-of-tissue-mimicking-cryogel-phantoms-for-medical-imaging
#19
Joshua A Minton, Amin Iravani, Azizeh-Mitra Yousefi
PURPOSE: Tissue-mimicking phantoms can help in uncovering potential weaknesses in medical imaging systems. This work presents a new approach to developing phantoms for magnetic resonance elastography (MRE). Elastography requires sufficiently large and well-characterized phantoms to accurately validate motion estimation methods and to provide accurate stiffness measurements. Physically crosslinked polyvinyl alcohol hydrogels, prepared by the freeze-thaw technique, have been extensively used as MRE phantoms...
November 2012: Medical Physics
https://www.readbyqxmd.com/read/22770689/development-and-characterization-of-rodent-cardiac-phantoms-comparison-with-in-vivo-cardiac-imaging
#20
COMPARATIVE STUDY
Steven Fortune, Maurits A Jansen, Tom Anderson, Gillian A Gray, Jürgen E Schneider, Peter R Hoskins, Ian Marshall
The increasing availability of rodent models of human cardiovascular disease has led to a need to translate noninvasive imaging techniques such as magnetic resonance imaging (MRI) from the clinic to the animal laboratory. The aim of this study was to develop phantoms simulating the short-axis view of left ventricular motion of rats and mice, thus reducing the need for live animals in the development of MRI. Cylindrical phantoms were moulded from polyvinyl alcohol (PVA) Cryogel and attached via stiff water-filled tubing to a gear pump...
October 2012: Magnetic Resonance Imaging
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