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https://www.readbyqxmd.com/read/28324943/overcoming-spatio-temporal-limitations-using-dynamically-scaled-in-vitro-pc-mri-a-flow-field-comparison-to-true-scale-computer-simulations-of-idealized-stented-and-patient-specific-left-main-bifurcations
#1
Susann Beier, John Ormiston, Mark Webster, John Cater, Stuart Norris, Pau Medrano-Gracia, Alistair Young, Kathleen Gilbert, Brett Cowan
The majority of patients with angina or heart failure have coronary artery disease. Left main bifurcations are particularly susceptible to pathological narrowing. Flow is a major factor of atheroma development, but limitations in imaging technology such as spatio-temporal resolution, signal-to-noise ratio (SNRv), and imaging artefacts prevent in vivo investigations. Computational fluid dynamics (CFD) modelling is a common numerical approach to study flow, but it requires a cautious and rigorous application for meaningful results...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28324122/mr-imaging-differentiation-of-fe-2-and-fe-3-based-on-relaxation-and-magnetic-susceptibility-properties
#2
Olaf Dietrich, Johannes Levin, Seyed-Ahmad Ahmadi, Annika Plate, Maximilian F Reiser, Kai Bötzel, Armin Giese, Birgit Ertl-Wagner
PURPOSE: The aim of this study is to evaluate the MR imaging behavior of ferrous (Fe(2+)) and ferric (Fe(3+)) iron ions in order to develop a noninvasive technique to quantitatively differentiate between both forms of iron. METHODS: MRI was performed at 3 T in a phantom consisting of 21 samples with different concentrations of ferrous and ferric chloride solutions (between 0 and 10 mmol/L). A multi-echo spoiled gradient-echo pulse sequence with eight echoes was used for both T 2* and quantitative susceptibility measurements...
March 21, 2017: Neuroradiology
https://www.readbyqxmd.com/read/28323633/rotational-magneto-acousto-electric-tomography-maet-theory-and-experimental-validation
#3
L Kunyansky, C P Ingram, R S Witte
We present a novel two-dimensional (2D) MAET scanner, with a rotating object of interest and two fixed pairs of electrodes. Such an acquisition scheme, with our novel reconstruction techniques, recovers the boundaries of the regions of constant conductivity uniformly well, regardless of their orientation. We also present a general image reconstruction algorithm for the 2D MAET in a circular chamber with point-like electrodes immersed into the saline surrounding the object. An alternative linearized reconstruction procedure is developed, suitable for recovering the material interfaces (boundaries) when a non-ideal piezoelectric transducer is used for acoustic excitation...
March 21, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28319031/evaluation-of-the-water-equivalence-of-plastic-materials-in-low-and-high-energy-clinical-proton-beams
#4
Ana Lourenco, David Shipley, Nigel Wellock, Russell Thomas, Hugo Bouchard, Andrzej Kacperek, Francesco Fracchiolla, Stefano Lorentini, Marco Schwarz, Niall MacDougall, Gary Royle, Hugo Palmans
The aim of this work was to evaluate the water-equivalence of new trial plastics designed specifically for light-ion beam dosimetry as well as commercially available plastics in clinical proton beams. The water-equivalence of materials was tested by computing a plastic-to-water conversion factor, <i>H</i><sub><i>pl</i>,w</sub>. Trial materials were characterized experimentally in 60 MeV and 226 MeV un-modulated proton beams and the results were compared with Monte Carlo simulations using the FLUKA code...
March 20, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28318888/characterization-of-the-lung-parenchyma-using-ultrasound-multiple-scattering
#5
Kaustav Mohanty, John Blackwell, Thomas Egan, Marie Muller
The purpose of the study described here was to showcase the application of ultrasound to quantitative characterization of the micro-architecture of the lung parenchyma to predict the extent of pulmonary edema. The lung parenchyma is a highly complex and diffusive medium for which ultrasound techniques have remained qualitative. The approach presented here is based on ultrasound multiple scattering and exploits the complexity of ultrasound propagation in the lung structure. The experimental setup consisted of a linear transducer array with an 8-MHz central frequency placed in contact with the lung surface...
March 16, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28318887/multi-focus-beamforming-for-thermal-strain-imaging-using-a-single-ultrasound-linear-array-transducer
#6
Man M Nguyen, Xuan Ding, Steven A Leers, Kang Kim
Ultrasound-induced thermal strain imaging (TSI) has been used successfully to identify lipid- and water-based tissues in atherosclerotic plaques in some research settings. However, TSI faces several challenges to be realized in clinics. These challenges include motion artifacts and displacement tracking accuracy, as well as limited heating capability, which contributes to low thermal strain signal-to-noise ratio, and a limited field of view. Our goal was to address the challenge in heating tissue in TSI. Current TSI systems use separate heating and imaging transducers, which require physical alignment of the heating and imaging beams and result in a bulky setup that limits in vivo operation...
March 15, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28318066/three-dimensional-ultrashort-echo-time-cones-t1%C3%AF-3d-ute-cones-t1%C3%AF-imaging
#7
Ya-Jun Ma, Michael Carl, Hongda Shao, Anthony S Tadros, Eric Y Chang, Jiang Du
We report a novel three-dimensional (3D) ultrashort echo time (UTE) sequence employing Cones trajectory and T1ρ preparation (UTE-Cones-T1ρ ) for quantitative T1ρ assessment of short T2 tissues in the musculoskeletal system. A basic 3D UTE-Cones sequence was combined with a spin-locking preparation pulse for T1ρ contrast. A relatively short TR was used to decrease the scan time, which required T1 measurement and compensation using 3D UTE-Cones data acquisitions with variable TRs. Another strategy to reduce the total scan time was to acquire multiple Cones spokes (Nsp ) after each T1ρ preparation and fat saturation...
March 20, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28317312/evaluation-of-dose-calculation-accuracy-of-treatment-planning-systems-at-hip-prosthesis-interfaces
#8
David Paulu, Parham Alaei
There are an increasing number of radiation therapy patients with hip prosthesis. The common method of minimizing treatment planning inaccuracies is to avoid radiation beams to transit through the prosthesis. However, the beams often exit through them, especially when the patient has a double-prosthesis. Modern treatment planning systems employ algorithms with improved dose calculation accuracies but even these algorithms may not predict the dose accurately at high atomic number interfaces. The current study evaluates the dose calculation accuracy of three common dose calculation algorithms employed in two commercial treatment planning systems...
March 20, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28317261/diffusion-relaxation-correlation-spectroscopic-imaging-a-multidimensional-approach-for-probing-microstructure
#9
Daeun Kim, Eamon K Doyle, Jessica L Wisnowski, Joong Hee Kim, Justin P Haldar
PURPOSE: To propose and evaluate a novel multidimensional approach for imaging subvoxel tissue compartments called Diffusion-Relaxation Correlation Spectroscopic Imaging. THEORY AND METHODS: Multiexponential modeling of MR diffusion or relaxation data is commonly used to infer the many different microscopic tissue compartments that contribute signal to macroscopic MR imaging voxels. However, multiexponential estimation is known to be difficult and ill-posed. Observing that this ill-posedness is theoretically reduced in higher dimensions, diffusion-relaxation correlation spectroscopic imaging uses a novel multidimensional imaging experiment that jointly encodes diffusion and relaxation information, and then uses a novel constrained reconstruction technique to generate a multidimensional diffusion-relaxation correlation spectrum for every voxel...
March 19, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28317129/towards-robust-adaptive-radiation-therapy-strategies
#10
Michelle Böck, Anders Forsgren, Kjell Eriksson, Björn Hårdemark
PURPOSE: To set up a framework combining robust treatment planning with adaptive reoptimization in order to maintain high treatment quality, to respond to interfractional geometric variations and to identify those patients who will benefit the most from an adaptive fractionation schedule. METHODS: The authors propose robust adaptive strategies based on stochastic minimax optimization for a series of simulated treatments on a one-dimensional patient phantom. The plan applied during the first fractions should be able to handle anticipated systematic and random errors...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317122/an-anthropomorphic-abdominal-phantom-for-deformable-image-registration-accuracy-validation-in-adaptive-radiation-therapy
#11
Yuliang Liao, Linjing Wang, Xiangdong Xu, Haibin Chen, Jiawei Chen, Guoqian Zhang, Huaiyu Lei, Ruihao Wang, Shuxu Zhang, Xuejun Gu, Xin Zhen, Linghong Zhou
PURPOSE: To design and construct a three-dimensional (3D) anthropomorphic abdominal phantom for geometric accuracy and dose summation accuracy evaluations of deformable image registration (DIR) algorithms for adaptive radiation therapy (ART). METHOD: Organ molds, including liver, kidney, spleen, stomach, vertebra and two metastasis tumors, were 3D printed using contours from an ovarian cancer patient. The organ molds were molded with deformable gels made of different mixtures of polyvinyl chloride (PVC) and the softener dioctyl terephthalate...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28306556/metal-artifact-reduction-in-mri-based-cervical-cancer-intracavitary-brachytherapy
#12
Yuan James Rao, Jacqueline E Zoberi, Mo Kadbi, Perry W Grigsby, Jochen Cammin, Stacie L Mackey, Jose Garcia-Ramirez, S Murty Goddu, Julie K Schwarz, H Michael Gach
Magnetic resonance imaging (MRI) plays an increasingly important role in brachytherapy planning for cervical cancer. Yet, metal tandem, ovoid intracavitary applicators, and fiducial markers used in brachytherapy cause magnetic susceptibility artifacts in standard MRI. These artifacts may impact the accuracy of brachytherapy treatment and the evaluation of tumor response by misrepresenting the size and location of the metal implant, and distorting the surrounding anatomy and tissue. Metal artifact reduction sequences (MARS) with high bandwidth RF selective excitations and turbo spin-echo readouts were developed for MRI of orthopedic implants...
March 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28306555/assessment-of-dosimetric-impact-of-system-specific-geometric-distortion-in-an-mri-only-based-radiotherapy-workflow-for-prostate
#13
C Gustafsson, F Nordström, E Persson, J Brynolfsson, L E Olsson
Dosimetric errors in a magnetic resonance imaging (MRI) only radiotherapy workflow may be caused by system specific geometric distortion from MRI. The aim of this study was to evaluate the impact on planned dose distribution and delineated structures for prostate patients, originating from this distortion. A method was developed, in which computer tomography (CT) images were distorted using the MRI distortion field. The displacement map for an optimized MRI treatment planning sequence was measured using a dedicated phantom in a 3 T MRI system...
March 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28306546/substitute-ct-generation-from-a-single-ultra-short-time-echo-mri-sequence-preliminary-study
#14
Soumya Ghose, Jason A Dowling, Robba Rai, Gary P Liney
In MR guided radiation therapy planning both MR and CT images for a patient are acquired and co-registered to obtain a tissue specific HU map. Generation of the HU map directly from the MRI would eliminate the CT acquisition and may improve radiation therapy planning. In this preliminary study of substitute CT (sCT) generation, two porcine leg phantoms were scanned using a 3D ultrashort echo time (PETRA) sequence and co-registered to corresponding CT images to build tissue specific regression models. The model was created from one co-registered CT-PETRA pair to generate the sCT for the other PETRA image...
March 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28303617/joint-system-relaxometry-jsr-and-cr%C3%A3-mer-rao-lower-bound-optimization-of-sequence-parameters-a-framework-for-enhanced-precision-of-despot-t1-and-t2-estimation
#15
Rui Pedro A G Teixeira, Shaihan J Malik, Joseph V Hajnal
PURPOSE: This study aims to increase the precision of single-compartment DESPOT relaxometry by two means: (i) a joint system relaxometry (JSR) approach that estimates parameters in a single step using all available data; and (ii) optimizing acquisition parameters by deploying a robust design tool based on the Crámer-Rao lower bound (CRLB). METHODS: Following the development of the analysis and design capabilities, phantom and four in vivo subject experiments were performed to compare directly the precision achieved with DESPOT and JSR estimation using published protocols and protocols designed using a proposed CRLB framework...
March 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28303087/a-pilot-genome-wide-association-study-identifies-potential-metabolic-pathways-involved-in-tinnitus
#16
Annick Gilles, Guy Van Camp, Paul Van de Heyning, Erik Fransen
Tinnitus, the perception of an auditory phantom sound in the form of ringing, buzzing, roaring, or hissing in the absence of an external sound source, is perceived by ~15% of the population and 2.5% experiences a severely bothersome tinnitus. The contribution of genes on the development of tinnitus is still under debate. The current manuscript reports a pilot Genome Wide Association Study (GWAS) into tinnitus, in a small cohort of 167 independent tinnitus subjects, and 749 non-tinnitus controls, who were collected as part of a cross-sectional study...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/28302761/performance-characteristics-of-the-whole-body-discovery-iq-pet-ct-system
#17
Gabriel Reynes-Llompart, Cristina Gámez-Cenzano, Inma Romero-Zayas, Laura Rodriguez-Bel, José Luís Vercher-Conejero, Josep M Martí-Climent
Purpose: The aim of this study was to assess the physical performance of a new PET/CT system Discovery IQ 5 Rings (General Electric, Milwaukee, WI). Methods: Performance measurements were obtained using the NEMA NU2-2012 methodology. Image quality was extended by accounting for different acquisition parameters (lesion-to-background ratios of 8:1, 4:1 and 2:1 and acquisition times) as well as different reconstruction algorithms (VPHD, VPHD-S and Q.Clear). Tomographic reconstruction was also assessed using a Jaszczak phantom...
March 16, 2017: Journal of Nuclear Medicine: Official Publication, Society of Nuclear Medicine
https://www.readbyqxmd.com/read/28302493/the-risk-of-second-primary-cancers-due-to-peripheral-photon-and-neutron-doses-received-during-prostate-cancer-external-beam-radiation-therapy
#18
Eva Bezak, Rundgham Takam, Eric Yeoh, Loredana G Marcu
BACKGROUND: Out-of-field organs can be affected by secondary radiations originating from high energy linear accelerators, leading to an increased risk of carcinogenesis. The aim of this work was to determine the risk of second primary cancers (SPC) in the organs distal to the prostate during 3D conformal radiotherapy. MATERIALS AND METHODS: Based on previously measured peripheral photon and neutron doses in a Rando phantom using an 18MV photon beam, SPC risks in the out-of-field organs were estimated using the linear-no-threshold and the competitive risk models...
March 13, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28301638/benchmarking-of-fluorescence-cameras-through-the-use-of-a-composite-phantom
#19
Dimitris Gorpas, Maximilian Koch, Maria Anastasopoulou, Uwe Klemm, Vasilis Ntziachristos
No abstract text is available yet for this article.
January 1, 2017: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/28301597/boiling-histotripsy-lesion-characterization-on-a-clinical-magnetic-resonance-imaging-guided-high-intensity-focused-ultrasound-system
#20
Avinash Eranki, Navid Farr, Ari Partanen, Karun V Sharma, Hong Chen, Christopher T Rossi, Satya V V N Kothapalli, Matthew Oetgen, AeRang Kim, Ayele H Negussie, David Woods, Bradford J Wood, Peter C W Kim, Pavel S Yarmolenko
PURPOSE: High intensity focused ultrasound (HIFU) is a non-invasive therapeutic technique that can thermally ablate tumors. Boiling histotripsy (BH) is a HIFU approach that can emulsify tissue in a few milliseconds. Lesion volume and temperature effects for different BH sonication parameters are currently not well characterized. In this work, lesion volume, temperature distribution, and area of lethal thermal dose were characterized for varying BH sonication parameters in tissue-mimicking phantoms (TMP) and demonstrated in ex vivo tissues...
2017: PloS One
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