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https://www.readbyqxmd.com/read/28644905/a-realistic-phantom-for-validating-mri-based-synthetic-ct-images-of-the-human-skull
#1
Abraam S Soliman, Levi Burns, Amir Owrangi, Young Lee, William Y Song, Greg Stanisz, Brige P Chugh
PURPOSE: To introduce a new realistic human skull phantom for the validation of synthetic CT images of cortical bone from ultra-short echo-time (UTE) sequences. METHODS AND MATERIALS: A human skull of an adult female was utilized as a realistic representation of skull cortical bone. The skull was stabilized in a special acrylic container and was filled with contrast agents that have T1 and T2 relaxation times similar to human brain. The phantom was MR scanned at 3T with UTE and T2 -weighted sequences, followed by CT...
June 23, 2017: Medical Physics
https://www.readbyqxmd.com/read/28644819/quantifying-the-accuracy-and-precision-of-a-novel-real-time-6-degree-of-freedom-kilovoltage-intrafraction-monitoring-kim-target-tracking-system
#2
J-H Kim, D T Nguyen, C-Y Huang, T Fuangrod, V Caillet, R O'Brien, P Poulsen, J Booth, P Keall
Target rotation can considerably impact the delivered radiotherapy dose depending on the tumour shape. More accurate tumour pose during radiotherapy treatment can be acquired through tracking in 6 degrees-of-freedom (6 DoF) rather than in translation only. A novel real-time 6 DoF kilovoltage intrafraction monitoring (KIM) target tracking system has recently been developed. In this study, we experimentally evaluated the accuracy and precision of the 6 DoF KIM implementation. Real-time 6 DoF KIM motion measurements were compared against the ground truth motion retrospectively derived from kV/MV triangulation for a range of lung and prostate tumour motion trajectories as well as for various static poses using a phantom...
June 23, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28644804/global-time-delay-estimation-in-ultrasound-elastography
#3
Hoda S Hashemi, Hassan Rivaz
A critical step in quasi-static ultrasound elastography is estimation of time-delay between two frames of radiofrequency (RF) data that are obtained while the tissue is undergoing deformation. This paper presents a novel technique for timedelay estimation (TDE) of all samples of RF data simultaneously, thereby exploiting all the information in RF data for TDE. A nonlinear cost function that incorporates similarity of RF data intensity and prior information of displacement continuity is formulated. Optimization of this function involves searching for TDE of all samples of the RF data, rendering the optimization intractable with conventional techniques given that the number of variables can be approximately one million...
June 21, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28644801/magnetic-particle-imaging-for-quantification-of-vascular-stenoses-a-phantom-study
#4
S Herz, P Vogel, T Kampf, M A Ruckert, S Veldhoen, V C Behr, T A Bley
Magnetic particle imaging (MPI) is a promising new tomographic imaging method to detect the spatial distribution of superparamagnetic iron-oxide nanoparticles (SPIOs). The aim of this study was to investigate the potential of MPI to quantify artificial stenoses in vessel phantoms. Custom-made stenosis phantoms (length 40 mm; inner diameter 8 mm) with different degrees of stenosis (0 %, 25 %, 50 %, 75 % and 100 %) were scanned in a custom-built MPI scanner (in-plane resolution: ~ 1-1.5 mm, field of view: 65 × 29 × 29 mm3)...
June 21, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28644800/online-combination-of-epid-cherenkov-imaging-for-3d-dosimetry-in-a-liquid-phantom
#5
Petr Bruza, Jacqueline M Andreozzi, David J Gladstone, Lesley A Jarvis, Joerg Rottmann, Brian W Pogue
Online acquisition of Cherenkov and portal imaging data was combined with a reconstruction scheme called EC3D, providing a full 3D dosimetry of megavoltage X-ray beams in a water tank. The methodology was demonstrated and quantified in a single static beam. Furthermore, the dynamics and visualization of the 3D dose reconstruction were demonstrated with a volumetric modulated arc therapy (VMAT) plan for TG-119 C-Shape geometry. The developed algorithm combines depth dose information, provided by Cherenkov images, with the lateral dose distribution, provided by the electronic portal imaging device (EPID)...
June 20, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28644152/incorporating-hypr-de-noising-within-iterative-pet-reconstruction-hypr-osem
#6
Ju-Chieh Kevin Cheng, Julian C Matthews, Vesna Sossi, Jose Anton-Rodriguez, Andre Salomon, Ronald Boellaard
HighlY constrained back-PRojection (HYPR) is a post-processing de-noising technique originally developed for time-resolved Magnetic Resonance Imaging. It has been recently applied to dynamic imaging for Positron Emission Tomography (PET) and shown promising results. In this work, we have developed an iterative reconstruction algorithm (HYPR-OSEM) which improves the signal-to-noise ratio (SNR) in static imaging (i.e. single frame reconstruction) by incorporating HYPR de-noising directly within the ordered subsets expectation maximization (OSEM) algorithm...
June 23, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28643752/dosimetric-characterization-of-optically-stimulated-luminescence-dosimeter-with-therapeutic-photon-beams-for-use-in-clinical-radiotherapy-measurements
#7
Retna Ponmalar, Ravikumar Manickam, K M Ganesh, Sathiyan Saminathan, Arun Raman, Henry Finlay Godson
AIM: The modern radiotherapy techniques impose new challenges for dosimetry systems with high precision and accuracy in in vivo and in phantom dosimetric measurements. The knowledge of the basic characterization of a dosimetric system before patient dose verification is crucial. This incites the investigation of the potential use of nanoDot optically stimulated luminescence dosimeter (OSLD) for application in radiotherapy with therapeutic photon beams. MATERIALS AND METHODS: Measurements were carried out with nanoDot OSLDs to evaluate the dosimetric characteristics such as dose linearity, dependency on field size, dose rate, energy and source-to-surface distance (SSD), reproducibility, fading effect, reader stability, and signal depletion per read out with cobalt-60 (60 Co) beam, 6 and 18 MV therapeutic photon beams...
April 2017: Journal of Cancer Research and Therapeutics
https://www.readbyqxmd.com/read/28643408/the-effect-of-concomitant-fields-in-fast-spin-echo-acquisition-on-asymmetric-mri-gradient-systems
#8
Shengzhen Tao, Paul T Weavers, Joshua D Trzasko, John Huston, Yunhong Shu, Erin M Gray, Thomas K F Foo, Matt A Bernstein
PURPOSE: To investigate the effect of the asymmetric gradient concomitant fields (CF) with zeroth and first-order spatial dependence on fast/turbo spin-echo acquisitions, and to demonstrate the effectiveness of their real-time compensation. METHODS: After briefly reviewing the CF produced by asymmetric gradients, the effects of the additional zeroth and first-order CFs on these systems are investigated using extended-phase graph simulations. Phantom and in vivo experiments are performed to corroborate the simulation...
June 22, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28643383/multiecho-pseudo-golden-angle-stack-of-stars-thermometry-with-high-spatial-and-temporal-resolution-using-k-space-weighted-image-contrast
#9
Bryant T Svedin, Allison Payne, Bradley D Bolster, Dennis L Parker
PURPOSE: Implement and evaluate a 3D MRI method to measure temperature changes with high spatial and temporal resolution and large field of view. METHODS: A multiecho pseudo-golden angle stack-of-stars (SOS) sequence with k-space weighted image contrast (KWIC) reconstruction was implemented to simultaneously measure multiple quantities, including temperature, initial signal magnitude M(0), transverse relaxation time ( T2*), and water/fat images. Respiration artifacts were corrected using self-navigation...
June 22, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28643118/comparison-of-photon-organ-and-effective-dose-coefficients-for-pimal-stylized-phantom-in-bent-positions-in-standard-irradiation-geometries
#10
Shaheen Dewji, K Lisa Reed, Mauritius Hiller
Computational phantoms with articulated arms and legs have been constructed to enable the estimation of radiation dose in different postures. Through a graphical user interface, the Phantom wIth Moving Arms and Legs (PIMAL) version 4.1.0 software can be employed to articulate the posture of a phantom and generate a corresponding input deck for the Monte Carlo N-Particle (MCNP) radiation transport code. In this work, photon fluence-to-dose coefficients were computed using PIMAL to compare organ and effective doses for a stylized phantom in the standard upright position with those for phantoms in realistic work postures...
June 22, 2017: Radiation and Environmental Biophysics
https://www.readbyqxmd.com/read/28643059/the-learning-effect-of-using-stereoscopic-vision-in-the-early-phase-of-laparoscopic-surgical-training-for-novices
#11
Hitoshi Harada, Shingo Kanaji, Masayasu Nishi, Yoshito Otake, Hiroshi Hasegawa, Masashi Yamamoto, Yoshiko Matsuda, Kimihiro Yamashita, Takeru Matsuda, Taro Oshikiri, Yasuo Sumi, Tetsu Nakamura, Satoshi Suzuki, Yoshinobu Sato, Yoshihiro Kakeji
BACKGROUND: Recently to improve depth perception, the performance of three-dimensional (3D) laparoscopic surgeries has increased. However, the effects of laparoscopic training using 3D are still unclear. This study aimed to clarify the effects of using a 3D monitor among novices in the early phase of training. METHODS: Participants were 40 novices who had never performed laparoscopic surgery (20 medical students and 20 junior residents). Three laparoscopic phantom tasks (task 1: touching markers on a flat disk with a rod; task 2: straight rod transfer through a single loop; and task 3: curved rod transfer through two loops) in the training box were performed ten times, respectively...
June 22, 2017: Surgical Endoscopy
https://www.readbyqxmd.com/read/28643024/automatic-seed-picking-for-brachytherapy-postimplant-validation-with-3d-ct-images
#12
Guobin Zhang, Qiyuan Sun, Shan Jiang, Zhiyong Yang, Xiaodong Ma, Haisong Jiang
PURPOSE: Postimplant validation is an indispensable part in the brachytherapy technique. It provides the necessary feedback to ensure the quality of operation. The ability to pick implanted seed relates directly to the accuracy of validation. To address it, an automatic approach is proposed for picking implanted brachytherapy seeds in 3D CT images. METHODS: In order to pick seed configuration (location and orientation) efficiently, the approach starts with the segmentation of seed from CT images using a thresholding filter which based on gray-level histogram...
June 22, 2017: International Journal of Computer Assisted Radiology and Surgery
https://www.readbyqxmd.com/read/28642854/measurement-uncertainty-in-spine-bone-mineral-density-by-dual-energy-x-ray-absorptiometry
#13
Ae-Ja Park, Jun-Il Yoo, Jee-Hye Choi, Kyun Shik Chae, Chang Geun Kim, Dal Sik Kim
BACKGROUND: The purpose of this study was to calculate the measurement uncertainty of the process of bone mineral density (BMD) analysis using dual energy X-ray absorptiometry with traceability. METHODS: Between March 2015 and October 2016, among healthy participants in their 20s and 30s, the study included those who had not taken calcium, vitamin D supplements and steroids and were without a history of osteoporosis, osteopenia and diseases related to osteoporosis...
May 2017: Journal of Bone Metabolism
https://www.readbyqxmd.com/read/28642054/development-of-a-tailored-thyroid-gland-phantom-for-fine-needle-aspiration-cytology-by-three-dimensional-printing
#14
Masayuki Baba, Keitaro Matsumoto, Naoya Yamasaki, Hisakazu Shindo, Hiroshi Yano, Megumi Matsumoto, Ryota Otsubo, Murray John Lawn, Naoto Matsuo, Ikuo Yamamoto, Shigekazu Hidaka, Takeshi Nagayasu
BACKGROUND: Fine-needle aspiration cytology (FNAC) is a challenging and risky procedure for inexperienced clinicians to perform because of the proximity of the thyroid to the jugular veins, carotid arteries, and trachea. A phantom model for transfixion practice would help train clinicians in FNAC. OBJECTIVE: To fabricate a tailored phantom with consideration for authenticity of size, touch, feel, and ultrasonographic (US) characteristics. METHODS: A three-dimensional (3D) digital model of the human neck was reconstructed from computed tomography data of a subject...
June 19, 2017: Journal of Surgical Education
https://www.readbyqxmd.com/read/28641910/dependence-of-boiling-histotripsy-treatment-efficiency-on-hifu-frequency-and-focal-pressure-levels
#15
Tatiana D Khokhlova, Yasser A Haider, Adam D Maxwell, Wayne Kreider, Michael R Bailey, Vera A Khokhlova
Boiling histotripsy (BH) is a high-intensity focused ultrasound (HIFU)-based method of mechanical tissue fractionation that utilizes millisecond-long bursts of HIFU shock waves to cause boiling at the focus in milliseconds. The subsequent interaction of the incoming shocks with the vapor bubble mechanically lyses surrounding tissue and cells. The acoustic parameter space for BH has been investigated previously and an inverse dependence between the HIFU frequency and the dimensions of a BH lesion has been observed...
June 19, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28641250/deep-convolutional-neural-network-for-inverse-problems-in-imaging
#16
Kyong Hwan Jin, Michael T McCann, Emmanuel Froustey, Michael Unser
In this paper, we propose a novel deep convolutional neural network (CNN)-based algorithm for solving ill-posed inverse problems. Regularized iterative algorithms have emerged as the standard approach to ill-posed inverse problems in the past few decades. These methods produce excellent results, but can be challenging to deploy in practice due to factors including the high computational cost of the forward and adjoint operators and the difficulty of hyper parameter selection. The starting point of our work is the observation that unrolled iterative methods have the form of a CNN (filtering followed by point-wise nonlinearity) when the normal operator ( H*H where H* is the adjoint of the forward imaging operator, H ) of the forward model is a convolution...
June 15, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28641249/eit-imaging-regularization-based-on-spectral-graph-wavelets
#17
Bo Gong, Benjamin Schullcke, Sabine Krueger-Ziolek, Marko Vauhkonen, Gerhard Wolf, Ullrich Mueller-Lisse, Knut Moeller
The objective of Electrical Impedance Tomographic reconstruction is to identify the distribution of tissue conductivity from electrical boundary conditions. This is an ill-posed inverse problem usually solved under the finite element method framework. In previous studies, standard sparse regularization was used for difference EIT to achieve a sparse solution. However, regarding element-wise sparsity, standard sparse regularization interferes with the smoothness of conductivity distribution between neighboring elements and is sensitive to noise...
June 16, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28640950/development-of-a-monte-carlo-multiple-source-model-for-inclusion-in-a-dose-calculation-auditing-tool
#18
Austin M Faught, Scott E Davidson, Jonas Fontenot, Stephen F Kry, Carol Etzel, Geoffrey S Ibbott, David S Followill
PURPOSE: The Imaging and Radiation Oncology Core Houston (IROC-H) (formerly the Radiological Physics Center) has reported varying levels of agreement in their anthropomorphic phantom audits. There is reason to believe one source of error in this observed disagreement is the accuracy of the dose calculation algorithms and heterogeneity corrections used. To audit this component of the radiotherapy treatment process an independent dose calculation tool is needed. METHODS: Monte Carlo multiple source models for Elekta 6MV and 10MV therapeutic x-ray beams were commissioned based on measurement of central axis depth dose data for a 10 x 10 cm(2) field size and dose profiles for a 40 x 40 cm(2) field size...
June 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28640923/how-much-detail-is-needed-in-modeling-a-transcranial-magnetic-stimulation-figure-8-coil-measurements-and-brain-simulations
#19
Petar I Petrov, Stefano Mandija, Iris E C Sommer, Cornelis A T van den Berg, Sebastiaan F W Neggers
BACKGROUND: Despite TMS wide adoption, its spatial and temporal patterns of neuronal effects are not well understood. Although progress has been made in predicting induced currents in the brain using realistic finite element models (FEM), there is little consensus on how a magnetic field of a typical TMS coil should be modeled. Empirical validation of such models is limited and subject to several limitations. METHODS: We evaluate and empirically validate models of a figure-of-eight TMS coil that are commonly used in published modeling studies, of increasing complexity: simple circular coil model; coil with in-plane spiral winding turns; and finally one with stacked spiral winding turns...
2017: PloS One
https://www.readbyqxmd.com/read/28640198/experimental-investigation-of-magnetic-nanoparticle-enhanced-microwave-hyperthermia
#20
Brogan T McWilliams, Hongwang Wang, Valerie J Binns, Sergio Curto, Stefan H Bossmann, Punit Prakash
The objective of this study was to evaluate microwave heating enhancements offered by iron/iron oxide nanoparticles dispersed within tissue-mimicking media for improving efficacy of microwave thermal therapy. The following dopamine-coated magnetic nanoparticles (MNPs) were considered: 10 and 20 nm diameter spherical core/shell Fe/Fe₃O₄, 20 nm edge-length cubic Fe₃O₄, and 45 nm edge-length/10 nm height hexagonal Fe₃O₄. Microwave heating enhancements were experimentally measured with MNPs dissolved in an agar phantom, placed within a rectangular waveguide...
June 22, 2017: Journal of Functional Biomaterials
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