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Andrea Toelly, Constanze Bardach, Michael Weber, Rui Gong, Yanbo Lai, Pei Wang, Yulin Guo, Jan Kirschke, Thomas Baum, Michael Gruber
Aim To evaluate the differences in phantom-less bone mineral density (BMD) measurements in contrast-enhanced routine MDCT scans at different contrast phases, and to develop an algorithm for calculating a reliable BMD value. Materials and Methods 112 postmenopausal women from the age of 40 to 77 years (mean age: 57.31 years; SD 9.61) who underwent a clinically indicated MDCT scan, consisting of an unenhanced, an arterial, and a venous phase, were included. A retrospective analysis of the BMD values of the Th12 to L4 vertebrae in each phase was performed using a commercially available phantom-less measurement tool...
April 26, 2017: RöFo: Fortschritte Auf Dem Gebiete der Röntgenstrahlen und der Nuklearmedizin
J Andoh, M Diers, C Milde, C Köppe, D Kleinböhl, H Flor
Previous work showed the existence of changes in the topographic organization within the somatosensory cortex (SI) in amputees with phantom limb pain, however, the link between nonpainful phantom sensations such as cramping or tingling or the percept of the limb and cortical changes is less clear. We used functional magnetic resonance imaging (fMRI) in a highly selective group of limb amputees who experienced inducible and reproducible nonpainful phantom sensations. A standardized procedure was used to locate body sites eliciting phantom sensations in each amputee...
April 23, 2017: Biological Psychology
Ian S Armstrong, Katharine E Thomson, Lisa M Rowley, Daniel R McGowan
PET iterative reconstruction algorithms with resolution modelling (RM) can be used to improve spatial resolution in the images. However, RM has a significant impact on quantification, which raises issues for harmonization across multicentre networks or collaborations. This investigation compared quantification from two modern time-of-flight (TOF) PET/CT systems from different manufacturers with RM with the intention to harmonize recovery. Images of a National Electrical Manufacturers Association image quality phantom with a sphere-to-background concentration ratio of 4 : 1 were acquired on a GE Discovery 710 and a Siemens Biograph mCT and reconstructed with RM and TOF...
April 25, 2017: Nuclear Medicine Communications
Brian A Hargreaves, Valentina Taviani, Daniel V Litwiller, Daehyun Yoon
PURPOSE: To develop a fast 2D method for MRI near metal with reduced B0 in-plane and through-slice artifacts. METHODS: Multi-spectral imaging (MSI) approaches reduce artifacts in MR images near metal, but require 3D imaging of multiple excited volumes regardless of imaging geometry or artifact severity. The proposed 2D MSI method rapidly excites a limited slice and spectral region using gradient reversal between excitation and refocusing pulses, then uses standard 2D imaging, with the process repeating to cover multiple spectral offsets that are combined as in other MSI techniques...
April 25, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Eric Aliotta, Kévin Moulin, Daniel B Ennis
PURPOSE: To design and evaluate eddy current-nulled convex optimized diffusion encoding (EN-CODE) gradient waveforms for efficient diffusion tensor imaging (DTI) that is free of eddy current-induced image distortions. METHODS: The EN-CODE framework was used to generate diffusion-encoding waveforms that are eddy current-compensated. The EN-CODE DTI waveform was compared with the existing eddy current-nulled twice refocused spin echo (TRSE) sequence as well as monopolar (MONO) and non-eddy current-compensated CODE in terms of echo time (TE) and image distortions...
April 25, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Tonghe Wang, Lei Zhu
PURPOSE: As iterative CT reconstruction continues to advance, the spatial distribution of noise standard deviation (STD) and accurate noise power spectrum (NPS) on the reconstructed CT images become important for method evaluation as well as optimization of algorithm parameters. Using a single CT scan, we propose a practical method for pixel-wise calculation of noise statistics on an iteratively reconstructed CT image, which enables accurate calculation of noise STD for each pixel and NPS...
April 26, 2017: Medical Physics
Rolf Symons, Bernhard Krauss, Pooyan Sahbaee, Tyler E Cork, Manu N Lakshmanan, David A Bluemke, Amir Pourmorteza
PURPOSE: To demonstrate the feasibility of spectral imaging using photon-counting detector (PCD) x-ray computed tomography (CT) for simultaneous material decomposition of 3 contrast agents in vivo in a large animal model. METHODS: This Institutional Animal Care and Use Committee-approved study used a canine model. Bismuth subsalicylate was administered orally 24-72 hours before imaging. PCD CT was performed during intravenous administration of 40-60 ml gadoterate meglumine; 3...
April 26, 2017: Medical Physics
Yi-Huei Huang, Chieh-Shen Hu, Yi-Jhen Ke, Chiao-Hsi Chiang, Po-Da Hong, Ming-Kung Yeh
Needle-free jet injections constitute a crucial method for drug delivery. A novel liquid drug delivery system has been proposed recently, in which pressure atomizes liquid before delivering that atomized liquid to the patient's body; however, the mechanism and efficiency of the system are unclear. This study explored the shot delivery pressure, penetration depth, and cumulative amount of permeation of this system. This system was used to deliver 0.5% (w/v) methylene blue to agarose phantoms at various shot delivery pressures...
April 25, 2017: Drug Delivery and Translational Research
Sangmin Lee, Chaeyeong Lee, Eun Hyuk Shin, Sungkoo Cho, Dae-Hyun Kim, Youngyih Han, Doo Ho Choi, Sung-Joon Ye, Jin Sung Kim
The primary objective of this study was to measure secondary neutron dose during proton therapy using a detector that covers the entire neutron energy range produced in proton therapy. We analyzed and compared the neutron dose during proton treatment with passive scattering and line scanning. The neutron ambient dose equivalents were measured with a 190 MeV wobbling and line-scanning proton beam. The center of a plastic water phantom (30 × 30 × 60 cm3) was placed at the isocenter. A Wide-Energy Neutron Detection Instrument (WENDI-2) was located 1m from the isocenter at four different angles (0°, 45°, 90° and 135°)...
April 24, 2017: Radiation Protection Dosimetry
Hyo-Min Cho, Huanjun Ding, Nikita Kumar, David Sennung, Sabee Molloi
The aim of this study is to investigate the feasibility of water and lipid as calibration phantoms for accurate dual energy breast density quantification. Dual energy calibration was performed on a mammography system based on scanning multi-slit Si strip photon-counting detectors using plastic water and adipose-equivalent phantoms as the basis materials. Two different methods were used to convert the dual energy decomposition measurements in plastic phantom thicknesses into the true water and lipid basis materials...
April 25, 2017: Physics in Medicine and Biology
David A P Dunkerley, Jordan M Slagowski, Tobias Funk, Michael A Speidel
Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system capable of tomosynthesis-based 3-D catheter tracking. This work proposes a method of dose-reduced 3-D catheter tracking using dynamic electronic collimation (DEC) of the SBDX scanning x-ray tube. This is achieved through the selective deactivation of focal spot positions not needed for the catheter tracking task. The technique was retrospectively evaluated with SBDX detector data recorded during a phantom study. DEC imaging of a catheter tip at isocenter required 340 active focal spots per frame versus 4473 spots in full field-of-view (FOV) mode...
April 2017: Journal of Medical Imaging
Kurt Schilling, Vishwesh Nath, Justin A Blaber, Prasanna Parvathaneni, Adam W Anderson, Bennett A Landman
Q-ball imaging (QBI) is a popular high angular resolution diffusion imaging (HARDI) technique used to study brain architecture in vivo. Simulation and phantom-based studies suggest that QBI results are affected by the b-value, the number of diffusion weighting directions, and the signal-to-noise ratio (SNR). However, optimal acquisition schemes for QBI in clinical settings are largely undetermined given empirical (observed) imaging considerations. In this study, we acquire a HARDI dataset at five b-values with 11 repetitions on a single subject to investigate the effects of acquisition scheme and subsequent analysis models on the accuracy and precision of measures of tissue composition and fiber orientation derived from clinically feasible QBI at 3T...
April 21, 2017: Magnetic Resonance Imaging
Konstantinos Papoutsis, Linqing Li, Jamie Near, Stephen Payne, Peter Jezzard
Atherosclerotic plaques in the bifurcation of the carotid arteries can pose a significant health risk due to possible plaque rupture and subsequent stroke. The assessment of plaques, and evaluation of the risk they pose, can be performed with Black-Blood (BB) vessel wall magnetic resonance imaging. However, resolution at standard clinical field strengths (up to 3T) is limited, hampering reliable assessment and diagnosis. The aim of this study was to investigate the benefits of 7T MRI using a BB application that has been successful at clinical field strengths...
April 21, 2017: Magnetic Resonance Imaging
Kimberly L Chan, Muhammad G Saleh, Georg Oeltzschner, Peter B Barker, Richard A E Edden
It has previously been shown that the HERMES method ('Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy') can be used to simultaneously edit pairs of metabolites (such as N-acetyl-aspartate (NAA) and N-acetyl aspartyl glutamate (NAAG), or glutathione and GABA). In this study, HERMES is extended for the simultaneous editing of three overlapping signals, and illustrated for the example of NAA, NAAG and Aspartate (Asp). Density-matrix simulations were performed in order to optimize the HERMES sequence...
April 21, 2017: NeuroImage
Chuxiong Ding, Stephen G Chun, Baran D Sumer, Lucien A Nedzi, Ramzi E Abdulrahman, John S Yordy, Pam Lee, Brian Hrycushko, Timothy D Solberg, Chul Ahn, Robert D Timmerman, David L Schwartz
The purpose of this study was to commission and clinically test a robotic stereotactic delivery system (CyberKnife, Sunnyvale, CA) to treat early-stage glottic laryngeal cancer. We enrolled 15 patients with cTis-T2N0M0 carcinoma of the glottic larynx onto an institutional review board (IRB)-approved clinical trial. Stereotactic body radiotherapy (SBRT) plans prescribed 45 Gy/10 fractions to the involved hemilarynx. SBRT dosimetry was compared with (1) standard carotid-sparing laryngeal intensity-modulated radiation therapy (IMRT) and (2) selective hemilaryngeal IMRT...
April 21, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
C Ross Schmidtlein, Yizun Lin, Si Li, Andrzej Krol, Bradley J Beattie, John L Humm, Yuesheng Xu
PURPOSE: Performance of the preconditioned alternating projection algorithm (PAPA) using relaxed ordered subsets (ROS) with a non-smooth penalty function was investigated in positron emission tomography (PET). A higher order total variation (HOTV) regularizer was applied and a method for unsupervised selection of penalty weights based on the measured data is introduced. METHODS: A ROS version of PAPA with HOTV penalty (ROS-HOTV-PAPA) for PET image reconstruction was developed and implemented...
April 24, 2017: Medical Physics
Francesco Pisana, Thomas Henzler, Stefan Schönberg, Ernst Klotz, Bernhard Schmidt, Marc Kachelrieß
PURPOSE: Dynamic CT perfusion (CTP) consists in repeated acquisitions of the same volume in different time steps, slightly before, during and slightly afterwards the injection of contrast media. Important functional information can be derived for each voxel, which reflect the local hemodynamic properties and hence the metabolism of the tissue. Different approaches are being investigated to exploit data redundancy and prior knowledge for noise reduction of such datasets, ranging from iterative reconstruction schemes to high dimensional filters...
April 24, 2017: Medical Physics
Pascal Hauri, Roger A Hälg, Uwe Schneider
PURPOSE: The use of X-ray imaging in radiation therapy can give a substantial dose to the patient. A Cobalt machine combined with an magnetic resonance imaging (MRI) was recently introduced to clinical work. One positive aspect of using non-ionizing imaging devices is the reduction of the patient exposure. The purpose of this study was to quantify the difference in out-of-field dose to the patient between the image guided radiation therapy (IGRT) treatment applied with a linear accelerator with cone beam CT (CBCT) equipment and a Cobalt machine combined with an MRI...
April 24, 2017: Medical Physics
Taly Schmidt, Rina Barber, Emil Sidky
The proposed spectral CT method solves the constrained one-step spectral CT reconstruction (cOSSCIR) optimization problem to estimate basis material maps while modeling the nonlinear X-ray detection process and enforcing convex constraints on the basis map images. In order to apply the optimization-based reconstruction approach to experimental data, the presented method empirically estimates the effective energy-window spectra using a calibration procedure. The amplitudes of the estimated spectra were further optimized as part of the reconstruction process to reduce ring artifacts...
April 24, 2017: IEEE Transactions on Medical Imaging
Sara Park, Jongseong Jang, Jeesu Kim, Young Soo Kim, Chulhong Kim
Imaging that fuses multiple modes has become a useful tool for diagnosis and therapeutic monitoring. As a next step, real-time fusion imaging has attracted interest as for a tool to guide surgery. One widespread fusion imaging technique in surgery combines real-time ultrasound (US) imaging and preacquired magnetic resonance (MR) imaging. However, US imaging visualizes only structural information with relatively low contrast. Here, we present a photoacoustic (PA), US, and MR fusion imaging system which integrates a clinical PA and US imaging system with an optical tracking-based navigation subsystem...
April 24, 2017: IEEE Transactions on Medical Imaging
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