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https://www.readbyqxmd.com/read/28432828/quantitative-contrast-enhanced-spectral-mammography-based-on-photon-counting-detectors-a-feasibility-study
#1
Huanjun Ding, Sabee Molloi
PURPOSE: To investigate the feasibility of accurate quantification of iodine mass thickness in contrast-enhanced spectral mammography. MATERIALS AND METHODS: A computer simulation model was developed to evaluate the performance of a photon-counting spectral mammography system in the application of contrast-enhanced spectral mammography. A figure-of-merit (FOM), which was defined as the decomposed iodine signal-to-noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and pre-filtrations for breasts of various thicknesses and densities...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432674/partial-volume-correction-of-brain-pet-studies-using-iterative-deconvolution-in-combination-with-hypr-denoising
#2
Sandeep S V Golla, Mark Lubberink, Bart N M van Berckel, Adriaan A Lammertsma, Ronald Boellaard
BACKGROUND: Accurate quantification of PET studies depends on the spatial resolution of the PET data. The commonly limited PET resolution results in partial volume effects (PVE). Iterative deconvolution methods (IDM) have been proposed as a means to correct for PVE. IDM improves spatial resolution of PET studies without the need for structural information (e.g. MR scans). On the other hand, deconvolution also increases noise, which results in lower signal-to-noise ratios (SNR). The aim of this study was to implement IDM in combination with HighlY constrained back-PRojection (HYPR) denoising to mitigate poor SNR properties of conventional IDM...
December 2017: EJNMMI Research
https://www.readbyqxmd.com/read/28432504/3t-mri-of-the-knee-with-optimised-isotropic-3d-sequences-accurate-delineation-of-intra-articular-pathology-without-prolonged-acquisition-times
#3
Osamah M Abdulaal, Louise Rainford, Peter MacMahon, Eoin Kavanagh, Marie Galligan, James Cashman, Allison McGee
OBJECTIVES: To investigate optimised isotropic 3D turbo spin echo (TSE) and gradient echo (GRE)-based pulse sequences for visualisation of articular cartilage lesions within the knee joint. METHODS: Optimisation of experimental imaging sequences was completed using healthy volunteers (n=16) with a 3-Tesla (3T) MRI scanner. Imaging of patients with knee cartilage abnormalities (n=57) was then performed. Acquired sequences included 3D proton density-weighted (PDW) TSE (SPACE) with and without fat-suppression (FS), and T2*W GRE (TrueFISP) sequences, with acquisition times of 6:51, 6:32 and 5:35 min, respectively...
April 21, 2017: European Radiology
https://www.readbyqxmd.com/read/28431338/the-design-and-fabrication-of-beta-sensor-system-for-in-situ-diffusion-tests-in-mudstone-in-france
#4
Zhenhua Lin, Olivier Tillement, Marie-Genevieve Blanchin, Vivek Jindal, Agnès Vinsot, Romain V H Dagnelie, Virginie Blin, Yanick Lettry, Benoit Hautefeuille
Long term in situ diffusion experiments in the Callovian-Oxfordian mudstone (France) are designed in the context of nuclear waste management. β-emitters HTO and (36)Cl radiotracers are representative of neutral and anionic species in these experiments. Studies have been carried out to design an in situ beta monitoring system in order to quantify tracer migration in the rock pore water over time. The development, design and calibration of β-emitter radiation sensors were performed. An optimised geometry was calculated for the detection chamber of (36)Cl in solution (Ø×L=30×2mm(2)) via Monte-Carlo N-Particle transport simulation tools...
April 1, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28431306/difference-optimization-automatic-correction-of-relative-frequency-and-phase-for-mean-non-edited-and-edited-gaba-1-h-mega-press-spectra
#5
Marianne Cleve, Martin Krämer, Alexander Gussew, Jürgen R Reichenbach
Phase and frequency corrections of magnetic resonance spectroscopic data are of major importance to obtain reliable and unambiguous metabolite estimates as validated in recent research for single-shot scans with the same spectral fingerprint. However, when using the J-difference editing technique (1)H MEGA-PRESS, misalignment between mean edited (ON‾) and non-edited (OFF‾) spectra that may remain even after correction of the corresponding individual single-shot scans results in subtraction artefacts compromising reliable GABA quantitation...
April 7, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28430716/simultaneous-multislice-accelerated-turbo-spin-echo-magnetic-resonance-imaging-comparison-and-combination-with-in-plane-parallel-imaging-acceleration-for-high-resolution-magnetic-resonance-imaging-of-the-knee
#6
Jan Fritz, Benjamin Fritz, Jialu Zhang, Gaurav K Thawait, Dharmdev H Joshi, Li Pan, Dingxin Wang
PURPOSE: We prospectively quantified the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of integrated parallel acquisition technique (PAT) and simultaneous multislice (SMS) acceleration and various combinations thereof, and we further compared two 4-fold-accelerated (PAT2-SMS2) high-resolution turbo spin echo (TSE) magnetic resonance imaging (MRI) protocols of the knee against a clinical 2-fold-accelerated (PAT2-SMS1) TSE standard. MATERIALS AND METHODS: Institutional review board approval was obtained, and all subjects gave informed consent...
April 20, 2017: Investigative Radiology
https://www.readbyqxmd.com/read/28430226/stable-nanosecond-passively-q-switched-all-fiber-erbium-doped-laser-with-a-45%C3%A2-tilted-fiber-grating
#7
Tianxing Wang, Zhijun Yan, Chengbo Mou, Kaiming Zhou, Lin Zhang
Nanosecond passive Q-switching generation from an all-fiber erbium-doped laser with a UV inscribed 45° tilted fiber grating (TFG) is systematically demonstrated. The 45° TFG is employed as a polarizer together with two polarization controllers (PCs) to realize nonlinear polarization rotation (NPR). Because of the NPR effect, stable Q-switched pulses with an average output power of 17.5 mW, a single pulse energy of 72.7 nJ, a repetition rate of 241 kHz, a pulse width of 466 ns, and a signal to noise ratio (SNR) of 58...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28429574/flip-angle-optimization-for-balanced-ssfp-cardiac-cine-imaging-following-the-application-of-standard-extracellular-contrast-agent-gadobutrol
#8
Daniel L R Kuetting, Darius Dabir, Julian Luetkens, Andreas Feisst, Rami Homsi, Daniel Thomas, Hans H Schild, Alois M Sprinkart
PURPOSE: To investigate the effect of the flip angle (FA) on the blood-myocardium contrast and to define the FA leading to highest image quality in contrast-enhanced balanced steady-state free precession (bSSFP) images. bSSFP images provide excellent contrast between myocardium and blood with high signal-to-noise and contrast-to-noise ratios (SNR, CNR). In clinical practice, bSSFP images are typically acquired following the injection of extracellular contrast agents (ECAs), although ECAs decrease the blood-myocardium contrast...
April 21, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28425452/estimating-the-irreversible-pressure-drop-across-a-stenosis-by-quantifying-turbulence-production-using-4d-flow-mri
#9
Hojin Ha, Jonas Lantz, Magnus Ziegler, Belen Casas, Matts Karlsson, Petter Dyverfeldt, Tino Ebbers
The pressure drop across a stenotic vessel is an important parameter in medicine, providing a commonly used and intuitive metric for evaluating the severity of the stenosis. However, non-invasive estimation of the pressure drop under pathological conditions has remained difficult. This study demonstrates a novel method to quantify the irreversible pressure drop across a stenosis using 4D Flow MRI by calculating the total turbulence production of the flow. Simulation MRI acquisitions showed that the energy lost to turbulence production can be accurately quantified with 4D Flow MRI within a range of practical spatial resolutions (1-3 mm; regression slope = 0...
April 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28424572/functional-sensitivity-of-2d-simultaneous-multi-slice-echo-planar-imaging-effects-of-acceleration-on-g-factor-and-physiological-noise
#10
Nick Todd, Oliver Josephs, Peter Zeidman, Guillaume Flandin, Steen Moeller, Nikolaus Weiskopf
Accelerated data acquisition with simultaneous multi-slice (SMS) imaging for functional MRI studies leads to interacting and opposing effects that influence the sensitivity to blood oxygen level-dependent (BOLD) signal changes. Image signal to noise ratio (SNR) is decreased with higher SMS acceleration factors and shorter repetition times (TR) due to g-factor noise penalties and saturation of longitudinal magnetization. However, the lower image SNR is counteracted by greater statistical power from more samples per unit time and a higher temporal Nyquist frequency that allows for better removal of spurious non-BOLD high frequency signal content...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/28422238/3d-single-molecule-tracking-enables-direct-hybridization-kinetics-measurement-in-solution
#11
Cong Liu, Judy M Obliosca, Yen-Liang Liu, Yu-An Chen, Ning Jiang, Hsin-Chih Yeh
Single-molecule measurements of DNA hybridization kinetics are mostly performed on a surface or inside a trap. Here we demonstrate a time-resolved, 3D single-molecule tracking (3D-SMT) method that allows us to follow a freely diffusing ssDNA molecule in solution for hundreds of milliseconds or even seconds and observe multiple annealing and melting events taking place on the same molecule. This is achieved by combining confocal-feedback 3D-SMT with time-domain fluorescence lifetime measurement, where fluorescence lifetime serves as the indicator of hybridization...
April 19, 2017: Nanoscale
https://www.readbyqxmd.com/read/28421243/assessment-of-70-kev-virtual-monoenergetic-spectral-images-in-abdominal-ct-imaging-a-comparison-study-to-conventional-polychromatic-120-kvp-images
#12
Negin Rassouli, Hamid Chalian, Prabhakar Rajiah, Amar Dhanantwari, Luis Landeras
PURPOSE: To evaluate the image quality of 70-keV virtual monoenergetic (monoE) abdominal CT images compared to 120-kVp polychromatic images generated from a spectral detector CT (SDCT) scanner. METHODS: This prospective study included generation of a 120-kVp polychromatic dataset and a 70-keV virtual monoE dataset after a single contrast-enhanced CT acquisition on a SDCT scanner (Philips Healthcare) during portal venous phase. The attenuation values (HU), noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured in the liver, spleen, pancreas, kidney, aorta, portal vein, and muscle...
April 18, 2017: Abdominal Radiology
https://www.readbyqxmd.com/read/28420215/a-phonocardiographic-based-fiber-optic-sensor-and-adaptive-filtering-system-for-noninvasive-continuous-fetal-heart-rate-monitoring
#13
Radek Martinek, Jan Nedoma, Marcel Fajkus, Radana Kahankova, Jaromir Konecny, Petr Janku, Stanislav Kepak, Petr Bilik, Homer Nazeran
This paper focuses on the design, realization, and verification of a novel phonocardiographic- based fiber-optic sensor and adaptive signal processing system for noninvasive continuous fetal heart rate (fHR) monitoring. Our proposed system utilizes two Mach-Zehnder interferometeric sensors. Based on the analysis of real measurement data, we developed a simplified dynamic model for the generation and distribution of heart sounds throughout the human body. Building on this signal model, we then designed, implemented, and verified our adaptive signal processing system by implementing two stochastic gradient-based algorithms: the Least Mean Square Algorithm (LMS), and the Normalized Least Mean Square (NLMS) Algorithm...
April 18, 2017: Sensors
https://www.readbyqxmd.com/read/28417101/role-of-active-listening-and-listening-effort-on-contralateral-suppression-of-transient-evoked-otoacousic-emissions
#14
Mohan Kumar Kalaiah, Nikhitha B Theruvan, Kaushlendra Kumar, Jayashree S Bhat
BACKGROUND AND OBJECTIVES: The present study aimed to investigate the effect of active listening and listening effort on the contralateral suppression of transient evoked otoacoustic emissions (CSTEOAEs). SUBJECTS AND METHODS: Twenty eight young adults participated in the study. Transient evoked otoacoustic emissions (TEOAEs) were recorded using 'linear' clicks at 60 dB peSPL, in three contralateral noise conditions. In condition 1, TEOAEs were obtained in the presence of white noise in the contralateral ear...
April 2017: Journal of Audiology & Otology
https://www.readbyqxmd.com/read/28412952/rayleigh-maximum-likelihood-bilateral-filter-for-ultrasound-image-enhancement
#15
Haiyan Li, Jun Wu, Aimin Miao, Pengfei Yu, Jianhua Chen, Yufeng Zhang
BACKGROUND: Ultrasound imaging plays an important role in computer diagnosis since it is non-invasive and cost-effective. However, ultrasound images are inevitably contaminated by noise and speckle during acquisition. Noise and speckle directly impact the physician to interpret the images and decrease the accuracy in clinical diagnosis. Denoising method is an important component to enhance the quality of ultrasound images; however, several limitations discourage the results because current denoising methods can remove noise while ignoring the statistical characteristics of speckle and thus undermining the effectiveness of despeckling, or vice versa...
April 17, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28411437/design-and-construction-of-a-novel-1-h-19-f-double-tuned-coil-system-using-pin-diode-switches-at-9-4t
#16
Chang-Hoon Choi, Suk-Min Hong, YongHyun Ha, N Jon Shah
A double-tuned (1)H/(19)F coil using PIN-diode switches was developed and its performance evaluated. The is a key difference from the previous developments being that this design used a PIN-diode switch in series with an additionally inserted inductor in parallel to one of the capacitors on the loop. The probe was adjusted to (19)F when the reverse bias voltage was applied (PIN-diode OFF), whilst it was switched to (1)H when forward current was flowing (PIN-diode ON). S-parameters and Q-factors of single- and double-tuned coils were examined and compared with/without a phantom on the bench...
April 7, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28410679/dual-energy-imaging-method-to-improve-the-image-quality-and-the-accuracy-of-dose-calculation-for-cone-beam-computed-tomography
#17
Kuo Men, Jianrong Dai, Xinyuan Chen, Minghui Li, Ke Zhang, Peng Huang
PURPOSE: To improve the image quality and accuracy of dose calculation for cone-beam computed tomography (CT) images through implementation of a dual-energy cone-beam computed tomography method (DE-CBCT), and evaluate the improvement quantitatively. METHODS: Two sets of CBCT projections were acquired using the X-ray volumetric imaging (XVI) system on a Synergy (Elekta, Stockholm, Sweden) system with 120kV (high) and 70kV (low) X-rays, respectively. Then, the electron density relative to water (relative electron density (RED)) of each voxel was calculated using a projection-based dual-energy decomposition method...
April 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28410615/signal-to-noise-ratio-evaluation-of-magnetic-resonance-images-in-the-presence-of-an-ultrasonic-motor
#18
Peyman Shokrollahi, James M Drake, Andrew A Goldenberg
BACKGROUND: Safe robot-assisted intervention using magnetic resonance imaging (MRI) guidance requires the precise control of assistive devices, and most currently available tools are rarely MRI-compatible. To obtain high precision, it is necessary to characterize and develop existing MRI-safe actuators for use in a high magnetic field (≥3 T). Although an ultrasonic motor (USM) is considered to be an MRI-safe actuator, and can be used in the vicinity of a high field scanner, its presence interferes with MR images...
April 14, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28410386/radiation-dose-reduction-in-pediatric-great-vessel-stent-computed-tomography-using-iterative-reconstruction-a-phantom-study
#19
Annemarie M den Harder, Dominika Suchá, Pieter J van Doormaal, Ricardo P J Budde, Pim A de Jong, Arnold M R Schilham, Johannes M P J Breur, Tim Leiner
BACKGROUND: To study dose reduction using iterative reconstruction (IR) for pediatric great vessel stent computed tomography (CT). METHODS: Five different great vessel stents were separately placed in a gel-containing plastic holder within an anthropomorphic chest phantom. The stent lumen was filled with diluted contrast gel. CT acquisitions were performed at routine dose, 52% and 81% reduced dose and reconstructed with filtered back projection (FBP) and IR. Objective image quality in terms of noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) as well as subjective image quality were evaluated...
2017: PloS One
https://www.readbyqxmd.com/read/28409258/impact-of-knowledge-based-iterative-model-reconstruction-on-myocardial-late-iodine-enhancement-in-computed-tomography-and-comparison-with-cardiac-magnetic-resonance
#20
Yuki Tanabe, Teruhito Kido, Akira Kurata, Naoki Fukuyama, Takahiro Yokoi, Tomoyuki Kido, Teruyoshi Uetani, Mani Vembar, Amar Dhanantwari, Shinichi Tokuyasu, Natsumi Yamashita, Teruhito Mochizuki
We evaluated the image quality and diagnostic performance of late iodine enhancement computed tomography (LIE-CT) with knowledge-based iterative model reconstruction (IMR) for the detection of myocardial infarction (MI) in comparison with late gadolinium enhancement magnetic resonance imaging (LGE-MRI). The study investigated 35 patients who underwent a comprehensive cardiac CT protocol and LGE-MRI for the assessment of coronary artery disease. The CT protocol consisted of stress dynamic myocardial CT perfusion, coronary CT angiography (CTA) and LIE-CT using 256-slice CT...
April 13, 2017: International Journal of Cardiovascular Imaging
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