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Magnetic Resonance Imaging

Gavin D Merrifield, James Mullin, Lindsay Gallagher, Carl Tucker, Maurits A Jansen, Martin Denvir, William M Holmes
Increasing scientific interest in the zebrafish as a model organism across a range of biomedical and biological research areas raises the need for the development of in vivo imaging tools appropriate to this subject. Development of the embryonic and early stage forms of the subject can currently be assessed using optical based techniques due to the transparent nature of the species at these early stages. However this is not an option during the juvenile and adult stages when the subjects become opaque. Magnetic Resonance Imaging (MRI) techniques would allow for the longitudinal and non-invasive assessment of development and health in these later life stages...
October 14, 2016: Magnetic Resonance Imaging
Zewei Wang, Qing Yang, Li Min Chen
The goals of this study are to characterize the temporal dynamics of inter-regional connectivity of the brain in chronic headache (CH) patients versus their age/gender matched controls (CONCH, n=28 pairs), and to determine whether dynamic measures reveal additional features to static functional connectivity and correlate with psychometric scores. Cortical thickness and inter-regional resting state fMRI connectivity were quantified and compared between CH and CONCH groups. Six cortical regions of interest (ROI) pairs that exhibited correlated cortical thickness and static functional connectivity abnormalities were selected for temporal dynamic analysis...
October 14, 2016: Magnetic Resonance Imaging
Abdul Haseeb Ahmed, Ijaz M Qureshi, Jawad Ali Shah, Muhammad Zaheer
Respiratory motion during Magnetic Resonance (MR) acquisition causes strong blurring artifacts in the reconstructed images. These artifacts become more pronounced when use with the fast imaging reconstruction techniques like compressed sensing (CS). Recently, an MR reconstruction technique has been done with the help of compressed sensing (CS), to provide good quality sparse images from the highly under-sampled k-space data. In order to maximize the benefits of CS, it is obvious to use CS with the motion corrected samples...
October 13, 2016: Magnetic Resonance Imaging
I G Murphy, M J Graves, S Reid, A J Patterson, I Patterson, A N Priest, D J Lomas
PURPOSE: Hepatic magnetic resonance elastography (MRE) is currently a breath-hold imaging technique. Patients with chronic liver disease can have comorbidities that limit their ability to breath-hold (BH) for the required acquisition time. Our aim was to evaluate whether stiffness measurements obtained from a navigator-triggered MRE acquisition are comparable to standard expiratory breath-hold, inspiratory breath-hold or free-breathing in healthy participants. MATERIALS AND METHODS: Twelve healthy participants were imaged using the four methods on a clinical 1...
October 13, 2016: Magnetic Resonance Imaging
Ashish Phophalia, Suman K Mitra
In this paper, we have presented a two stage method, using Kernel Principal Componenet Analysis (KPCA) and Rough Set Theory (RST), for denoising volumetric MRI data. A Rough Set Theory (RST) based clustering technique has been used for voxel based processing. The method groups similar voxels (3D cubes) using class and edge information derived from noisy input. Each cluster thus formed now represented via basis vector. These vectors now projected into to kernel space and PCA is performed in the feature space...
October 13, 2016: Magnetic Resonance Imaging
Farid Ahmed Sid, Karim Abed-Meraim, Rachid Harba, Fatima Oulebsir-Boumghar
PURPOSE: To examine the effects of MR acquisition parameters on brain white matter fiber orientation estimation and parameter of clinical interest in crossing fiber areas based on the Multi-Tensor Model (MTM). MATERIAL AND METHODS: We compute the Cramér-Rao Bound (CRB) for the MTM and the parameter of clinical interest such as the Fractional Anisotropy (FA) and the dominant fiber orientations, assuming that the diffusion MRI data are recorded by a multi-coil, multi-shell acquisition system...
October 12, 2016: Magnetic Resonance Imaging
Somaie Salajeghe, Paul Babyn, Gordon E Sarty
BACKGROUND: In B1 encoded MRI, a realistic non-linear phase RF encoding coil will generate an inhomogeneous B1 field that leads to spatially dependent flip angles. The non-linearity of the B1 phase gradient can be compensated for in the reconstruction, but B1 inhomogeneity remains a problem. The effect of B1 inhomogeneity on tip angles for conventional, B0 encoded MRI, may be minimized using composite pulses. The objective of this study was to explore the feasibility of using composite pulses with non-linear RF phase encoding coils and to identify the most appropriate composite pulse scheme...
October 12, 2016: Magnetic Resonance Imaging
Dejing Ma, Feng Lu, Xuexue Zou, Hu Zhang, Yangyang Li, Lin Zhang, Liang Chen, Dongjing Qin, Bin Wang
PURPOSE: To investigate the value of use of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) as an adjunct to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to distinguish benign from malignant breast lesions. MATERIALS AND METHODS: Retrospective analysis of data pertaining to 117 patients with breast lesions who underwent DCE-MRI and IVIM-DWI examination with 3.0T MRI was conducted. A total of 128 lesions were pathologically confirmed (47 benign and 81 malignant)...
October 11, 2016: Magnetic Resonance Imaging
Nelson F Velasco, Andrea Rueda, Cristina Santa Marta, Eduardo Romero
High-quality Cardiac Magnetic Resonance (CMR) images can be hardly obtained when intrinsic noise sources are present, namely heart and breathing movements. Yet heart images may be acquired in real time, the image quality is really limited and most sequences use ECG gating to capture images at each stage of the cardiac cycle during several heart beats. This paper presents a novel super-resolution algorithm that improves the cardiac image quality using a sparse Bayesian approach. The high-resolution version of the cardiac image is constructed by combining the information of the low-resolution series -observations from different non-orthogonal series composed of anisotropic voxels- with a prior distribution of the high-resolution local coefficients that enforces sparsity...
October 11, 2016: Magnetic Resonance Imaging
Karol Borkowski, Krzysztof Kłodowski, Henryk Figiel, Artur Tadeusz Krzyżak
The recently presented B-matrix Spatial Distribution (BSD) approach is a calibration technique which derives the actual distribution of the B-matrix in space. It is claimed that taking into account the spatial variability of the B-matrix improves the accuracy of diffusion tensor imaging (DTI). The purpose of this study is to verify this approach theoretically through computer simulations. Assuming three different spatial distributions of the B-matrix, diffusion weighted signals were calculated for the six orientations of a model anisotropic phantom...
October 11, 2016: Magnetic Resonance Imaging
Robert J Young, Ek T Tan, Kyung K Peck, Mehrnaz Jenabi, Sasan Karimi, Nicole Brennan, Jennifer Rubel, John Lyo, Weiji Shi, Zhigang Zhang, Marcel Prastawa, Xiaofeng Liu, Jonathan I Sperl, Robin Fatovic, Luca Marinelli, Andrei I Holodny
PURPOSE: To compare compressed diffusion spectrum imaging (CS-DSI) with diffusion tensor imaging (DTI) in patients with intracranial masses. We hypothesized that CS-DSI would provide superior visualization of the motor and language tracts. MATERIALS AND METHODS: We retrospectively analyzed 25 consecutive patients with intracranial masses who underwent DTI and CS-DSI for preoperative planning. Directionally-encoded anisotropy maps, and streamline hand corticospinal motor tracts and arcuate fasciculus language tracts were graded according to a 3-point scale...
October 11, 2016: Magnetic Resonance Imaging
Peter Latta, Zenon Starčuk, Marco L H Gruwel, Michael H Weber, Boguslaw Tomanek
MR images are affected by system delays and gradient field imperfections which induce discrepancies between prescribed and actual k-space trajectories. This could be even more critical for non-Cartesian data acquisitions where even a small deviation from the assumed k-space trajectory results in severe image degradation and artifacts. Knowledge of the actual k-space trajectories is therefore crucial and can be incorporated in the reconstruction of high quality non-Cartesian images. A novel MR method for the calibration of actual gradient waveforms was developed using a combination of phase encoding increments and subsequent detection of the exact time point at which the corresponding trajectory is crossing the k-space origin...
October 11, 2016: Magnetic Resonance Imaging
Simona Marzi, Francesca Piludu, Chiara Forina, Giuseppe Sanguineti, Renato Covello, Giuseppe Spriano, Antonello Vidiri
OBJECTIVE: To correlate intravoxel incoherent motion (IVIM) imaging and dynamic contrast-enhanced (DCE) MRI in head and neck squamous cell carcinoma (HNSCC). METHODS: Forty untreated patients with HNSCC were included retrospectively in the study. Perfusion fraction f, diffusion coefficient D and perfusion-related diffusion coefficient D* were extracted by bi-exponential fitting of IVIM data. Semi-quantitative DCE-MRI parameters, including positive enhancement integral (PEI) and maximum slope of increase (MSI), were calculated...
October 11, 2016: Magnetic Resonance Imaging
Kousaku Saotome, Akira Matsushita, Koji Matsumoto, Yoshiaki Kato, Kei Nakai, Koichi Murata, Tetsuya Yamamoto, Yoshiyuki Sankai, Akira Matsumura
PURPOSE: A fast spin-echo sequence based on the Periodically Rotated Overlapping Parallel Lines with Enhanced Reconstruction (PROPELLER) technique is a magnetic resonance (MR) imaging data acquisition and reconstruction method for correcting motion during scans. Previous studies attempted to verify the in vivo capabilities of motion-corrected PROPELLER in real clinical situations. However, such experiments are limited by repeated, stray head motion by research participants during the prescribed and precise head motion protocol of a PROPELLER acquisition...
October 11, 2016: Magnetic Resonance Imaging
Chun Yang, Ceng Li, Mengsu Zeng, Xin Lu, Jingjing Li, Jiali Wang, Muhammad Umair Sami, Kai Xu
Non-CE MRA techniques (true steady-state free-precession, SSFP) have been used effectively for the selective visualization of the portal venous system and inferior vena cava. Budd-Chiari Syndrome (BCS) encompasses a number of conditions that cause the obstruction of the hepatic outflow tract from the small hepatic veins to the junction of the inferior vena cava (IVC) and right atrium. The purpose of this study was to diagnose BCS with IVC obstruction using respiratory triggered three-dimensional (3D) true SSFP with T-SLIP and compare to digital subtraction angiography (DSA)...
October 11, 2016: Magnetic Resonance Imaging
Nozomu Murata, Kiyoko Murata, Luis F Gonzalez-Cuyar, Kenneth Maravilla
Until recognition of the association of nephrogenic systemic fibrosis (NSF) and gadolinium based contrast agents (GBCA) in 2006, these agents were considered extremely safe and without major adverse effects. Even after the recognition of NSF, most physicians considered all GBCAs to be safe when used in patients with normal renal function. This belief has been called into question with the discovery by Kanda in 2014 that Gd is deposited in brain tissue in patients with normal kidney function. Since that initial report, there have been a number of important studies analyzing the effects of various GBCAs in brain using MR T1 signal intensity measurements and postmortem tissue analyses with inductively coupled plasma mass spectrometry...
October 5, 2016: Magnetic Resonance Imaging
Michael F Tweedle
The methodology and published work aimed at speciation of gadolinium based contrast agents in tissues is reviewed. The discussion focusses on the context of Gd deposited long term in tissue following administration of the contrast agents. Detection of Gd without identification of the chemical form detected is simple and straight forward using a variety of methods. Determination of the chemical form of Gd detected is far more complex and most method require inherently imperfect extraction steps that can alter the Gd chemical species detected...
September 30, 2016: Magnetic Resonance Imaging
Joana Ramalho, Miguel Ramalho, Michael Jay, Lauren Burke, Richard C Semelka
GBCAs play an important role in the diagnostic evaluation of many patients. The safety of these agents has been once again questioned after gadolinium deposits were observed and measured in brain and bone of patients with normal renal function. This retention of gadolinium in the human body has been termed "gadolinium storage condition". The long- term and cumulative effects of retained gadolinium in the brain and elsewhere are not as yet understood. Recently, patients who report that they suffer from chronic symptoms secondary to gadolinium exposure and retention created gadolinium-toxicity on-line support groups...
September 27, 2016: Magnetic Resonance Imaging
Joana Ramalho, Miguel Ramalho, Mamdoh AlObaidy, Richard C Semelka
Over the last 2years several studies have been published regarding gadolinium deposition in brain structures in patients with normal renal function after repeated administrations of gadolinium-based contrast agents (GBCAs). Most of the publications are magnetic resonance imaging (MRI) based retrospective studies, where gadolinium deposition may be indirectly measured by evaluating changes in T1 signal intensity (SI) in brain tissue, particularly in the dentate nucleus (DN) and/or globus pallidi (GP). The direct correlation between T1 signal changes and gadolinium deposition was validated by human pathology studies...
September 27, 2016: Magnetic Resonance Imaging
Richard C Semelka, Miguel Ramalho, Michael Jay
This summary attempts to provide forward-looking concepts regarding gadolinium related toxicity, as discussed in further detail in this issue.
September 14, 2016: Magnetic Resonance Imaging
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