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Magnetic Resonance Imaging

Robert V Bergen, Lawrence Ryner
Image artifacts due to 14 gauge radiotherapy electromagnetic (EM) transponders were assessed on conventional spin echo images, and corrected using metal artifact reduction techniques: high bandwidth, view angle tilting (VAT), and slice encoding for metal artifact correction (SEMAC). Large areas of signal loss and/or pile-up were produced in an area extending up to 15.3 mm in radius for 14G transponders in standard imaging. Using high bandwidth imaging with VAT, in-plane artifact sizes were reduced by up to 35%...
February 17, 2019: Magnetic Resonance Imaging
Maribel Torres-Velázquez, Emily A Sawin, Jacqueline M Anderson, John-Paul J Yu
Alterations in gut microbiome populations via dietary manipulation have been shown to induce diet-dependent changes in white matter microstructure. The purpose of this study is to examine the durability of these diet-induced microstructural alterations. We implemented a crossover experimental design where post-weaned male rats were assigned to one of four experimental diets. Following the administration of experimental diets and again following crossover and resumption of a normal diet, brains were imaged ex-vivo with diffusion tensor imaging...
February 15, 2019: Magnetic Resonance Imaging
Syed O Ali, Petros Fessas, Joshua D Kaggie, Fulvio Zaccagna, Gavin Houston, Scott Reid, Martin J Graves, Ferdia A Gallagher
The tumor microenvironment is characteristically acidic and this extracellular acidosis is known to play a role in carcinogenesis and metastasis and can affect tumor chemosensitivity and radiosensitivity. Intracellular pH has been used as a possible biomarker of salvageable tissue in ischemic stroke. A non-invasive MRI-based approach for the determination and imaging of cerebral pH would be a powerful tool in cancer diagnosis and monitoring, as well as stroke treatment planning. Several pH-based MRI imaging approaches have been proposed but for these to be useful, disentangling the effects of pH from other parameters which may affect the measured MRI signal is crucial to ensure accuracy and specificity...
February 13, 2019: Magnetic Resonance Imaging
Francesco Giganti, Armando Stabile, Simone Giona, José Marenco, Clement Orczyk, Caroline M Moore, Clare Allen, Alex Kirkham, Mark Emberton, Shonit Punwani
BACKGROUND: To assess multiparametric magnetic resonance imaging (mpMRI) characteristics in prostate cancer (PCa) before and after irreversible electroporation (IRE) and to investigate their correlation with the presence of post-operative recurrence of PCa. METHODS: MpMRI was performed in 30 men with PCa prior to treatment, after 10 days and at 6 months. An additional scan at 1 year was available for 18 men. Two radiologists assessed retrospectively the following parameters by planimetry: tumour volume, necrotic volume (early post-treatment scan) and residual fibrosis...
February 12, 2019: Magnetic Resonance Imaging
Margit Bristela, Astrid Skolka, Jaryna Eder, Pavol Szomolanyi, Michael Weber, Eva Piehslinger, Martina Schmid-Schwap, Siegfried Trattnig
INTRODUCTION: T2 mapping, as a quantitative biochemical MRI-technique that provides information on water and collagen fiber content and composition, was shown to be clinically feasible for the evaluation of healthy temporomandibular joints. OBJECTIVES: The aim of our study was to compare the T2 values of whole discs in patients with and without disc dislocation, to evaluate the possible influence of morphological findings on T2 values and to assess the interrater agreement...
February 9, 2019: Magnetic Resonance Imaging
Jonathan Andersson, Josefine Roswall, Emma Kjellberg, Håkan Ahlström, Jovanna Dahlgren, Joel Kullberg
CONTEXT: Brown adipose tissue is of metabolic interest. The tissue is however poorly explored in children. METHODS: Sixty-three 7-year old subjects from the Swedish birth-cohort Halland Health and Growth Study were recruited. Care was taken to include both normal weight and overweight children, but the subjects were otherwise healthy. Only children born full term were included. Water-fat separated whole-body MRI scans, anthropometric measurements, and measurements of fasting glucose and levels of energy homeostasis related hormones, including the insulin-sensitizer osteocalcin, were performed...
February 8, 2019: Magnetic Resonance Imaging
Kangjoo Lee, Hui Ming Khoo, Constance Fourcade, Jean Gotman, Christophe Grova
Resting state functional magnetic resonance imaging is used to study how brain regions are functionally connected by measuring temporal correlation of the fMRI signals, when a subject is at rest. Sparse dictionary learning is used to estimate a dictionary of resting state networks by decomposing the whole brain signals into several temporal features (atoms), each being shared by a set of voxels associated to a network. Recently, we proposed and validated a new method entitled Sparsity-based Analysis of Reliable K-hubness (SPARK), suggesting that connector hubs of brain networks participating in inter-network communication can be identified by counting the number of atoms involved in each voxel (sparse number k)...
January 26, 2019: Magnetic Resonance Imaging
Arthur Coste, Fawzi Boumezbeur, Alexandre Vignaud, Guillaume Madelin, Kathrin Reetz, Denis Le Bihan, Cécile Rabrait-Lerman, Sandro Romanzetti
PURPOSE: The state-of-the-art method to quantify sodium concentrations in vivo consists in a fully relaxed 3D spin-density (SD) weighted acquisition. Nevertheless, most sodium MRI clinical studies use short-TR SD acquisitions to reduce acquisition durations. We present a clinically viable implementation of the Variable Flip Angle (VFA) method for robust and clinically viable quantification of total sodium concentration (TSC) and longitudinal relaxation rates in vivo in human brain at 3 T...
January 26, 2019: Magnetic Resonance Imaging
Jizhong Duan, Zhongwen Bao, Yu Liu
Parallel Magnetic Resonance (MR) imaging is a well-established acceleration technique based on the spatial sensitivities of array receivers. Eigenvector-based SPIRiT (ESPIRiT) is a new parallel MR imaging reconstruction method that combines the advantages of the SENSE and GRAPPA methods. It estimates multiple sets of the sensitivity maps from the calibration matrix that is constructed from the auto-calibration data. To improve the quality of the reconstructed image, we introduced the Total Variation (TV) and ℓp pseudo-norm Joint TV (ℓp JTV) regularization terms to the ESPIRiT model for parallel MR imaging reconstruction, which were solved by using the Operator Splitting (OS) method...
January 25, 2019: Magnetic Resonance Imaging
Ye Li, Jo Lee, Lei Zhang, Qiaoyan Chen, Changjun Tie, Chao Luo, Xiaoliang Zhang, Dong Liang, Xin Liu, Hairong Zheng
PURPOSE: To offer the new head coil option (with a lower channel count) of an RF coil array that provides comparable performance to the commercial 32-channel head coil. METHODS: The coil system comprised an upper shield (ten channels) and bottom section (fourteen channels). Signal-to-noise ratio (SNR) values for 2D unaccelerated imaging and the g-factor with an acceleration factor of 2-4 were evaluated in a phantom study. SNR performance and human brain and intracranial vessel wall imaging were conducted as part of the in vivo study...
January 23, 2019: Magnetic Resonance Imaging
Kurt G Schilling, Fang-Cheng Yeh, Vishwesh Nath, Colin Hansen, Owen Williams, Susan Resnick, Adam W Anderson, Bennett A Landman
PURPOSE: The diffusion MRI "b-vector" table describing the diffusion sensitization direction can be flipped and permuted in dimension due to different orientation conventions used in scanners and incorrect or improperly utilized file formats. This can lead to incorrect fiber orientation estimates and subsequent tractography failure. Here, we present an automated quality control procedure to detect when the b-table is flipped and/or permuted incorrectly. METHODS: We define a "fiber coherence index" to describe how well fibers are connected to each other, and use it to automatically detect the correct configuration of b-vectors...
January 22, 2019: Magnetic Resonance Imaging
Yusuke Takahashi, Hidetaka Kioka, Yasunori Shintani, Akiko Ohki, Seiji Takashima, Yasushi Sakata, Takahiro Higuchi, Shigeyoshi Saito
PURPOSE: To establish a brain proton magnetic resonance spectroscopy (1 H MRS) experimental system using a mouse model of Leigh syndrome for monitoring intracerebral lactate levels as a biomarker of mitochondrial disease progression. MATERIALS AND METHODS: Brain 1 H MRS was performed in the Ndufs4 homozygous knockout (KO) mice, a mouse model of Leigh syndrome, and control mice on a horizontal 7.0-T magnetic resonance imaging system at age 5-9 weeks. In a subset of KO mice, survival analysis was performed according to the median of the intracerebral lactate levels...
January 19, 2019: Magnetic Resonance Imaging
Darío R Quiñones, Luis Miguel Fernández-Mollá, Jesús Pacheco-Torres, José M Caramés, Santiago Canals, David Moratal
INTRODUCTION: Functional magnetic resonance imaging (fMRI) is one of the most highly regarded techniques in the neuroimaging field. This technique is based on vascular responses to neuronal activation and is extensively used in clinical and animal research studies. In preclinical settings, fMRI is usually applied to anesthetized animals. However, anesthetics cause alterations, e.g. hypothermia, in the physiology of the animals and this has the potential to disrupt fMRI signals. The current temperature control method involves a technician, as well as monitoring the acquisition MRI sequences, also controlling the temperature of the animal; this is inefficient...
January 17, 2019: Magnetic Resonance Imaging
Mengmeng Yu, Mingliang Wang, Dianxu Yang, Xiaoer Wei, Wenbin Li
OBJECTIVE: The blood-brain barrier (BBB) and cerebral tissue microstructure can be impaired following traumatic brain injury (TBI). However, the spatiotemporal changes of BBB leakage and tissue microstructure are not completely understood. In this study, we evaluated the spatiotemporal changes of BBB leakage and tissue microstructure using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion kurtosis imaging (DKI) in controlled cortical impact (CCI) rats. MATERIALS AND METHODS: The DCE-MRI parameters volume transfer coefficient (Ktrans ) and DKI parameters were longitudinally measured in bilateral cortex, hippocampus, thalamus and corpus callosum (CC) at baseline (D0), acute stage (D1, D3), and subacute stage (D7, D14 and D28) post-injury...
January 17, 2019: Magnetic Resonance Imaging
Darragh E Crosbie, James Keaney, Lawrence C S Tam, W Daniel Stamer, Matthew Campbell, Peter Humphries
PURPOSE: Here, we are testing the hypothesis that dynamic contrast enhanced MRI (DCE-MRI) is a useful approach for non-invasively evaluating age-related changes in aqueous humor outflow and its contribution to elevated intraocular pressure in the DBA/2J model of pigmentary glaucoma. METHODS: A rodent-specific 7 T MRI was used to assess eye anatomy (anterior chamber (AC) and vitreous body (VB) morphology, eye size, lens size) and aqueous humor dynamics (via intravenous administration of Gd-DTPA and Gd-BOPTA contrast agents) in C57BL/6 and DBA/2J mice at 3 and 9 months of age...
January 17, 2019: Magnetic Resonance Imaging
Wenyuan Qiu, Dongxiao Li, Xinyu Jin, Fan Liu, Thanh D Nguyen, Martin R Prince, Yi Wang, Pascal Spincemaille
Liver dynamic contrast-enhanced MRI (DCE-MRI) requires high spatiotemporal resolution and large field of view to clearly visualize all relevant enhancement phases and detect early-stage liver lesions. The low-rank plus sparse (L + S) reconstruction outperforms standard sparsity-only-based reconstruction through separation of low-rank background component (L) and sparse dynamic components (S). However, the L + S decomposition is sensitive to respiratory motion so that image quality is compromised when breathing occurs during long time data acquisition...
January 15, 2019: Magnetic Resonance Imaging
Alejandro Godino-Moya, Javier Royuela-Del-Val, Muhammad Usman, Rosa-María Menchón-Lara, Marcos Martín-Fernández, Claudia Prieto, Carlos Alberola-López
PURPOSE: To analyze the impact on image quality and motion fidelity of a motion-weighted space-time variant regularization term in compressed sensing cardiac cine MRI. METHODS: k-t SPARSE-SENSE with temporal total variation (tTV) is used as the base reconstruction algorithm. Motion in the dynamic image is estimated by means of a robust registration technique for non-rigid motion. The resulting deformation fields are used to leverage the regularization term. The results are compared with standard k-t SPARSE-SENSE with tTV regularization as well as with an improved version of this algorithm that makes use of tTV and temporal Fast Fourier Transform regularization in x-f domain...
January 14, 2019: Magnetic Resonance Imaging
Gregor Körzdörfer, Josef Pfeuffer, Thomas Kluge, Matthias Gebhardt, Bernhard Hensel, Craig H Meyer, Mathias Nittka
PURPOSE: Artifacts arising from undersampling are not always treatable as incoherent noise for the pattern matching process in Magnetic Resonance Fingerprinting (MRF). To estimate the effect of undersampling artifacts on MRF quantitative results, spiral sampling trajectories and their temporal variation is examined. METHODS: The effect of sampling trajectories and their variation during the MRF experiment was assessed by characterizing aliasing artifacts. Temporal rearrangements of sampling trajectories were tested and evaluated in simulations and scans of phantoms and in a volunteer brain...
January 14, 2019: Magnetic Resonance Imaging
Yasuyuki Yamahana, Tetsuya Katsumori, Hiroshi Miura, Shunsuke Asai, Sachimi Yamada, Akiko Takahata, Kei Yamada
PURPOSE: To evaluate whether susceptibility-weighted MR imaging (SWI) findings are associated with tumor infarction on contrast-enhanced MRI (CE-MRI) after uterine artery embolization (UAE) for leiomyoma. METHODS: This was a single institution, retrospective study. Between February 2016 and April 2017, 27 consecutive patients underwent UAE and completed SWI and CE-MRI before and 1 week after UAE. Two blinded readers independently reviewed the MRI of 261 tumors ≥1 cm in all patients...
January 14, 2019: Magnetic Resonance Imaging
Paula L Croal, Jackie Leung, Charly L Phillips, Malambing G Serafin, Andrea Kassner
The purpose of this study was to compare the Infinite Cylinder and Forward Field methods of quantifying global venous oxygen saturation (Yv ) in the superior sagittal sinus (SSS) from MRI phase data, and assess their applicability in systemic cerebrovascular disease.15 children with sickle cell disease (SCD) and 10 healthy age-matched controls were imaged on a 3.0 T MRI system. Anatomical and phase data around the superior sagittal sinus were acquired from a clinically available susceptibility weighted imaging sequence and converted to Yv using the Infinite Cylinder and Forward Field methods...
January 10, 2019: Magnetic Resonance Imaging
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