Geon-Ho Jahng, Mun Bae Lee, Hyung Joong Kim, Eung Je Woo, Oh-In Kwon
Diffusion weighted imaging based on random Brownian motion of water molecules within a voxel provides information on the micro-structure of biological tissues through water molecule diffusivity. As the electrical conductivity is primarily determined by the concentration and mobility of ionic charge carriers, the macroscopic electrical conductivity of biological tissues is also related to the diffusion of electrical ions. This paper aims to investigate the low-frequency electrical conductivity by relying on a pre-defined biological model that separates the brain into the intracellular (restricted) and extracellular (hindered) compartments...
October 16, 2020: NeuroImage
Chao-Chun Chang, Chia-Ying Lin, Chang-Yao Chu, Yi-Cheng Hsiung, Ming-Tsung Chuang, Yau-Lin Tseng, Yi-Ting Yen
BACKGROUND: Recent advance in tissue characterization with parametric mapping imaging has the potential to be a novel biomarker for histopathologic correlation with thymic epithelial tumors (TETs). The purpose of our study is to evaluate MRI T1 mapping with the calculation of extracellular volume (ECV) fraction for histologic correlation with thymic epithelial tumor based on lymphocyte abundance. METHODS: A retrospective study including 31 consecutive patients (14 men and 17 women, median age, 56 years; interquartile range, 12 years) with TETs was performed...
October 7, 2020: Cancer Imaging: the Official Publication of the International Cancer Imaging Society
Ghil Jona, Edna Furman-Haran, Rita Schmidt
PURPOSE: Moving to ultra-high fields (≥7 T), the inhomogeneity of both RF (B1 ) and static (B0 ) magnetic fields increases, which further motivates us to design a realistic head-shaped phantom, especially for spectroscopic imaging. Such phantoms provide images similar to the human brain and serve as a reliable tool for developing and examining methods in MRI. This study aims to develop and characterize a realistic head-shaped phantom filled with brain-mimicking metabolites for MRS and magnetic resonance spectroscopic imaging in a 7 T MRI scanner...
October 4, 2020: NMR in Biomedicine
Meeyoung Park, Chae Hwa Kwon, Hong Koo Ha, Miyeun Han, Sang Heon Song
BACKGROUND: Acute kidney injury (AKI) is defined as a sudden event of kidney failure or kidney damage within a short period. Ischemia-reperfusion injury (IRI) is a critical factor associated with severe AKI and end-stage kidney disease (ESKD). However, the biological mechanisms underlying ischemia and reperfusion are incompletely understood, owing to the complexity of these pathophysiological processes. We aimed to investigate the key biological pathways individually affected by ischemia and reperfusion at the transcriptome level...
September 25, 2020: BMC Nephrology
Kai Jiang, Yiyuan Fang, Christopher M Ferguson, Hui Tang, Prasanna K Mishra, Slobodan I Macura, Lilach O Lerman
BACKGROUND: Renal fibrosis is a common pathway in tubulointerstitial injury and a major determinant of renal insufficiency. Collagen deposition, a key feature of renal fibrosis, may serve as an imaging biomarker to differentiate scarred from healthy kidneys. PURPOSE: To test the feasibility of using quantitative magnetization transfer (qMT), which assesses tissue macromolecule content, to measure renal fibrosis. STUDY TYPE: Prospective. ANIMAL MODEL: Fifteen 129S1 mice were studied 4 weeks after either sham (n = 7) or unilateral renal artery stenosis (RAS, n = 8) surgeries...
September 17, 2020: Journal of Magnetic Resonance Imaging: JMRI
Roy A M Haast, Jonathan C Lau, Dimo Ivanov, Ravi S Menon, Kâmil Uludağ, Ali R Khan
Most neuroanatomical studies are based on T1 -weighted MR images, whose intensity profiles are not solely determined by the tissue's longitudinal relaxation times (T1 ), but also affected by varying non-T1 contributions, hampering data reproducibility. In contrast, quantitative imaging using the MP2RAGE sequence, for example, allows direct characterization of the brain based on the tissue property of interest. Combined with 7 Tesla (7T) MRI, this offers unique opportunities to obtain robust high-resolution brain data characterized by a high reproducibility, sensitivity and specificity...
September 16, 2020: NeuroImage
Yves De Deene, Morgan Wheatley, Bin Dong, Natalia F Roberts, Urszula Jelen, David Waddington, Gary P Liney
4D radiation dosimetry using a highly radiation-sensitive polymer gel dosimeter with real-time quantitative MRI readout is presented as a technique to acquire the accumulated radiation dose distribution during image guided radiotherapy (IGRT) on an MRI-Linac. Optimized T2 -weighted Turbo-Spin-Echo (TSE) scans are converted into quantitative ΔR2 maps and subsequently to radiation dose maps. The concept of temporal uncertainty is introduced as a metric of effective temporal resolution. A mathematical framework is presented to optimize the echo time of the TSE sequence in terms of dose resolution, and the trade-off between temporal resolution and dose resolution is discussed...
September 18, 2020: Physics in Medicine and Biology
Zhenxiong Wang, Mehran Shaghaghi, Shun Zhang, Guiling Zhang, Yiran Zhou, Di Wu, Zhuoli Zhang, Wenzhen Zhu, Kejia Cai
BACKGROUND: To map and quantify the proton exchange rate ( kex ) of brain tissues using improved omega plots in ischemic stroke patients and to investigate whether kex can serve as a potential endogenous surrogate imaging biomarker for detecting the metabolic state and the pathologic changes due to ischemic stroke. NEW METHOD: Three sets of Z-spectra were acquired from seventeen ischemic stroke patients using a spin echo-echo planar imaging sequence with pre-saturation chemical exchange saturation transfer (CEST) pulse at B1 of 1...
September 4, 2020: Journal of Neuroscience Methods
Naoharu Kobayashi, Ben Parkinson, Djaudat Idiyatullin, Gregor Adriany, Sebastian Theilenberg, Christoph Juchem, Michael Garwood
PURPOSE: We demonstrate the feasibility of MRI with missing-pulse steady-state free precession (MP-SSFP) in a 4T magnet with artificially degraded homogeneity. METHODS: T1 , T2 , and diffusion contrast of MP-SSFP was simulated with constant and alternate radiofrequency (RF) phase using an extended phase graph. To validate MP-SSFP performance in human brain imaging, MP-SSFP was tested with two types of artificially introduced inhomogeneous magnetic fields: (1) a pure linear gradient field, and (2) a pseudo-linear gradient field introduced by mounting a head-gradient set at 36 cm from the magnet isocenter...
September 6, 2020: Magnetic Resonance in Medicine
Ruoxun Zi, Dan Zhu, Qin Qin
PURPOSE: To develop a rapid T2 mapping protocol using optimized spiral acquisition, accelerated reconstruction, and model fitting. MATERIALS AND METHODS: A T2 -prepared stack-of-spiral gradient echo (GRE) pulse sequence was applied. A model-based approach joined with compressed sensing was compared with the two methods applied separately for accelerated reconstruction and T2 mapping. A 2-parameter-weighted fitting method was compared with 2- or 3-parameter models for accurate T2 estimation under the influences of noise and B1 inhomogeneity...
August 26, 2020: Magnetic Resonance Imaging
Louis Marage, Giulio Gambarota, Jeremy Lasbleiz, Mathieu Lederlin, Hervé Saint-Jalmes
OBJECT: The MRI tissue characterization of vertebral bone marrow includes the measurement of proton density fat fraction (PDFF), T1 and T2 * relaxation times of the water and fat components (T1W , T1F , T2 *W , T2 *F ), IVIM diffusion D, perfusion fraction f and pseudo-diffusion coefficient D*. However, the measurement of these vertebral bone marrow biomarkers (VBMBs) is affected with several confounding factors. In the current study, we investigated these confounding factors including the regional variation taking the example of variation between the anterior and posterior area in lumbar vertebrae, B1 inhomogeneity and the effect of fat suppression on f...
August 25, 2020: Magnetic Resonance Imaging
Kim L de Luca, Jop Kind
The organization of DNA within the eukaryotic nucleus is important for cellular processes such as regulation of gene expression and repair of DNA damage. To comprehend cell-to-cell variation within a complex system, systematic analysis of individual cells is necessary. While many tools exist to capture DNA conformation and chromatin context, these methods generally require large populations of cells for sufficient output. Here we describe single-cell DamID, a technique to capture contacts between DNA and a given protein of interest...
2021: Methods in Molecular Biology
Guang Yang, Xiaohong Cao, Genli Ma, Ling Qin, Yuanzhen Wu, Jian Lin, Peng Ye, Jun Yuan, Shihua Wang
Mitogen-activated protein kinase (MAPK) cascades are highly conserved in eukaryotic cells and known to play crucial roles in the regulation of various cellular processes. However, compared with kinase-mediated phosphorylation, dephosphorylation catalyzed by phosphatases has not been well characterized in filamentous fungi. In this study, we identified five MAPK pathway-related phosphatases (Msg5, Yvh1, Ptp1, Ptp2 and Oca2) and characterized their functions in Aspergillus flavus, which produces aflatoxin B1 (AFB1 ), one of the most toxic and carcinogenic secondary metabolites...
August 19, 2020: Environmental Microbiology
Maxime Yon, João P de Almeida Martins, Qingjia Bao, Matthew D Budde, Lucio Frydman, Daniel Topgaard
Diffusion tensor distribution (DTD) imaging builds on principles from diffusion, solid-state and low-field NMR spectroscopies, to quantify the contents of heterogeneous voxels as nonparametric distributions, with tensor "size", "shape" and orientation having direct relations to corresponding microstructural properties of biological tissues. The approach requires the acquisition of multiple images as a function of the magnitude, shape and direction of the diffusion-encoding gradients, leading to long acquisition times unless fast image read-out techniques like EPI are employed...
August 19, 2020: NMR in Biomedicine
Paul Soullié, Alexia Missoffe, Khalid Ambarki, Jacques Felblinger, Freddy Odille
PURPOSE: To develop a fast and easy-to-use electrical properties tomography (EPT) method based on a single MR scan, avoiding both the need of a B1 -map and transceive phase assumption, and that is robust against noise. THEORY: Derived from Maxwell's equations, conductivity, and permittivity are reconstructed from a new partial differential equation involving the product of the RF fields and its derivatives. This also allows us to clarify and revisit the relevance of common assumptions of MREPT...
August 11, 2020: Magnetic Resonance in Medicine
Anne-Claire Langlois, Giulia Manzoni, Laetitia Vincensini, Romain Coppée, Carine Marinach, Maryse Guérin, Thierry Huby, Véronique Carrière, François-Loïc Cosset, Marlène Dreux, Eric Rubinstein, Olivier Silvie
Sporozoite forms of the Plasmodium parasite, the causative agent of malaria, are transmitted by mosquitoes and first infect the liver for an initial round of replication before parasite proliferation in the blood. The molecular mechanisms involved during sporozoite invasion of hepatocytes remain poorly understood. Two receptors of the Hepatitis C virus (HCV), the tetraspanin CD81 and the scavenger receptor class B type 1 (SR-B1), play an important role during the entry of Plasmodium sporozoites into hepatocytes...
August 11, 2020: Scientific Reports
Mohammad Altamish, Rajiv Dahiya, Avinash Kumar Singh, Anurag Mishra, Alaa A A Aljabali, Saurabh Satija, Meenu Mehta, Harish Dureja, Parteek Prasher, Poonam Negi, Deepak N Kapoor, Rohit Goyal, Murtaza M Tambuwala, Dinesh Kumar Chellappan, Kamal Dua, Gaurav Gupta
Peutz-Jeghers syndrome (PJS) is a well-described inherited syndrome, characterized by the development of gastrointestinal polyps and characteristic mucocutaneous freckling. PJS is an autosomal prevailing disease, due to genetic mutation on chromosome 19p, manifested by restricted mucocutaneous melanosis in association with gastrointestinal (GI) polyposis. The gene for PJS has recently been shown to be a serine/threonine kinase, known as LKB1 or STK11, which maps to chromosome subband 19p13.3. This gene has a putative coding region of 1302 bp, divided into nine exons, and acts as a tumor suppressor in the hamartomatous polyps of PJS patients and in the other neoplasms that develop in PJS patients...
2020: Critical Reviews in Eukaryotic Gene Expression
Omer F Oran, L Martyn Klassen, Kyle M Gilbert, Joseph S Gati, Ravi S Menon
The magnetization-prepared two-rapid-gradient-echo (MP2RAGE) sequence is used for structural T1 -weighted imaging and T1 mapping of the human brain. In this sequence, adiabatic inversion RF pulses are commonly used, which require the B1 + magnitude to be above a certain threshold. Achieving this threshold in the whole brain may not be possible at ultra-high fields because of the short RF wavelength. This results in low-inversion regions especially in the inferior brain (eg cerebellum and temporal lobes), which is reflected as regions of bright signal in MP2RAGE images...
August 4, 2020: NMR in Biomedicine
Michael A Ohliger, Jeremy W Gordon, Lucas Carvajal, Peder E Z Larson, Jao J Ou, Shubhangi Agarwal, Zihan Zhu, Daniel B Vigneron, Cornelius von Morze
PURPOSE: To use fiducial markers containing manganese 55 to rapidly localize carbon 13 (13 C) RF coils for correcting images for B1 variation. METHODS: Hollow high-density polyethylene spheres were filled with 3M sodium permanganate and affixed to a rectangular 13 C-tuned RF coil. The relative positions of the markers and coil conductors were mapped using CT. Marker positions were measured by MRI using a series of 1D projections and automated peak detection. Once the coil location was determined, coil sensitivity was estimated using a quasi-static calculation...
August 1, 2020: Magnetic Resonance in Medicine
C Cabezas, C Bermúdez, B Tercero, J Cernicharo
Context: Sulfur-containing molecules constitute only 8% of the molecules observed in the interstellar medium (ISM), in spite of the fact that sulfur has been shown to be an abundant element in the ISM. In order to understand the chemical behavior of the ISM and specific cases like the missing sulfur reservoir, a detailed chemical molecular composition in the ISM must be mapped out. Aims: Our goal is to investigate the rotational spectrum of ethyl methyl sulfide, CH3 CH2 SCH3 , which ms to be a potential candidate for observation in the ISM since the simpler analogs, CH3 SH and CH3 CH2 SH, have already been detected...
July 2020: Astronomy and Astrophysics
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