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B1 mapping

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https://www.readbyqxmd.com/read/28074530/slice-profile-and-b1-corrections-in-2d-magnetic-resonance-fingerprinting
#1
Dan Ma, Simone Coppo, Yong Chen, Debra F McGivney, Yun Jiang, Shivani Pahwa, Vikas Gulani, Mark A Griswold
PURPOSE: The goal of this study is to characterize and improve the accuracy of 2D magnetic resonance fingerprinting (MRF) scans in the presence of slice profile (SP) and B1 imperfections, which are two main factors that affect quantitative results in MRF. METHODS: The SP and B1 imperfections are characterized and corrected separately. The SP effect is corrected by simulating the radiofrequency pulse in the dictionary, and the B1 is corrected by acquiring a B1 map using the Bloch-Siegert method before each scan...
January 11, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28047962/tu-h-206-03-characterizing-b1-inhomogeneities-in-dce-mri
#2
H Gach, N Mason
PURPOSE: Dynamic Contrast Enhanced (DCE) MRI is a valuable technique for measuring perfusion and permeability characteristics of tumors. Exogenous contrast concentrations are calculated based on changes in T1 measured using fast 3D gradient echo (FLASH) sequences. However, the slab selective pulses used in 3D MRI may result in B1 inhomogeneities across the volume of interest that can lead to errors in T1 and thus the estimated gadolinium concentration. We compared three FLASH DCE sequences (GRE, TWIST, and VIBE) to determine their signal homogeneity across slices and the accuracy in calculating T1 using acquisitions with variable flip angles...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047863/tu-h-206-06-b1-inhomogeneity-correction-for-measuring-t1-from-dce-mri
#3
H Gach, N Mason, H Wang, C Tsien, T Benzinger, C Robinson
PURPOSE: 3D MRI sequences typically used in DCE MRI suffer from B1 inhomogeneities associated with the slab-selective RF pulse. B1 inhomogeneities affect the calculation of tissue T1 often used to solve the two-compartment model. Previously, the inhomogeneities were corrected based on Bloch equation simulations of the RF pulse. However, the RF pulse specification may not be readily available or the simulation may not represent the actual scan conditions. The objective of this work was to directly measure B1 inhomogeneities and apply an inhomogeneity correction to minimize quantification errors in T1 fitting...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047295/tu-h-206-04-an-effective-homomorphic-unsharp-mask-filtering-method-to-correct-intensity-inhomogeneity-in-daily-treatment-mr-images
#4
D Yang, H Gach, H Li, S Mutic
PURPOSE: The daily treatment MRIs acquired on MR-IGRT systems, like diagnostic MRIs, suffer from intensity inhomogeneity issue, associated with B1 and B0 inhomogeneities. An improved homomorphic unsharp mask (HUM) filtering method, automatic and robust body segmentation, and imaging field-of-view (FOV) detection methods were developed to compute the multiplicative slow-varying correction field and correct the intensity inhomogeneity. The goal is to improve and normalize the voxel intensity so that the images could be processed more accurately by quantitative methods (e...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046531/tu-h-206-08-quantitative-impact-of-biliary-stent-artefacts-on-mr-images
#5
O Gurney-Champion, T Bruins Slot, E Lens, A van der Horst, R Klaassen, H van Laarhoven, J van Hooft, A Nederveen, A Bel
PURPOSE: Biliary stents may cause artifacts in MR-images. These artifacts are caused by differences in susceptibility (artifact-1), eddy currents during read-out (artifact-2) and eddy currents due to the excitation pulse (artifact-3), which all are MRI sequence-dependent. In this study, we investigated and quantified the magnitude of these artifacts as a function of the distance from biliary stents, using a sequence-independent approach where possible. METHODS: Eight phantoms were made containing different commercial biliary stents made of nitinol, platinol, stainless steel or polyethylene...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28044146/bloch-siegert-b1-mapping-improves-accuracy-and-precision-of-longitudinal-relaxation-measurements-in-the-breast-at-3-t
#6
Jennifer G Whisenant, Richard D Dortch, William Grissom, Hakmook Kang, Lori R Arlinghaus, Thomas E Yankeelov
Variable flip angle (VFA) sequences are a popular method of calculating T1 values, which are required in a quantitative analysis of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI). B1 inhomogeneities are substantial in the breast at 3 T, and these errors negatively impact the accuracy of the VFA approach, thus leading to large errors in the DCE-MRI parameters that could limit clinical adoption of the technique. This study evaluated the ability of Bloch-Siegert B1 mapping to improve the accuracy and precision of VFA-derived T1 measurements in the breast...
December 2016: Tomography: a Journal for Imaging Research
https://www.readbyqxmd.com/read/28011252/construction-and-modeling-of-a-reconfigurable-mri-coil-for-lowering-sar-in-patients-with-deep-brain-stimulation-implants
#7
Laleh Golestanirad, Maria Ida Iacono, Boris Keil, Leonardo M Angelone, Giorgio Bonmassar, Michael D Fox, Todd Herrington, Elfar Adalsteinsson, Cristen LaPierre, Azma Mareyam, Lawrence L Wald
Post-operative MRI of patients with deep brain simulation (DBS) implants is useful to assess complications and diagnose comorbidities, however more than one third of medical centers do not perform MRIs on this patient population due to stringent safety restrictions and liability risks. A new system of reconfigurable magnetic resonance imaging head coil composed of a rotatable linearly-polarized birdcage transmitter and a close-fitting 32-channel receive array is presented for low-SAR imaging of patients with DBS implants...
December 21, 2016: NeuroImage
https://www.readbyqxmd.com/read/28005010/simultaneous-quantitative-imaging-of-electrical-properties-and-proton-density-from-b1-maps-using-mri
#8
Jiaen Liu, Pierre-Francois Van de Moortele, Xiaotong Zhang, Yicun Wang, Bin He
Electrical conductivity and permittivity of biological tissues are important diagnostic parameters and are useful for calculating subject-specific specific absorption rate distribution. On the other hand, water proton density also has clinical relevance for diagnosis purposes. These two kinds of tissue properties are inevitably associated in the technique of electrical properties tomography (EPT), which can be used to map in vivo electrical properties based on the measured B1 field distribution at Larmor frequency using magnetic resonance imaging (MRI)...
September 2016: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/27988808/inheritance-and-quantitative-trail-loci-mapping-of-adventitious-root-numbers-in-cucumber-seedlings-under-waterlogging-conditions
#9
Xuewen Xu, Jing Ji, Qiang Xu, Xiaohua Qi, Xuehao Chen
The hypocotyl-derived adventitious root (AR) is an important morphological acclimation to waterlogging stress; however, its genetic basis has not been adequately understood. In the present study, a mixed major gene plus polygene inheritance model was used to analyze AR numbers (ARN) 7 days after waterlogging treatment in six generations (P1, P2, F1, B1, B2, and F2), using cucumber waterlogging tolerant line Zaoer-N and sensitive Pepino as parents. The results showed that the genetic model D-4, mixed one negative dominance major gene and additive-dominance polygenes, is the best-fitting genetic model for waterlogging-triggered ARN phenotype...
December 17, 2016: Molecular Genetics and Genomics: MGG
https://www.readbyqxmd.com/read/27981641/magnetic-resonance-fingerprinting-using-echo-planar-imaging-joint-quantification-of-t1-and-t2%C3%A2-relaxation-times
#10
Benedikt Rieger, Fabian Zimmer, Jascha Zapp, Sebastian Weingärtner, Lothar R Schad
PURPOSE: To develop an implementation of the magnetic resonance fingerprinting (MRF) paradigm for quantitative imaging using echo-planar imaging (EPI) for simultaneous assessment of T1 and T2∗. METHODS: The proposed MRF method (MRF-EPI) is based on the acquisition of 160 gradient-spoiled EPI images with rapid, parallel-imaging accelerated, Cartesian readout and a measurement time of 10 s per slice. Contrast variation is induced using an initial inversion pulse, and varying the flip angles, echo times, and repetition times throughout the sequence...
December 16, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27923744/simultaneous-measurement-of-total-water-content-and-myelin-water-fraction-in-brain-at-3t-using-a-t2-relaxation-based-method
#11
Sandra M Meyers, Shannon H Kolind, Alex L MacKay
PURPOSE: This work demonstrates the in vivo application of a T2 relaxation based total water content (TWC) measurement technique at 3T in healthy human brain, and evaluates accuracy using simulations that model brain tissue. The benefit of using T2 relaxation is that it provides simultaneous measurements of myelin water fraction, which correlates to myelin content. METHODS: T2 relaxation data was collected from 10 healthy human subjects with a gradient and spin echo (GRASE) sequence, along with inversion recovery for T1 mapping...
December 5, 2016: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/27913571/snord126-promotes-hcc-and-crc-cell-growth-by-activating-the-pi3k-akt-pathway-through-fgfr2
#12
Xianlong Fang, Dongmei Yang, Hongping Luo, Shuai Wu, Wenjie Dong, Jing Xiao, Sujing Yuan, Aimin Ni, Kang-Jian Zhang, Xin-Yuan Liu, Liang Chu
Small nucleolar RNA (snoRNA) dysfunctions have been associated with cancer development. SNORD126 is an orphan C/D box snoRNA that is encoded within introns 5-6 of its host gene, cyclin B1-interacting protein 1 (CCNB1IP1) The cancer-associated molecular mechanisms triggered by SNORD126 are not fully understood. Here, we demonstrate that SNORD126 is highly expressed in hepatocellular carcinoma (HCC) and colorectal cancer (CRC) patient samples. SNORD126 increased Huh-7 and SW480 cell growth and tumorigenicity in nude mice...
December 2, 2016: Journal of Molecular Cell Biology
https://www.readbyqxmd.com/read/27894742/metabolic-state-defines-the-response-of-rabbit-ovarian-cells-to-leptin
#13
Abdel Halim Harrath, Olga Østrup, Jan Rafay, Iveta Koničková Florkovičová, Jozef Laurincik, Alexander V Sirotkin
Leptin is a hormone that mediates the effect of the metabolic state on several biological functions, including reproduction. Leptin affects reproductive functions via alterations in the release of hormonal regulators. However, the extent to which caloric restriction (CR) can affect the complex processes of reproduction by other mechanisms, such as altering ovarian functions via direct binding/response to leptin, is unknown. Therefore, the aim of the present study was to show basic ovarian cell functions and CR on the response of ovarian cells to leptin...
November 25, 2016: Reproductive Biology
https://www.readbyqxmd.com/read/27825954/ultra-high-resolution-brain-metabolite-mapping-at-7-t-by-short-tr-hadamard-encoded-fid-mrsi
#14
Gilbert Hangel, Bernhard Strasser, Michal Považan, Eva Heckova, Lukas Hingerl, Roland Boubela, Stephan Gruber, Siegfried Trattnig, Wolfgang Bogner
MRSI in the brain at ≥7T is a technique of great promise, but has been limited mainly by low B0/B1(+)-homogeneity, specific absorption rate restrictions, long measurement times, and low spatial resolution. To overcome these limitations, we propose an ultra-high resolution (UHR) MRSI sequence that provides a 128×128 matrix with a nominal voxel volume of 1.7×1.7×8 mm³ in a comparatively short measurement time. A clinically feasible scan time of 10-20min is reached via a short TR of 200 ms due to an optimised free induction decay-based acquisition with shortened water suppression as well as parallel imaging (PI) using Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration (CAIPIRINHA)...
November 4, 2016: NeuroImage
https://www.readbyqxmd.com/read/27809383/ultra-high-field-rf-coil-development-for-evaluating-upper-extremity-imaging-applications
#15
Shailesh B Raval, Tiejun Zhao, Narayanan Krishnamurthy, Tales Santini, Cynthia Britton, Vijay S Gorantla, Tamer S Ibrahim
The purpose of this study is to develop and evaluate a custom-designed 7  T MRI coil and explore its use for upper extremity applications. An RF system composed of a transverse electromagnetic transmit coil and an eight-channel receive-only array was developed for 7  T upper extremity applications. The RF system was characterized and evaluated using scattering parameters and B1(+) mapping. Finite difference time domain simulations were performed to evaluate the B1(+) field distribution and specific absorption rate for the forearm region of the upper extremity...
November 3, 2016: NMR in Biomedicine
https://www.readbyqxmd.com/read/27795672/mapping-of-a-major-qtl-associated-with-protein-content-on-chromosome-2b-in-hard-red-winter-wheat-triticum-aestivum-l
#16
Yohei Terasawa, Miwako Ito, Tadashi Tabiki, Koichi Nagasawa, Koichi Hatta, Zenta Nishio
A quantitative trait locus (QTL) controlling wheat grain protein content (GPC) and flour protein content (FPC) was identified using doubled haploid (DH) lines developed from a cross between the hard red winter wheat variety 'Yumechikara' with a high protein content used for bread making, and the soft red winter wheat 'Kitahonami' with a low protein content used for Japanese white salted noodles. A single major QTL, QGpc.2B-yume, was identified on the short arm of wheat chromosome 2B for both the GPC and FPC over 3 years of testing...
September 2016: Breeding Science
https://www.readbyqxmd.com/read/27782717/quantitative-assessment-of-biliary-stent-artifacts-on-mr-images-potential-implications-for-target-delineation-in-radiotherapy
#17
Oliver J Gurney-Champion, Thijs Bruins Slot, Eelco Lens, Astrid van der Horst, Remy Klaassen, Hanneke W M van Laarhoven, Geertjan van Tienhoven, Jeanin E van Hooft, Aart J Nederveen, Arjan Bel
PURPOSE: Biliary stents may cause susceptibility artifacts, gradient-induced artifacts, and radio frequency (RF) induced artifacts on magnetic resonance images, which can hinder accurate target volume delineation in radiotherapy. In this study, the authors investigated and quantified the magnitude of these artifacts for stents of different materials. METHODS: Eight biliary stents made of nitinol, platinum-cored nitinol, stainless steel, or polyethylene from seven vendors, with different lengths (57-98 mm) and diameters (3...
October 2016: Medical Physics
https://www.readbyqxmd.com/read/27774641/high-resolution-gradient-recalled-echo-imaging-at-9-4t-using-16-channel-parallel-transmit-simultaneous-multislice-spokes-excitations-with-slice-by-slice-flip-angle-homogenization
#18
Desmond H Y Tse, Christopher J Wiggins, Benedikt A Poser
PURPOSE: In order to fully benefit from the improved signal-to-noise and contrast-to-noise ratios at 9.4T, the challenges of B1+ inhomogeneity and the long acquisition time of high-resolution 2D gradient-recalled echo (GRE) imaging were addressed. THEORY AND METHODS: Flip angle homogenized excitations were achieved by parallel transmission (pTx) of 3-spoke pulses, designed by magnitude least-squares optimization in a slice-by-slice fashion; the acquisition time reduction was achieved by simultaneous multislice (SMS) pulses...
October 23, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27759935/pulmonary-relaxometry-with-inversion-recovery-ultra-fast-steady-state-free-precession-at-1-5t
#19
Grzegorz Bauman, Francesco Santini, Orso Pusterla, Oliver Bieri
PURPOSE: To present a technique for simultaneous mapping of T1 , T2 , and relative spin density (M0 ) in human lung using inversion recovery ultra-fast steady-state free precession (IR-ufSSFP) imaging. METHODS: Pulmonary relaxometry with IR-ufSSFP is based on an interleaved time series acquisition of 2D images acquired at 1.5T. The technique was tested in a phantom and in four healthy volunteers using breath-hold and electrocardiogram triggering. Typically, 30 transient state images were acquired in a single breath-hold within < 10 s...
January 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27755746/the-effects-of-climate-downscaling-technique-and-observational-data-set-on-modeled-ecological-responses
#20
Afshin Pourmokhtarian, Charles T Driscoll, John L Campbell, Katharine Hayhoe, Anne M K Stoner
Assessments of future climate change impacts on ecosystems typically rely on multiple climate model projections, but often utilize only one downscaling approach trained on one set of observations. Here, we explore the extent to which modeled biogeochemical responses to changing climate are affected by the selection of the climate downscaling method and training observations used at the montane landscape of the Hubbard Brook Experimental Forest, New Hampshire, USA. We evaluated three downscaling methods: the delta method (or the change factor method), monthly quantile mapping (Bias Correction-Spatial Disaggregation, or BCSD), and daily quantile regression (Asynchronous Regional Regression Model, or ARRM)...
July 2016: Ecological Applications: a Publication of the Ecological Society of America
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