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B1 mapping

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https://www.readbyqxmd.com/read/29322233/high-isotropic-resolution-t2-mapping-of-the-lumbosacral-plexus-with-t2-prepared-3d-turbo-spin-echo
#1
Nico Sollmann, Dominik Weidlich, Barbara Cervantes, Elisabeth Klupp, Carl Ganter, Hendrik Kooijman, Ernst J Rummeny, Claus Zimmer, Jan S Kirschke, Dimitrios C Karampinos
PURPOSE: Isotropic high-resolution three-dimensional (3D) magnetic resonance neurography (MRN) is increasingly used to depict even small and highly oblique nerves of the lumbosacral plexus (LSP). The present study introduces a T2 mapping sequence (T2-prepared 3D turbo spin echo) that is B1-insensitive and enables quantitative assessment of LSP nerves. METHODS: In this study 15 healthy subjects (mean age 28.5 ± 3.8 years) underwent 3 T MRN of the LSP area three times...
January 10, 2018: Clinical Neuroradiology
https://www.readbyqxmd.com/read/29314235/accurate-t1-mapping-of-short-t2-tissues-using-a-three-dimensional-ultrashort-echo-time-cones-actual-flip-angle-imaging-variable-repetition-time-3d-ute-cones-afi-vtr-method
#2
Ya-Jun Ma, Xing Lu, Michael Carl, Yanchun Zhu, Nikolaus M Szeverenyi, Graeme M Bydder, Eric Y Chang, Jiang Du
PURPOSE: To develop an accurate T1 measurement method for short T2 tissues using a combination of a 3-dimensional ultrashort echo time cones actual flip angle imaging technique and a variable repetition time technique (3D UTE-Cones AFI-VTR) on a clinical 3T scanner. METHODS: First, the longitudinal magnetization mapping function of the excitation pulse was obtained with the 3D UTE-Cones AFI method, which provided information about excitation efficiency and B1 inhomogeneity...
January 3, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29280211/radial-magnetic-resonance-imaging-mri-using-a-rotating-radiofrequency-rf-coil-at-9-4%C3%A2-t
#3
Mingyan Li, Ewald Weber, Jin Jin, Thimo Hugger, Yasvir Tesiram, Peter Ullmann, Simon Stark, Miguel Fuentes, Sven Junge, Feng Liu, Stuart Crozier
The rotating radiofrequency coil (RRFC) has been developed recently as an alternative approach to multi-channel phased-array coils. The single-element RRFC avoids inter-channel coupling and allows a larger coil element with better B1 field penetration when compared with an array counterpart. However, dedicated image reconstruction algorithms require accurate estimation of temporally varying coil sensitivities to remove artefacts caused by coil rotation. Various methods have been developed to estimate unknown sensitivity profiles from a few experimentally measured sensitivity maps, but these methods become problematic when the RRFC is used as a transceiver coil...
December 27, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/29278766/phase-unwinding-for-dictionary-compression-with-multiple-channel-transmission-in-magnetic-resonance-fingerprinting
#4
Riccardo Lattanzi, Bei Zhang, Florian Knoll, Jakob Assländer, Martijn A Cloos
PURPOSE: Magnetic Resonance Fingerprinting reconstructions can become computationally intractable with multiple transmit channels, if the B1+ phases are included in the dictionary. We describe a general method that allows to omit the transmit phases. We show that this enables straightforward implementation of dictionary compression to further reduce the problem dimensionality. METHODS: We merged the raw data of each RF source into a single k-space dataset, extracted the transceiver phases from the corresponding reconstructed images and used them to unwind the phase in each time frame...
December 23, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29276996/b1-control-receive-array-coil-b-rac-for-reducing-b1-inhomogeneity-in-abdominal-imaging-at-3t-mri
#5
Yukio Kaneko, Yoshihisa Soutome, Hideta Habara, Yoshitaka Bito, Hisaaki Ochi
B1+ inhomogeneity in the human body increases as the nuclear magnetic resonance (NMR) frequency increases. Various methods have thus been developed to reduce B1+ inhomogeneity, such as a dielectric pad, a coupling coil, parallel transmit, and radio-frequency (RF) shimming. However, B1+ inhomogeneity still remains in some cases of abdominal imaging. In this study, we developed a B1-control receive array coil (B-RAC). Unlike the conventional receive array coil, B-RAC reduces B1+ inhomogeneity by using additional PIN diodes to generate the inductive loop during the RF transmit period...
December 14, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/29260882/histogram-analysis-of-apparent-diffusion-coefficient-maps-for-assessing-thymic-epithelial-tumors-correlation-with-world-health-organization-classification-and-clinical-staging
#6
Ling-Yan Kong, Wei Zhang, Yue Zhou, Hai Xu, Hai-Bin Shi, Qing Feng, Xiao-Quan Xu, Tong-Fu Yu
OBJECTIVE: To investigate the value of apparent diffusion coefficients (ADC) histogram analysis for assessing World Health Organization (WHO) pathological classification and Masaoka clinical stages of thymic epithelial tumors. METHODS: Thirty-seven patients with histologically confirmed thymic epithelial tumors were enrolled. ADC measurements were performed using hot-spot ROI (ADCHS-ROI) and histogram-based approach. ADC histogram parameters included mean ADC (ADCmean), median ADC (ADCmedian), 10 and 90 percentile of ADC (ADC10 and ADC90), kurtosis and skewness...
December 20, 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/29250080/molecular-diversity-analysis-and-genetic-mapping-of-pod-shatter-resistance-loci-in-brassica-carinata-l
#7
Rosy Raman, Yu Qiu, Neil Coombes, Jie Song, Andrzej Kilian, Harsh Raman
Seed lost due to easy pod dehiscence at maturity (pod shatter) is a major problem in several members of Brassicaceae family. We investigated the level of pod shatter resistance in Ethiopian mustard (Brassica carinata) and identified quantitative trait loci (QTL) for targeted introgression of this trait in Ethiopian mustard and its close relatives of the genus Brassica. A set of 83 accessions of B. carinata, collected from the Australian Grains Genebank, was evaluated for pod shatter resistance based on pod rupture energy (RE)...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/29205623/improvement-of-the-repeatability-of-parallel-transmission-at-7t-using-interleaved-acquisition-in-the-calibration-scan
#8
Hiroyuki Kameda, Kohsuke Kudo, Tsuyoshi Matsuda, Taisuke Harada, Yuji Iwadate, Ikuko Uwano, Fumio Yamashita, Kunihiro Yoshioka, Makoto Sasaki, Hiroki Shirato
BACKGROUND: Respiration-induced phase shift affects B0 /B1+ mapping repeatability in parallel transmission (pTx) calibration for 7T brain MRI, but is improved by breath-holding (BH). However, BH cannot be applied during long scans. PURPOSE: To examine whether interleaved acquisition during calibration scanning could improve pTx repeatability and image homogeneity. STUDY TYPE: Prospective. SUBJECTS: Nine healthy subjects...
December 4, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/29197390/evaluation-of-b1-inhomogeneity-effect-on-dce-mri-data-analysis-of-brain-tumor-patients-at-3t
#9
Anirban Sengupta, Rakesh Kumar Gupta, Anup Singh
BACKGROUND: Dynamic-contrast-enhanced (DCE) MRI data acquired using gradient echo based sequences is affected by errors in flip angle (FA) due to transmit B1 inhomogeneity (B1inh). The purpose of the study was to evaluate the effect of B1inh on quantitative analysis of DCE-MRI data of human brain tumor patients and to evaluate the clinical significance of B1inh correction of perfusion parameters (PPs) on tumor grading. METHODS: An MRI study was conducted on 35 glioma patients at 3T...
December 2, 2017: Journal of Translational Medicine
https://www.readbyqxmd.com/read/29194732/doppler-ultrasound-triggering-for-cardiac-mri-at-7t
#10
F Kording, C Ruprecht, B Schoennagel, K Fehrs, J Yamamura, G Adam, J Goebel, K Nassenstein, S Maderwald, H H Quick, O Kraff
PURPOSE: A prerequisite for cardiac MR (CMR) imaging is adequate synchronization of image acquisition with the cardiac cycle. Electrocardiogram triggering may be hampered by electromagnetic interferences at high field strength. The purpose of this work is to evaluate the feasibility of Doppler ultrasound triggering for CMR image synchronization at 7T ultra-high-field MRI. METHODS: A custom-built Doppler ultrasound (DUS) trigger device was developed. Magnetic resonance compatibility was evaluated using E- and H-field probes and flip angle maps prior to the study...
December 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29188438/mapping-causal-mutations-by-exome-sequencing-in-a-wheat-tilling-population-a-tall-mutant-case-study
#11
Youngjun Mo, Tyson Howell, Hans Vasquez-Gross, Luis Alejandro de Haro, Jorge Dubcovsky, Stephen Pearce
Forward genetic screens of induced mutant plant populations are powerful tools to identify genes underlying phenotypes of interest. Using traditional techniques, mapping causative mutations from forward screens is a lengthy, multi-step process, requiring the identification of a broad genetic region followed by candidate gene sequencing to characterize the causal variant. Mapping by whole genome sequencing accelerates the identification of causal mutations by simultaneously defining a mapping region and providing information on the induced genetic variants...
November 29, 2017: Molecular Genetics and Genomics: MGG
https://www.readbyqxmd.com/read/29159883/phase-sensitive-b1-mapping-effects-of-relaxation-and-rf-spoiling
#12
Jie Wen, Alexander L Sukstanskii, Dmitriy A Yablonskiy
PURPOSE: To develop a phase-based B1 mapping technique accounting for the effects of imperfect RF spoiling and magnetization relaxation. THEORY AND METHODS: The technique is based on a multi-gradient-echo sequence with 2 successive orthogonal radiofrequency (RF) excitation pulses followed by the train of gradient echoes measurements. We have derived a theoretical expression relating the MR signal phase produced by the 2 successive RF pulses to the B1 field and B0 -related frequency shift...
November 20, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29159855/b1-artifact-reduction-in-abdominal-dce-mri-using-kt-points-first-clinical-assessment-of-dynamic-rf-shimming-at-3t
#13
Raphaël Tomi-Tricot, Vincent Gras, Franck Mauconduit, François Legou, Nicolas Boulant, Matthias Gebhardt, Dieter Ritter, Berthold Kiefer, Pierre Zerbib, Alain Rahmouni, Alexandre Vignaud, Alain Luciani, Alexis Amadon
BACKGROUND: The excitation inhomogeneity artifact occurring at 3T in the abdomen can lead to dramatic loss of signal and contrast, thereby hampering diagnosis. PURPOSE: To assess excitation homogeneity and image quality achieved by nonselective prototypical kT -points pulses, compared to tailored static RF shimming, in clinical routine on a commercial dual-transmit scanner. STUDY TYPE: Retrospective study with Institutional Review Board approval; informed consent was waived...
November 21, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/29146906/qtl-mapping-and-molecular-characterization-of-the-classical-d-locus-controlling-seed-and-flower-color-in-linum-usitatissimum-flax
#14
Gurudatt Pavagada Sudarshan, Manoj Kulkarni, Leonid Akhov, Paula Ashe, Hamid Shaterian, Sylvie Cloutier, Gordon Rowland, Yangdou Wei, Gopalan Selvaraj
The flowers of flax (linseed) are blue-hued, ephemeral and self-pollinating, and the seeds are typically brown. A century-old interest in natural yellow seed variants and a historical model point to recessive alleles in B1, D and G loci being responsible, but the functional aspects had remained unknown. Here, we characterized the "D" locus by quantitative trait loci (QTL) mapping and identified a FLAVONOID 3'5' HYDROXYLASE (F3'5'H) gene therein. It does not belong to the F3'5'H clade, but resembles biochemically characterized F3'Hs (flavonoid 3' hydroxylase) but without F3'H activity...
November 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29121111/genetic-and-physical-mapping-of-anther-extrusion-in-elite-european-winter-wheat
#15
Quddoos H Muqaddasi, Klaus Pillen, Jörg Plieske, Martin W Ganal, Marion S Röder
The production and cultivation of hybrid wheat is a possible strategy to close the yield gap in wheat. Efficient hybrid wheat seed production largely depends on high rates of cross-pollination which can be ensured through high anther extrusion (AE) by male parental lines. Here, we report the AE capacity and elucidate its genetics in 514 elite European winter wheat varieties via genome-wide association studies (GWAS). We observed a wide range of variation among genotypes and a high heritability (0.80) for AE...
2017: PloS One
https://www.readbyqxmd.com/read/29118306/quantitation-error-in-1-h-mrs-caused-by-b1-inhomogeneity-and-chemical-shift-displacement
#16
Hidehiro Watanabe, Nobuhiro Takaya
PURPOSE: The quantitation accuracy in proton magnetic resonance spectroscopy ((1)H MRS) improves at higher B0 field. However, a larger chemical shift displacement (CSD) and stronger B1 inhomogeneity exist. In this work, we evaluate the quantitation accuracy for the spectra of metabolite mixtures in phantom experiments at 4.7T. We demonstrate a position-dependent error in quantitation and propose a correction method by measuring water signals. MATERIALS AND METHODS: All experiments were conducted on a whole-body 4...
November 8, 2017: Magnetic Resonance in Medical Sciences: MRMS
https://www.readbyqxmd.com/read/29100988/fast-b1-mapping-using-three-consecutive-rf-pulses-and-balanced-gradients-for-improved-bssfp-imaging
#17
Min-Oh Kim, Taehwa Hong, Dong-Hyun Kim
PURPOSE: To develop a B1(+) mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1(+) inhomogeneity compensation. METHODS: Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1(+)) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1(+) was estimated using the two magnitude images and bSSFP data was sequentially acquired...
October 31, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29073228/using-a-whole-body-31p-birdcage-transmit-coil-and-16-element-receive-array-for-human-cardiac-metabolic-imaging-at-7t
#18
Ladislav Valkovič, Iulius Dragonu, Salam Almujayyaz, Alex Batzakis, Liam A J Young, Lucian A B Purvis, William T Clarke, Tobias Wichmann, Titus Lanz, Stefan Neubauer, Matthew D Robson, Dennis W J Klomp, Christopher T Rodgers
PURPOSE: Cardiac phosphorus magnetic resonance spectroscopy (31P-MRS) provides unique insight into the mechanisms of heart failure. Yet, clinical applications have been hindered by the restricted sensitivity of the surface radiofrequency-coils normally used. These permit the analysis of spectra only from the interventricular septum, or large volumes of myocardium, which may not be meaningful in focal disease. Löring et al. recently presented a prototype whole-body (52 cm diameter) transmit/receive birdcage coil for 31P at 7T...
2017: PloS One
https://www.readbyqxmd.com/read/29061370/strategically-acquired-gradient-echo-stage-imaging-part-ii-correcting-for-rf-inhomogeneities-in-estimating-t1-and-proton-density
#19
Yu Wang, Yongsheng Chen, Dongmei Wu, Ying Wang, Sean K Sethi, Guang Yang, Haibin Xie, Shuang Xia, E Mark Haacke
PURPOSE: To develop a method for mapping the B1 transmit (B1t) and B1 receive (B1r) fields from two gradient echo datasets each with a different flip angle and from these two images obtain accurate T1 and proton density (PD) maps of the brain. METHODS: A strategically acquired gradient echo (STAGE) data set is collected using two flip angles each with multiple echoes. The B1t field extraction was based on forcing cortical gray matter and white matter to have specific T1 values and fitting the resulting B1t field to a quadratic function...
October 20, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29036451/genetic-mapping-and-phylogenetic-analysis-reveal-intraspecific-variation-in-sex-chromosomes-of-the-virginian-strawberry
#20
Na Wei, Rajanikanth Govindarajulu, Jacob A Tennessen, Aaron Liston, Tia-Lynn Ashman, Melissa Wilson Sayres
With their extraordinary diversity in sexual systems, flowering plants offer unparalleled opportunities to understand sex determination and to reveal generalities in the evolution of sex chromosomes. Comparative genetic mapping of related taxa with good phylogenetic resolution can delineate the extent of sex chromosome diversity within plant groups, and lead the way to understanding the evolutionary drivers of such diversity. The North American octoploid wild strawberries provide such an opportunity. We performed linkage mapping using targeted sequence capture for the subdioecious western Fragaria virginiana ssp...
October 30, 2017: Journal of Heredity
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