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B1 mapping

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https://www.readbyqxmd.com/read/29159883/phase-sensitive-b1-mapping-effects-of-relaxation-and-rf-spoiling
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
https://www.readbyqxmd.com/read/28994132/fast-and-accurate-multi-channel-b1-mapping-based-on-the-tiamo-technique-for-7t-uhf-body-mri
#10
Sascha Brunheim, Marcel Gratz, Sören Johst, Andreas K Bitz, Thomas M Fiedler, Mark E Ladd, Harald H Quick, Stephan Orzada
PURPOSE: Current methods for mitigation of transmit field B1+ inhomogeneities at ultrahigh field (UHF) MRI by multi-channel radiofrequency (RF) shimming rely on accurate B1+ mapping. This can be time consuming when many RF channels have to be mapped for in vivo body MRI, where the B1 maps should ideally be acquired within a single breath-hold. Therefore, a new B1+ mapping technique (B1TIAMO) is proposed. METHODS: The performance of this technique is validated against an established method (DREAM) in phantom measurements for a cylindrical head phantom with an 8-channel transmit/receive (Tx/Rx) array...
October 9, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28986653/pool-size-ratio-of-the-substantia-nigra-in-parkinson-s-disease-derived-from-two-different-quantitative-magnetization-transfer-approaches
#11
Paula Trujillo, Paul E Summers, Alex K Smith, Seth A Smith, Luca T Mainardi, Sergio Cerutti, Daniel O Claassen, Antonella Costa
PURPOSE: We sought to measure quantitative magnetization transfer (qMT) properties of the substantia nigra pars compacta (SNc) in patients with Parkinson's disease (PD) and healthy controls (HCs) using a full qMT analysis and determine whether a rapid single-point measurement yields equivalent results for pool size ratio (PSR). METHODS: Sixteen different MT-prepared MRI scans were obtained at 3 T from 16 PD patients and eight HCs, along with B1, B0, and relaxation time maps...
December 2017: Neuroradiology
https://www.readbyqxmd.com/read/28949040/a-modern-green-revolution-gene-for-reduced-height-in-wheat
#12
Tobias Würschum, Simon M Langer, C Friedrich H Longin, Matthew R Tucker, Willmar L Leiser
Increases in the yield of wheat during the Green Revolution of the late 20(th) century were achieved through the introduction of Reduced height (Rht) dwarfing genes. The Rht-B1 and Rht-D1 loci ensured short stature by limiting the response to the growth-promoting hormone gibberellin, and are now widespread through international breeding programs. Despite this advantage, interference with the plant's response to gibberellin also triggers adverse effects for a range of important agronomic traits, and consequently modern Green Revolution genes are urgently required...
September 26, 2017: Plant Journal: for Cell and Molecular Biology
https://www.readbyqxmd.com/read/28944190/analysis-of-proteomic-differences-between-liquefied-after-cataracts-and-normal-lenses-using-two-dimensional-gel-electrophoresis-and-mass-spectrometry
#13
Jia-Jia Ge, Yu-Sen Huang
AIM: To analyze and identify the proteomic differences between liquefied after-cataracts and normal lenses by means of liquefied chromatography-tandem mass spectrometry (LC-MS/MS). METHODS: Three normal lenses and three liquefied after-cataracts were exposed to depolymerizing reagents to extract the total proteins. Protein concentrations were separated using two-dimensional gel electrophoresis (2-DE). The digitized images obtained with a GS-800 scanner were then analyzed with PDQuest7...
2017: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/28922760/the-roles-of-pleiotropy-and-close-linkage-as-revealed-by-association-mapping-of-yield-and-correlated-traits-of-wheat-triticum-aestivum-l
#14
Albert W Schulthess, Jochen C Reif, Jie Ling, Jörg Plieske, Sonja Kollers, Erhard Ebmeyer, Viktor Korzun, Odile Argillier, Gunther Stiewe, Martin W Ganal, Marion S Röder, Yong Jiang
Grain yield (GY) of bread wheat (Triticum aestivum L.) is quantitatively inherited. Correlated GY-syndrome traits such as plant height (PH), heading date (HD), thousand grain weight (TGW), test weight (TW), grains per ear (GPE), and ear weight (EW) influence GY. Most quantitative genetics studies assessed the multiple-trait (MT) complex of GY-syndrome using single-trait approaches, and little is known about its underlying pleiotropic architecture. We investigated the pleiotropic architecture of wheat GY-syndrome through MT association mapping (MT-GWAS) using 372 varieties phenotyped in up to eight environments and genotyped with 18 832 single nucleotide polymorphisms plus 24 polymorphic functional markers...
July 10, 2017: Journal of Experimental Botany
https://www.readbyqxmd.com/read/28913930/accuracy-repeatability-and-interplatform-reproducibility-of-t1-quantification-methods-used-for-dce-mri-results-from-a-multicenter-phantom-study
#15
Octavia Bane, Stefanie J Hectors, Mathilde Wagner, Lori L Arlinghaus, Madhava P Aryal, Yue Cao, Thomas L Chenevert, Fiona Fennessy, Wei Huang, Nola M Hylton, Jayashree Kalpathy-Cramer, Kathryn E Keenan, Dariya I Malyarenko, Robert V Mulkern, David C Newitt, Stephen E Russek, Karl F Stupic, Alina Tudorica, Lisa J Wilmes, Thomas E Yankeelov, Yi-Fei Yen, Michael A Boss, Bachir Taouli
PURPOSE: To determine the in vitro accuracy, test-retest repeatability, and interplatform reproducibility of T1 quantification protocols used for dynamic contrast-enhanced MRI at 1.5 and 3 T. METHODS: A T1 phantom with 14 samples was imaged at eight centers with a common inversion-recovery spin-echo (IR-SE) protocol and a variable flip angle (VFA) protocol using seven flip angles, as well as site-specific protocols (VFA with different flip angles, variable repetition time, proton density, and Look-Locker inversion recovery)...
September 14, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28893660/a-new-rf-transmit-coil-for-foot-and-ankle-imaging-at-7t-mri
#16
Tales Santini, Junghwan Kim, Sossena Wood, Narayanan Krishnamurthy, Nadim Farhat, Carlos Maciel, Shailesh Raval, Tiejun Zhao, Tamer S Ibrahim
A four-channel Tic-Tac-Toe (TTT) transmit RF coil was designed and constructed for foot and ankle imaging at 7T MRI. Numerical simulations using an in-house developed FDTD package and experimental analyses using a homogenous phantom show an excellent agreement in terms of B1(+) field distribution and s-parameters. Simulations performed on an anatomically detailed human lower leg model demonstrated an B1(+) field distribution with a coefficient of variation (CV) of 23.9%/15.6%/28.8% and average B1(+) of 0.33μT/0...
September 8, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28856778/temporally-resolved-parametric-assessment-of-z-magnetization-recovery-topaz-dynamic-myocardial-t1-mapping-using-a-cine-steady-state-look-locker-approach
#17
Sebastian Weingärtner, Chetan Shenoy, Benedikt Rieger, Lothar R Schad, Jeanette Schulz-Menger, Mehmet Akçakaya
PURPOSE: To develop and evaluate a cardiac phase-resolved myocardial T1 mapping sequence. METHODS: The proposed method for temporally resolved parametric assessment of Z-magnetization recovery (TOPAZ) is based on contiguous fast low-angle shot imaging readout after magnetization inversion from the pulsed steady state. Thereby, segmented k-space data are acquired over multiple heartbeats, before reaching steady state. This results in sampling of the inversion-recovery curve for each heart phase at multiple points separated by an R-R interval...
August 30, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28855282/discovery-of-a-novel-stem-rust-resistance-allele-in-durum-wheat-that-exhibits-differential-reactions-to-ug99-isolates
#18
Jayaveeramuthu Nirmala, Jyoti Saini, Maria Newcomb, Pablo Olivera, Sam Gale, Daryl Klindworth, Elias Elias, Luther Talbert, Shiaoman Chao, Justin Faris, Steven Xu, Yue Jin, Matthew N Rouse
Wheat stem rust, caused by Puccinia graminis f. sp. tritici Eriks. & E. Henn, can incur yield losses in susceptible cultivars of durum wheat, Triticum turgidum ssp. durum (Desf.) Husnot. Although several durum cultivars possess the stem rust resistance gene Sr13, additional genes in durum wheat effective against emerging virulent races have not been described. Durum line 8155-B1 confers resistance against the P. graminis f. sp. tritici race TTKST, the variant race of the Ug99 race group with additional virulence to wheat stem rust resistance gene Sr24 However, 8155-B1 does not confer resistance to the first-described race in the Ug99 race group: TTKSK...
October 5, 2017: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/28845431/mapping-qtl-for-root-and-shoot-morphological-traits-in-a-durum-wheat%C3%A2-%C3%A3-%C3%A2-t-dicoccum-segregating-population-at-seedling-stage
#19
Anna Iannucci, Daniela Marone, Maria Anna Russo, Pasquale De Vita, Vito Miullo, Pina Ferragonio, Antonio Blanco, Agata Gadaleta, Anna Maria Mastrangelo
A segregating population of 136 recombinant inbred lines derived from a cross between the durum wheat cv. "Simeto" and the T. dicoccum accession "Molise Colli" was grown in soil and evaluated for a number of shoot and root morphological traits. A total of 17 quantitative trait loci (QTL) were identified for shoot dry weight, number of culms, and plant height and for root dry weight, volume, length, surface area, and number of forks and tips, on chromosomes 1B, 2A, 3A, 4B, 5B, 6A, 6B, and 7B. LODs were 2.1 to 21...
2017: International Journal of Genomics
https://www.readbyqxmd.com/read/28833436/fast-3d-magnetic-resonance-fingerprinting-for-a-whole-brain-coverage
#20
Dan Ma, Yun Jiang, Yong Chen, Debra McGivney, Bhairav Mehta, Vikas Gulani, Mark Griswold
PURPOSE: The purpose of this study was to accelerate the acquisition and reconstruction time of 3D magnetic resonance fingerprinting scans. METHODS: A 3D magnetic resonance fingerprinting scan was accelerated by using a single-shot spiral trajectory with an undersampling factor of 48 in the x-y plane, and an interleaved sampling pattern with an undersampling factor of 3 through plane. Further acceleration came from reducing the waiting time between neighboring partitions...
August 22, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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