Read by QxMD icon Read

B1 mapping

Xinran Zhong, Thomas Martin, Holden H Wu, Krishna S Nayak, Kyunghyun Sung
PURPOSE: To develop and evaluate a practical B1+ correction method for prostate dynamic contrast-enhanced (DCE) MRI analysis. THEORY: We proposed a simple analytical B1+ correction method using a Taylor series approximation to the steady-state spoiled gradient echo signal equation. This approach only requires B1+ maps and uncorrected pharmacokinetic (PK) parameters as input to estimate the corrected PK parameters. METHODS: The proposed method was evaluated using a prostate digital reference object (DRO), and 82 in vivo prostate DCE-MRI cases...
May 16, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Pernilla Peterson, Carl Johan Tiderius, Emma Olsson, Björn Lundin, Lars E Olsson, Jonas Svensson
BACKGROUND: dGEMRIC (delayed Gadolinium Enhanced Magnetic Resonance Image of Cartilage) is a well-established technique for cartilage quality assessment in osteoarthritis at clinical field strengths. The method is robust, but requires injection of contrast agent and a cumbersome examination procedure. New non-contrast-agent-based techniques for cartilage quality assessment are currently being developed at 7 T. However, dGEMRIC remains an important reference technique during this development...
May 16, 2018: BMC Musculoskeletal Disorders
Dushyant Kumar, Hari Hariharan, Tobias D Faizy, Patrick Borchert, Susanne Siemonsen, Jens Fiehler, Ravinder Reddy, Jan Sedlacik
PURPOSE: We present a computationally feasible and iterative multi-voxel spatially regularized algorithm for myelin water fraction (MWF) reconstruction. This method utilizes 3D spatial correlations present in anatomical/pathological tissues and underlying B1+ -inhomogeneity or flip angle inhomogeneity to enhance the noise robustness of the reconstruction while intrinsically accounting for stimulated echo contributions using T2-distribution data alone. METHODS: Simulated data and in vivo data acquired using 3D non-selective multi-echo spin echo (3DNS-MESE) were used to compare the reconstruction quality of the proposed approach against those of the popular algorithm (the method by Prasloski et al...
May 12, 2018: NeuroImage
O Togao, A Hiwatashi, T Wada, K Yamashita, K Kikuchi, C Tokunaga, J Keupp, M Yoneyama, H Honda
BACKGROUND AND PURPOSE: Glycosaminoglycan chemical exchange saturation transfer (gagCEST) imaging allows the direct measurement and mapping of glycosaminoglycans. In this study, we aimed to evaluate the usefulness of gagCEST imaging in the quantitative assessment of intervertebral disc degeneration in a comparison with Pfirrmann grade and T1-ρ measurements. MATERIALS AND METHODS: Ninety-six lumbar intervertebral discs in 24 volunteers (36.0 ± 8.5 years of age, 21 men and 3 women) were examined with both gagCEST imaging and T1-ρ measurements...
May 10, 2018: AJNR. American Journal of Neuroradiology
Ronald Mooiweer, Alessandro Sbrizzi, Alexander J E Raaijmakers, Cornelis A T van den Berg, Peter R Luijten, Hans Hoogduin
A method is described to design parallel transmit (PTX) excitation pulses that are compatible with turbo spin echo (TSE) sequences, based on information available from conventional per-channel B1 + mapping. The excitation phase of PTX pulses that generate a reduced field of excitation (rFOX) is matched to the phase the quadrature mode of a PTX coil. This enables TSE imaging of a PTX-enabled rFOX excitation combined with standard nonselective refocusing pulses transmitted in the quadrature mode. In-vivo imaging experiments were performed at 7T using a dual channel parallel transmit head coil...
May 7, 2018: Magnetic Resonance Imaging
Mathieu Boudreau, G Bruce Pike
PURPOSE: To develop and validate a regularization approach of optimizing B1 insensitivity of the quantitative magnetization transfer (qMT) pool-size ratio (F). METHODS: An expression describing the impact of B1 inaccuracies on qMT fitting parameters was derived using a sensitivity analysis. To simultaneously optimize for robustness against noise and B1 inaccuracies, the optimization condition was defined as the Cramér-Rao lower bound (CRLB) regularized by the B1 -sensitivity expression for the parameter of interest (F)...
May 7, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Bo Ram Kim, Ji Soo Song, Eun Jung Choi, Seung Bae Hwang, Hong Pil Hwang
Objective: To compare apparent diffusion coefficient (ADC) of the upper abdominal organs acquired with multiple b-value combinations and to investigate usefulness of normalization. Materials and Methods: We retrospectively analyzed data, including 3T diffusion-weighted images, of 100 patients (56 men, 44 women; mean age, 63.9) that underwent liver magnetic resonance imaging. An ADC map was derived with the following six b-value combinations: b1 = 0, 50, 400, 800; b2 = 0, 800; b3 = 0, 50, 800; b4 = 0, 400, 800; b5 = 50, 800; and b6 = 50, 400, 800 s/mm2 ...
May 2018: Korean Journal of Radiology: Official Journal of the Korean Radiological Society
Benedikt Rieger, Mehmet Akçakaya, José C Pariente, Sara Llufriu, Eloy Martinez-Heras, Sebastian Weingärtner, Lothar R Schad
Magnetic resonance fingerprinting (MRF) is a promising method for fast simultaneous quantification of multiple tissue parameters. The objective of this study is to improve the coverage of MRF based on echo-planar imaging (MRF-EPI) by using a slice-interleaved acquisition scheme. For this, the MRF-EPI is modified to acquire several slices in a randomized interleaved manner, increasing the effective repetition time of the spoiled gradient echo readout acquisition in each slice. Per-slice matching of the signal-trace to a precomputed dictionary allows the generation of T1 and T2 * maps with integrated B1 + correction...
April 27, 2018: Scientific Reports
Daichi Yamada, Hiroshi Ishimoto, Xiaodong Li, Tsunehiko Kohashi, Yuki Ishikawa, Azusa Kamikouchi
Many animals use acoustic signals to attract a potential mating partner. In fruit flies ( Drosophila melanogaster ), the courtship pulse song has a species-specific inter-pulse interval (IPI) that activates mating. Although a series of auditory neurons in the fly brain exhibit different tuning patterns to IPIs, it is unclear how the response of each neuron is tuned. Here we studied the neural circuitry regulating the activity of AMMC-B1 neurons, key secondary auditory neurons in the excitatory neural pathway that relay song information...
April 24, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Stefan H G Rietsch, Stephan Orzada, Stefan Maderwald, Sascha Brunheim, Bart W J Philips, Tom W J Scheenen, Mark E Ladd, Harald H Quick
PURPOSE: In this work a combined body coil array with 8 transmit/receive (Tx/Rx) meander elements and with 24 receive-only (Rx) loops (8Tx/32Rx) was developed and evaluated in comparison to an 8-channel transmit/receive body array (8Tx/Rx) based on meander elements serving as the reference standard. METHODS: Systematic evaluation of the RF array was performed on a body-sized phantom. Body imaging at 7T was performed in 6 volunteers in the body regions pelvis, abdomen, and heart...
April 21, 2018: Medical Physics
Richard D Dortch, Francesca Bagnato, Daniel F Gochberg, John C Gore, Seth A Smith
PURPOSE: To optimize a selective inversion recovery (SIR) sequence for macromolecular content mapping in the human brain at 3.0T. THEORY AND METHODS: SIR is a quantitative method for measuring magnetization transfer (qMT) that uses a low-power, on-resonance inversion pulse. This results in a biexponential recovery of free water signal that can be sampled at various inversion/predelay times (tI/ tD ) to estimate a subset of qMT parameters, including the macromolecular-to-free pool-size-ratio (PSR), the R1 of free water (R1f ), and the rate of MT exchange (kmf )...
March 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Julianna D Ianni, Zhipeng Cao, William A Grissom
PURPOSE: To obviate online slice-by-slice RF shim optimization and reduce B1+ mapping requirements for patient-specific RF shimming in high-field magnetic resonance imaging. THEORY AND METHODS: RF Shim Prediction by Iteratively Projected Ridge Regression (PIPRR) predicts patient-specific, SAR-efficient RF shims with a machine learning approach that merges learning with training shim design. To evaluate it, a set of B1+ maps was simulated for 100 human heads for a 24-element coil at 7T...
March 23, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Gang Chen, Bei Zhang, Martijn A Cloos, Daniel K Sodickson, Graham C Wiggins
PURPOSE: Transmit arrays are essential tools for various RF shimming or parallel excitation techniques at 7T. Here we present an array design with triangular coils to improve diversity in the B1 profiles in the longitudinal (z) direction and allow for next-nearest neighbor decoupling. METHODS: Two cylindrical 8-channel arrays having the same length and diameter, 1 of triangular coils and the other of rectangular coils, were constructed and compared in phantom imaging experiments using measures of excitation distribution for a variety of RF shim settings and geometry factor maps for different accelerations on different planes...
March 23, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Michael J van Rijssel, Josien P W Pluim, Peter R Luijten, Kenneth G A Gilhuijs, Alexander W J Raaijmakers, Dennis W J Klomp
Dynamic contrast-enhanced MRI is the workhorse of breast MRI, where the diagnosis of lesions is largely based on the enhancement curve shape. However, this curve shape is biased by RF transmit (B1 + ) field inhomogeneities. B1 + field information is required in order to correct these. The use of a generic, coil-specific B1 + template is proposed and tested. Finite-difference time-domain simulations for B1 + were performed for healthy female volunteers with a wide range of breast anatomies. A generic B1 + template was constructed by averaging simulations based on four volunteers...
March 23, 2018: NMR in Biomedicine
Seung-Chul Choi, Zhiwei Xu, Wei Li, Hong Yang, Derry C Roopenian, Herbert C Morse, Laurence Morel
Mouse models of lupus have shown that multiple immune cell types contribute to autoimmune disease. This study sought to investigate the involvement of B cells and dendritic cells in supporting the expansion of inflammatory and regulatory CD4+ T cells that are critical for lupus pathogenesis. We used lupus-prone B6.NZM2410.Sle1.Sle2.Sle3 (TC) and congenic C57BL/6J (B6) control mice to investigate how the genetic predisposition of these two cell types controls the activity of normal B6 T cells. Using an allogeneic in vitro assay, we showed that TC B1-a and conventional B cells expanded Th17 cells significantly more than their B6 counterparts...
March 21, 2018: Journal of Immunology: Official Journal of the American Association of Immunologists
Tobias Würschum, Guozheng Liu, Philipp H G Boeven, C Friedrich H Longin, Vilson Mirdita, Ebrahim Kazman, Yusheng Zhao, Jochen C Reif
The portfolio of available Reduced height loci (Rht-B1, Rht-D1, and Rht24) can be exploited for hybrid wheat breeding to achieve the desired heights in the female and male parents, as well as in the hybrids, without adverse effects on other traits relevant for hybrid seed production. Plant height is an important trait in wheat line breeding, but is of even greater importance in hybrid wheat breeding. Here, the height of the female and male parental lines must be controlled and adjusted relative to each other to maximize hybrid seed production...
March 19, 2018: TAG. Theoretical and Applied Genetics. Theoretische und Angewandte Genetik
Eleni Demetriou, Mohamed Tachrount, Moritz Zaiss, Karin Shmueli, Xavier Golay
PURPOSE: To develop a new MRI technique to rapidly measure exchange rates in CEST MRI. METHODS: A novel pulse sequence for measuring chemical exchange rates through a progressive saturation recovery process, called PRO-QUEST (progressive saturation for quantifying exchange rates using saturation times), has been developed. Using this method, the water magnetization is sampled under non-steady-state conditions, and off-resonance saturation is interleaved with the acquisition of images obtained through a Look-Locker type of acquisition...
March 5, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Tobias Würschum, Simon M Langer, C Friedrich H Longin, Matthew R Tucker, Willmar L Leiser
The broad adaptability of heading time has contributed to the global success of wheat in a diverse array of climatic conditions. Here, we investigated the genetic architecture underlying heading time in a large panel of 1,110 winter wheat cultivars of worldwide origin. Genome-wide association mapping, in combination with the analysis of major phenology loci, revealed a three-component system that facilitates the adaptation of heading time in winter wheat. The photoperiod sensitivity locus Ppd-D1 was found to account for almost half of the genotypic variance in this panel and can advance or delay heading by many days...
February 26, 2018: Plant, Cell & Environment
Fabian Kording, Bjoern P Schoennagel, Manuela Tavares de Sousa, Kai Fehrs, Gerhard Adam, Jin Yamamura, Christian Ruprecht
PURPOSE: Fetal cardiac MRI has the potential to play an important role in the assessment of fetal cardiac pathologies, but it is up to now not feasible due to a missing gating method. The purpose of this work was the evaluation of Doppler ultrasound (DUS) for external fetal cardiac gating with regard to compatibility, functionality, and reliability. Preliminary results were assessed performing fetal cardiac MRI. METHODS: An MRI conditional DUS device was developed to obtain a gating signal from the fetal heart...
February 21, 2018: Magnetic Resonance in Medical Sciences: MRMS
Niklaus Zoelch, Andreas Hock, Anke Henning
Quantification of magnetic resonance spectroscopy signals using the phantom replacement method requires an adequate correction of differences between the acquisition of the reference signal in the phantom and the measurement in vivo. Applying the principle of reciprocity, sensitivity differences can be corrected at low field strength by measuring the RF transmitter gain needed to obtain a certain flip angle in the measured volume. However, at higher field strength the transmit sensitivity may vary from the reception sensitivity, which leads to wrongly estimated concentrations...
May 2018: NMR in Biomedicine
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"