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Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine

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https://www.readbyqxmd.com/read/30106186/looping-star
#1
Florian Wiesinger, Anne Menini, Ana Beatriz Solana
PURPOSE: To introduce a novel MR pulse sequence, termed Looping Star, for fast, robust, and yet quiet, 3D radial multi-gradient echo T2* MR imaging. METHODS: The Looping Star pulse sequence is based on the 3D radial Rotating Ultra-Fast Imaging Sequence (RUFIS) extended by a time-multiplexed gradient-refocusing mechanism. First, multiple magnetic coherences are excited, which are subsequently gradient-refocused in form of a looping k-space trajectory. Accordingly, Looping Star captures an initial FID image followed by gradient echo images at equidistant echo times...
August 14, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30094874/prediction-of-peripheral-nerve-stimulation-thresholds-of-mri-gradient-coils-using-coupled-electromagnetic-and-neurodynamic-simulations
#2
Mathias Davids, Bastien Guérin, Axel Vom Endt, Lothar R Schad, Lawrence L Wald
PURPOSE: As gradient performance increases, peripheral nerve stimulation (PNS) is becoming a significant constraint for fast MRI. Despite its impact, PNS is not directly included in the coil design process. Instead, the PNS characteristics of a gradient are assessed on healthy subjects after prototype construction. We attempt to develop a tool to inform coil design by predicting the PNS thresholds and activation locations in the human body using electromagnetic field simulations coupled to a neurodynamic model...
August 9, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30084505/accelerating-compressed-sensing-in-parallel-imaging-reconstructions-using-an-efficient-circulant-preconditioner-for-cartesian-trajectories
#3
Kirsten Koolstra, Jeroen van Gemert, Peter Börnert, Andrew Webb, Rob Remis
PURPOSE: Design of a preconditioner for fast and efficient parallel imaging (PI) and compressed sensing (CS) reconstructions for Cartesian trajectories. THEORY: PI and CS reconstructions become time consuming when the problem size or the number of coils is large, due to the large linear system of equations that has to be solved in ℓ1 and ℓ2-norm based reconstruction algorithms. Such linear systems can be solved efficiently using effective preconditioning techniques...
August 7, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058296/evaluating-the-accuracy-of-multicomponent-t-2-parameters-for-luminal-water-imaging-of-the-prostate-with-acceleration-using-inner-volume-3d-grase
#4
Rachel W Chan, Angus Z Lau, Garry Detzler, Vivekanandan Thayalasuthan, Robert K Nam, Masoom A Haider
PURPOSE: Prostate cancer can be detected using a multicomponent T2 mapping technique termed luminal water imaging. The purpose of this study is twofold: 1) To accelerate the luminal water imaging acquisition by using inner volume selection as part of a gradient and spin echo sequence, and 2) to evaluate the accuracy of luminal water fractions and multicomponent T2 relaxation times. METHODS: The accuracy of parameter estimates was assessed using Monte Carlo simulations, in phantom experiments and in the prostate (in 5 healthy subjects)...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058252/five-minute-whole-heart-coronary-mra-with-sub-millimeter-isotropic-resolution-100-respiratory-scan-efficiency-and-3d-prost-reconstruction
#5
Aurélien Bustin, Giulia Ginami, Gastão Cruz, Teresa Correia, Tevfik F Ismail, Imran Rashid, Radhouene Neji, René M Botnar, Claudia Prieto
PURPOSE: To enable whole-heart 3D coronary magnetic resonance angiography (CMRA) with isotropic sub-millimeter resolution in a clinically feasible scan time by combining respiratory motion correction with highly accelerated variable density sampling in concert with a novel 3D patch-based undersampled reconstruction (3D-PROST). METHODS: An undersampled variable density spiral-like Cartesian trajectory was combined with 2D image-based navigators to achieve 100% respiratory efficiency and predictable scan time...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058240/glucocest-imaging-with-on-resonance-variable-delay-multiple-pulse-onvdmp-mri
#6
Xiang Xu, Jiadi Xu, Kannie W Y Chan, Jing Liu, Huanling Liu, Yuguo Li, Lin Chen, Guanshu Liu, Peter C M van Zijl
PURPOSE: To examine the detection sensitivity for the rapidly exchanging hydroxyl protons of D-glucose using the recently developed on-resonance variable delay multi-pulse (onVDMP) chemical exchange saturation transfer (CEST) technique. METHODS: The onVDMP method was applied for the detection of water signal changes upon venous D-glucose infusion in mice with 9L glioma xenografts. The effect size of onVDMP MRI during infusion was compared with that of conventional continuous wave (CW) CEST MRI...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058224/effect-of-k-space-weighted-image-contrast-and-ultrasound-focus-size-on-the-accuracy-of-proton-resonance-frequency-thermometry
#7
Bryant T Svedin, Christopher R Dillon, Dennis L Parker
PURPOSE: To construct a predictive model that describes how the duration and symmetry of a k-space-weighted image contrast (KWIC) window affects the temporal resolution of differently sized ultrasound foci when using a pseudo-golden angle stack-of-stars acquisition. METHODS: We performed a modulation analysis of proton resonance frequency temperature measurements to create the temporal modulation transfer function for KWIC windows of different symmetry and temporal duration...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058220/comparison-of-prospective-head-motion-correction-with-nmr-field-probes-and-an-optical-tracking-system
#8
Martin Eschelbach, Ali Aghaeifar, Jonas Bause, Jonas Handwerker, Jens Anders, Eva-Maria Engel, Axel Thielscher, Klaus Scheffler
PURPOSE: The aim of this study was to compare prospective head motion correction and motion tracking abilities of two tracking systems: Active NMR field probes and a Moiré phase tracking camera system using an optical marker. METHODS: Both tracking systems were used simultaneously on human subjects. The prospective head motion correction was compared in an MP2RAGE and a gradient echo sequence. In addition, the motion tracking trajectories for three subjects were compared against each other and their correlation and deviations were analyzed...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058216/head-motion-measurement-and-correction-using-fid-navigators
#9
Tess E Wallace, Onur Afacan, Maryna Waszak, Tobias Kober, Simon K Warfield
PURPOSE: To develop a novel framework for rapid, intrinsic head motion measurement in MRI using FID navigators (FIDnavs) from a multichannel head coil array. METHODS: FIDnavs encode substantial rigid-body motion information; however, current implementations require patient-specific training with external tracking data to extract quantitative positional changes. In this work, a forward model of FIDnav signals was calibrated using simulated movement of a reference image within a model of the spatial coil sensitivities...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058204/optimizing-maternal-fat-suppression-with-constrained-image-based-shimming-in-fetal-mr
#10
Andreia S Gaspar, Rita G Nunes, Giulio Ferrazzi, Emer J Hughes, Jana Hutter, Shaihan J Malik, Laura McCabe, Kelly P Baruteau, Mary A Rutherford, Joseph V Hajnal, Anthony N Price
PURPOSE: Echo planar imaging (EPI) is the primary sequence for functional and diffusion MRI. In fetal applications, the large field of view needed to encode the maternal abdomen leads to prolonged EPI readouts, which may be further extended due to safety considerations that limit gradient performance. The resulting images become very sensitive to water-fat shift and susceptibility artefacts. The purpose of this study was to reduce artefacts and increase stability of EPI in fetal brain imaging, balancing local field homogeneity across the fetal brain with longer range variations to ensure compatibility with fat suppression of the maternal abdomen...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058202/relaxometry-and-quantification-in-simultaneously-acquired-single-and-triple-quantum-filtered-sodium-mri
#11
Wieland A Worthoff, Aliaksandra Shymanskaya, N Jon Shah
PURPOSE: Sodium imaging delivers valuable information about in vivo metabolism and pathophysiology. Image quantification can benefit the diagnosis and characterization of existing pathologies and the clinical course of a disease. An enhanced SISTINA sequence is proposed for sodium imaging and for the estimation of sodium tissue parameters for a 2-compartment model of the brain, such as relaxation times in intracellular space and tissue, intracellular volume fraction, and intracellular molar fraction...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058197/gradient-controlled-local-larmor-adjustment-gc-lola-for-simultaneous-multislice-bssfp-imaging-with-improved-banding-behavior
#12
Daniel Stäb, Peter Speier
PURPOSE: Simultaneous multislice (SMS) accelerated balanced SSFP (bSSFP) imaging can be impaired by off-resonance effects, due to slice-specific alterations in the frequency response. In this work, we introduce gradient-controlled local Larmor adjustment as a means to restore the frequency response and to stabilize SMS-accelerated bSSFP imaging with respect to banding artifacts. METHODS: Providing each simultaneously excited slice with an individual RF phase cycle in SMS-accelerated bSSFP imaging results in the sequence's frequency response being shifted slice-specifically along the off-resonance axis...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058186/adaptive-sar-mass-averaging-framework-to-improve-predictions-of-local-rf-heating-near-a-hip-implant-for-parallel-transmit-at-7-t
#13
Aurelien Destruel, Kieran O'Brien, Jin Jin, Feng Liu, Markus Barth, Stuart Crozier
PURPOSE: Magnetic resonance imaging is used increasingly to scan patients with hip prostheses. We evaluated the reliability of 10 g-averaged specific absorption rate (SAR10g ) to predict radiofrequency (RF) heating in tissues surrounding a hip implant at 7 T in an 8-channel pTx hip coil. A new adaptive SAR mass-averaging method is proposed to improve the correlation between the distribution of mass-averaged SAR and that of tissue temperature. METHODS: Currently, RF safety standards for implants are based on temperature instead of SAR, as SAR has not been introduced with regard to exposure scenarios with implants...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058173/multi-echo-gre-based-conductivity-imaging-using-kalman-phase-estimation-method
#14
Kanghyun Ryu, Jaewook Shin, Hongpyo Lee, Jun-Hyeong Kim, Dong-Hyun Kim
PURPOSE: To obtain in vivo electrical conductivity images from multi-echo gradient-echo (mGRE) sequence using a zero-TE phase extrapolation algorithm based on the Kalman method. METHODS: For estimation of the zero-TE phase from the mGRE data, an iterative algorithm consisting of a combination of the Kalman filter, Kalman smoother, and expectation maximization was implemented and compared with linear extrapolation methods. Simulations were performed for verification, and phantom and in vivo studies were conducted for validation...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058167/motion-compensation-using-principal-component-analysis-and-projection-onto-dipole-fields-for-abdominal-magnetic-resonance-thermometry
#15
Jeremy Tan, Charles Mougenot, Samuel Pichardo, James M Drake, Adam C Waspe
PURPOSE: High intensity focused ultrasound (HIFU) has the potential to locally and non-invasively treat cancer with fewer side effects than alternative therapies. However, motion and tissue heterogeneity in the abdomen can compromise the HIFU focus and confound current thermometry methods. METHODS: The proposed thermometry method combines principal component analysis (PCA), as a multi-baseline technique, and projection onto dipole fields (PDF), as a near-referenceless method...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058162/black-blood-myocardial-t-2-mapping
#16
Chengyan Wang, Jihye Jang, Ulf Neisius, Maryam Nezafat, Ahmed Fahmy, Jinkyu Kang, Jennifer Rodriguez, Beth Goddu, Patrick Pierce, Sophie Berg, Jue Zhang, Xiaoying Wang, Reza Nezafat
PURPOSE: To develop a black blood heart-rate adaptive T2 -prepared balanced steady-state free-precession (BEATS) sequence for myocardial T2 mapping. METHODS: In BEATS, blood suppression is achieved by using a combination of preexcitation and double inversion recovery pulses. The timing and flip angles of the preexcitation pulse are auto-calculated in each patient based on heart rate. Numerical simulations, phantom studies, and in vivo studies were conducted to evaluate the performance of BEATS...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058148/determination-of-multipool-contributions-to-endogenous-amide-proton-transfer-effects-in-global-ischemia-with-high-spectral-resolution-in-vivo-chemical-exchange-saturation-transfer-mri
#17
Iris Yuwen Zhou, Dongshuang Lu, Yang Ji, Limin Wu, Enfeng Wang, Jerry S Cheung, Xiao-An Zhang, Phillip Zhe Sun
PURPOSE: Chemical exchange saturation transfer (CEST) MRI has been used for quantitative assessment of dilute metabolites and/or pH in disorders such as acute stroke and tumor. However, routine asymmetry analysis (MTRasym ) may be confounded by concomitant effects such as semisolid macromolecular magnetization transfer (MT) and nuclear Overhauser enhancement. Resolving multiple contributions is essential for elucidating the origins of in vivo CEST contrast. METHODS: Here we used a newly proposed image downsampling expedited adaptive least-squares fitting on densely sampled Z-spectrum to quantify multipool contribution from water, nuclear Overhauser enhancement, MT, guanidinium, amine, and amide protons in adult male Wistar rats before and after global ischemia...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058147/dynamic-off-resonance-correction-for-spiral-real-time-mri-of-speech
#18
Yongwan Lim, Sajan Goud Lingala, Shrikanth S Narayanan, Krishna S Nayak
PURPOSE: To improve the depiction and tracking of vocal tract articulators in spiral real-time MRI (RT-MRI) of speech production by estimating and correcting for dynamic changes in off-resonance. METHODS: The proposed method computes a dynamic field map from the phase of single-TE dynamic images after a coil phase compensation where complex coil sensitivity maps are estimated from the single-TE dynamic scan itself. This method is tested using simulations and in vivo data...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058128/toward-more-reliable-measurements-of-noe-effects-in-cest-spectra-at-around-1-6-ppm-noe-1-6-in-rat-brain
#19
Zhongliang Zu
PURPOSE: Recently, a new relayed nuclear Overhauser enhancement (NOE) saturation transfer effect at around -1.6 parts per million, termed NOE(-1.6), and its potential applications in tumor and stroke were reported by several institutes. However, there is a concern of the reproducibility of NOE(-1.6) measurements because it is not reported by many other publications. This paper aims to study the influence of typically overlooked experimental settings on the NOE(-1.6) signal and to build a framework for more reliable measurements of NOE(-1...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30058123/sources-of-hepatic-glycogen-synthesis-in-mice-fed-with-glucose-or-fructose-as-the-sole-dietary-carbohydrate
#20
Ivana Jarak, Cristina Barosa, Fatima O Martins, Joao C P Silva, Cristiano Santos, Getachew Debas Belew, Joao Rito, Ivan Viegas, Jose Teixeira, Paulo J Oliveira, John G Jones
PURPOSE: The positional analysis of hepatic glycogen enrichment from deuterated water (2 H2 O) by 2 H NMR has been applied previously to resolve the contributions of glucose and fructose to glycogen synthesis in rodents fed a high sucrose diet. To further validate this method, this analysis was applied to mice fed with synthetic diets whose carbohydrate components consisted solely of either glucose or fructose. METHODS: Eight glucose-fed and 12 fructose-fed mice were given 2 H2 O followed by ad libitum feeding overnight...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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