NMR in Biomedicine

Cover image for Vol. 29 Issue 8

Early View (Online Version of Record published before inclusion in an issue)

Impact Factor: 2.983

ISI Journal Citation Reports © Ranking: 2015: 10/43 (Spectroscopy); 26/72 (Biophysics); 26/124 (Radiology Nuclear Medicine & Medical Imaging)

Online ISSN: 1099-1492

Associated Title(s): Contrast Media & Molecular Imaging

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  1. 1 - 45
  1. Research articles

    1. Towards longitudinal mapping of extracellular pH in gliomas

      Yuegao Huang, Daniel Coman, Peter Herman, Jyotsna U. Rao, Samuel Maritim and Fahmeed Hyder

      Version of Record online: 29 JUL 2016 | DOI: 10.1002/nbm.3578

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      Imaging extracellular pH (pHe) with biosensor imaging of redundant deviation in shifts (BIRDS) meets an important cancer research need. However, the method requires surgical intervention to raise BIRDS probe concentration. To temporarily restrict renal clearance and allow BIRDS without surgical intervention we developed a probenecid/TmDOTP5− co-infusion method. The pHe was unaffected by the probe dose in rats bearing RG2, 9 L, and U87 brain tumors. The method enables repeated scans with BIRDS in the same subject for tumor assessment and treatment

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  2. Special issue research articles

    1. Chemical exchange saturation transfer of the cervical spinal cord at 7 T

      Adrienne N. Dula, Siddharama Pawate, Lindsey M. Dethrage, Benjamin N. Conrad, Blake E. Dewey, Robert L. Barry and Seth A. Smith

      Version of Record online: 26 JUL 2016 | DOI: 10.1002/nbm.3581

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      Optimal chemical exchange saturation transfer (CEST) saturation parameters found via simulation were implemented for CEST MRI in 10 healthy controls and 10 patients with multiple sclerosis (MS), and results were examined using traditional asymmetry analysis and the Lorentzian fitting method. Distinct spectral features for all tissue types studied were found both up- and downfield from the water resonance. The z spectra in healthy subjects had the expected z spectral shape with CEST effects apparent from 2.0 to 4.5 ppm, whereas the z spectra from patients with MS demonstrated deviations from this expected normal shape, indicating this method's sensitivity to known pathology, as well as tissues appearing normal on conventional MRI.

  3. Research articles

    1. A rapid inversion technique for the measurement of longitudinal relaxation times of brain metabolites: application to lactate in high-grade gliomas at 3 T

      Karl Landheer, Arjun Sahgal, Sten Myrehaug, Albert P. Chen, Charles H. Cunningham and Simon J. Graham

      Version of Record online: 25 JUL 2016 | DOI: 10.1002/nbm.3580

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      A rapid inversion technique was combined with a lactate-editing sequence to measure the lipid-free longitudinal relaxation time of lactate, estimated to be 2000 ± 280 ms. Numerically optimized inversion times were used to maximize the precision for a set scan duration. The mean absolute concentration of lactate corrected for T1 and T2 was estimated as 4.3 ± 2.6 mm.

    2. Pulsed and oscillating gradient MRI for assessment of cell size and extracellular space (POMACE) in mouse gliomas

      Olivier Reynaud, Kerryanne Veronica Winters, Dung Minh Hoang, Youssef Zaim Wadghiri, Dmitry S. Novikov and Sungheon Gene Kim

      Version of Record online: 22 JUL 2016 | DOI: 10.1002/nbm.3577

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      Using a geometrical model of impermeable spheres, the time dependence of the diffusion coefficient measured by combining oscillating and pulsed gradient spin echo diffusion MRI under the POMACE framework is used to derive in vivo and ex vivo parametric maps of extracellular space (ECS) volume fraction, cell size and intra- and extracellular diffusivities in mouse GBM. Results are compared with conventional DWI metrics, electron microscopy, alternative ECS measurements based on effective medium theory, and optical microscopy performed on the same samples.

  4. Special issue review articles

    1. Overview of quantitative susceptibility mapping

      Andreas Deistung, Ferdinand Schweser and Jürgen R. Reichenbach

      Version of Record online: 19 JUL 2016 | DOI: 10.1002/nbm.3569

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      In this article, we review the theoretical basics of quantitative susceptibility mapping (QSM) and susceptibility tensor imaging and briefly summarize the computational strategies for the characterization of magnetic susceptibility with MRI phase. In addition, we provide an overview of current methodological and clinical applications of QSM with a focus on brain imaging.

  5. Special issue research articles

    1. Single-step quantitative susceptibility mapping with variational penalties

      Itthi Chatnuntawech, Patrick McDaniel, Stephen F. Cauley, Borjan A. Gagoski, Christian Langkammer, Adrian Martin, P. Ellen Grant, Lawrence L. Wald, Kawin Setsompop, Elfar Adalsteinsson and Berkin Bilgic

      Version of Record online: 22 JUN 2016 | DOI: 10.1002/nbm.3570

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      The tissue susceptibility distribution is directly estimated from the raw phase of a gradient echo acquisition by solving total variation (TV) and total generalized variation (TGV) regularized optimization problems. Efficient algorithms for the proposed single-step quantitative susceptibility mapping (QSM) reconstructions, which permit analytical solutions to all the subproblems, are developed based on the alternating direction method of multipliers (ADMM). A dramatic reduction in dipole streaking artifacts and improved homogeneity of image contrast over conventional QSM are demonstrated using numerical simulations and in vivo experiments that were acquired using signal-to-noise ratio (SNR)-efficient acquisitions including multi-echo Wave-CAIPI (controlled aliasing in parallel imaging) and three-dimensional echo planar imaging (3D EPI).

    2. A comprehensive numerical analysis of background phase correction with V-SHARP

      Pinar Senay Özbay, Andreas Deistung, Xiang Feng, Daniel Nanz, Jürgen Rainer Reichenbach and Ferdinand Schweser

      Version of Record online: 3 JUN 2016 | DOI: 10.1002/nbm.3550

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      We propose a new V-SHARP scheme, with optimal and generalized parameters, based on a high-pass filtering approach. The local root-mean-square error (RMSE) between the results from V-SHARP and the ground-truth, background-corrected field map decreased as the center of the brain was approached. The optimal susceptibility maps were calculated for a radius between 6 and 10 mm and a regularization parameter between 0 and 0.01 mm−1. With the novel scheme, the regularization parameter is independent of other imaging parameters, such as the image resolution.

  6. Special issue review articles

    1. Skeletal muscle diffusion tensor-MRI fiber tracking: rationale, data acquisition and analysis methods, applications and future directions

      Bruce M. Damon, Martijn Froeling, Amanda K. W. Buck, Jos Oudeman, Zhaohua Ding, Aart J. Nederveen, Emily C. Bush and Gustav J. Strijkers

      Version of Record online: 3 JUN 2016 | DOI: 10.1002/nbm.3563

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      A muscle's abilities to generate force and actuate movement are influenced, in part, by the arrangement of fibers with respect to the muscle's mechanical line of action. We describe the use of diffusion tensor-MRI (DT-MRI) muscle fiber tracking for the study of this structure. We discuss the importance of muscle structure to muscle function, describe DT-MRI's application to muscle, discuss issues related to data acquisition and analysis, show how DT-MRI has provided new insights into muscle function and highlight future research directions.

    2. Contributions to magnetic susceptibility of brain tissue

      Jeff H. Duyn and John Schenck

      Version of Record online: 30 MAY 2016 | DOI: 10.1002/nbm.3546

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      In human brain, iron and myelin are major contributors to MRI magnetic susceptibility contrast. Both their concentration, as well as their microscropic distribution, determine the strength of their contribution. Inferring concentrations from susceptibility weighted MRI requires conjoint analysis of both amplitude and phase of the signal decay curve, and simplifying assumptions about the contrast mechanism.

    3. Computational methods for image reconstruction

      Julianne Chung and Lars Ruthotto

      Version of Record online: 26 MAY 2016 | DOI: 10.1002/nbm.3545

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      We review analytical tools and state-of-the-art computational tools for solving image reconstruction problems. By comparing quantitative susceptibility mapping (QSM) with the classic image-deblurring problem, we show that a severe challenge for QSM reconstruction is to distinguish between noise and signal contributions in the data; therefore regularization methods are crucial. We survey some regularization approaches and regularization parameter selection methods and discuss efficient numerical implementations for large-scale QSM problems.

  7. Special issue research articles

    1. Determination of detection sensitivity for cerebral microbleeds using susceptibility-weighted imaging

      Sagar Buch, Yu-Chung N. Cheng, Jiani Hu, Saifeng Liu, John Beaver, Rajasimhan Rajagovindan and E. Mark Haacke

      Version of Record online: 20 MAY 2016 | DOI: 10.1002/nbm.3551

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      A direct formulaic approach is proposed that uses spherical simulations to estimate the underlying size of a cerebral microbleed (CMB) based on the number of radiologically detected voxels, the estimated susceptibility and acquisition parameters. A comparison between measured values and values derived from our formulae for the prediction of the number of voxels detected due to the blooming effect for CMBs with diameters of 2 voxels (a, b) and 1 voxel (c, d). Signal-to-noise ratio (SNR) values are 47 : 1 for 7-T, 20 : 1 for 3-T and 10 : 1 for 1.5-T simulations, is shown in the Figure.

  8. Special issue review articles

    1. Susceptibility-weighted imaging: current status and future directions

      Saifeng Liu, Sagar Buch, Yongsheng Chen, Hyun-Seok Choi, Yongming Dai, Charbel Habib, Jiani Hu, Joon-Yong Jung, Yu Luo, David Utriainen, Meiyun Wang, Dongmei Wu, Shuang Xia and E. Mark Haacke

      Version of Record online: 18 MAY 2016 | DOI: 10.1002/nbm.3552

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      Susceptibility-weighted imaging (SWI) is a method that uses the intrinsic nature of local magnetic fields to enhance image contrast in order to improve the visibility of various susceptibility sources and to facilitate diagnostic interpretation. In this article, we review the basics of SWI, with discussions on data acquisition, reconstruction and post-processing. In addition, we show a few clinical applications of SWI, such as the imaging of stroke, traumatic brain injury, the carotid vessel wall and siderotic nodules in cirrhotic liver.

  9. Special issue research articles

    1. 1H MRS in the human spinal cord at 7 T using a dielectric waveguide transmitter, RF shimming and a high density receive array

      A. Henning, W. Koning, A. Fuchs, A. Raaijmakers, J. J. Bluemink, C. A. T. van den Berg, V. O. Boer and D. W. J. Klomp

      Version of Record online: 18 MAY 2016 | DOI: 10.1002/nbm.3541

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      This paper reports the first 7 T spinal cord 1H MR spectra. To tackle the B1+ inhomogeneity during transmission at 7 T a dielectric waveguide and dipole antenna transmission coil, dual channel RF shimming and inner-volume saturated sLASER were combined. A tight fit 30-channel receive array enabled optimal SNR. Quantitative results from seven independent scans were obtained and compared with previous 3 T results.

    2. Dentate nucleus iron deposition is a potential biomarker for tremor-dominant Parkinson's disease

      Naying He, Pei Huang, Huawei Ling, Jason Langley, Chunlei Liu, Bei Ding, Juan Huang, Hongmin Xu, Yong Zhang, Zhongping Zhang, Xiaoping Hu, Shengdi Chen and Fuhua Yan

      Version of Record online: 18 MAY 2016 | DOI: 10.1002/nbm.3554

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      The tremor-dominant (TD) Parkinson's disease group showed increased susceptibility in the bilateral dentate nucleus (DN) compared with the healthy control group. No difference was seen in R2* between the TD group and healthy control group, indicating that the deposited iron in DN may comprise smaller iron particles. The DN susceptibility in drug-naive PD patients was positively correlated with tremor score. These findings indicate that iron load within DN may make an important contribution to motor phenotypes in PD.

  10. Special issue review articles

    1. Magnetic susceptibility anisotropy outside the central nervous system

      Russell Dibb, Luke Xie, Hongjiang Wei and Chunlei Liu

      Version of Record online: 16 MAY 2016 | DOI: 10.1002/nbm.3544

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      Magnetic susceptibility anisotropy is observed in tissues throughout the body and arises from a variety of organized molecular sources including the epithelial lipids in the kidney, myofilament proteins in the heart, and collagen fibrils in connective tissue. Two MRI tools, susceptibility tensor imaging and quantitative susceptibility mapping, have exploited this anisotropy to assess the microstructure and orientation of renal tubules, myofibers, and articular cartilage. Measuring susceptibility anisotropy using MRI is a promising technique for studying healthy and diseased organ tissues.

  11. Special issue research articles

    1. MR phase imaging with bipolar acquisition

      Joseph Dagher and Kambiz Nael

      Version of Record online: 5 MAY 2016 | DOI: 10.1002/nbm.3523

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      Bipolar (non-yback) multi-echo readouts offer significant SNR advantages over monopolar echo readouts, but introduce unknown phase errors. We present a novel MR phase-imaging method that jointly disambiguates errors from bipolar readouts as well as errors from phase wrapping, phase noise and channel-dependent phase offsets. The approach, based on voxel-per-voxel maximum-likelihood estimation, enables MR phase imaging in SNR-limited scenarios, such as at in-plane resolutions of 310 µm at 3 T.

  12. Special issue review articles

    1. Iron quantification with susceptibility

      Stefan Ropele and Christian Langkammer

      Version of Record online: 27 APR 2016 | DOI: 10.1002/nbm.3534

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      Iron in tissue can cause local and non-local changes of the magnetic field, which strongly depend on the spin state and valence of its electrons in the iron compound. Quantitative susceptibility mapping allows to assess the iron content and typically shows a good linear relationship with iron concentration. Larger uncertainties may arise in myelinated fibers and in the presence of mineralized iron with unknown magnetic phases such as hemosiderin or hemozoin.

    2. Susceptibility tensor imaging (STI) of the brain

      Wei Li, Chunlei Liu, Timothy Q. Duong, Peter C. M. van Zijl and Xu Li

      Version of Record online: 27 APR 2016 | DOI: 10.1002/nbm.3540

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      Susceptibility tensor imaging (STI) is a recently developed MRI technique that allows quantitative determination of orientation-independent magnetic susceptibility parameters from gradient echo signal phase. By modeling the magnetic susceptibility of each voxel as a symmetric rank-2 tensor, individual magnetic susceptibility tensor elements as well as the magnetic susceptibility anisotropy (MSA) can be determined for brain tissues. Similar to diffusion tensor imaging (DTI), STI allows mapping of brain white matter fiber orientations and reconstruction of 3D white matter pathways using the principal eigenvectors of the susceptibility tensor.

  13. Special issue research articles

    1. Investigating lipids as a source of chemical exchange-induced MRI frequency shifts

      K. Shmueli, S. J. Dodd, P. van Gelderen and J. H. Duyn

      Version of Record online: 13 APR 2016 | DOI: 10.1002/nbm.3525

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      We measured exchange-induced frequency shifts (fe) in a model of cell membranes consisting of multilamellar vesicles of cerebrosides and phospholipids. Using chemical shift imaging, with dioxane as an internal reference to remove susceptibility-induced frequency shifts, we found significant increases in fe with increasing lipid concentration: 0.044 ± 0.008 ppb/mM (r2 = 0.877, p < 0.01). We also measured and corrected for the water–dioxane frequency shift which was –0.021 ± 0.002 ppb/mM dioxane in agreement with previous measurements at low dioxane concentrations.

  14. Special issue review articles

    1. Mechanisms of T2* anisotropy and gradient echo myelin water imaging

      Jongho Lee, Yoonho Nam, Joon Yul Choi, Eung Yeop Kim, Se-Hong Oh and Dong-Hyun Kim

      Version of Record online: 7 APR 2016 | DOI: 10.1002/nbm.3513

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      A white matter voxel demonstrates T2* anisotropy that originates from isotropic and anisotropic magnetic susceptibility and multi-compartmental microstructure induced frequency shifts. These mechanisms result in multi-exponential magnitude decay and nonlinear phase evolution. Using the complex signal, myelin water fraction can be estimated, producing gradient echo myelin water imaging.

    2. Susceptibility-based time-resolved whole-organ and regional tissue oximetry

      Felix W. Wehrli, Audrey P. Fan, Zachary B. Rodgers, Erin K. Englund and Michael C. Langham

      Version of Record online: 26 FEB 2016 | DOI: 10.1002/nbm.3495

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      Quantification of reactive hyperemia with dynamic oximetry showing cross-sectional phase difference image of the thigh, 10 cm below the inferior boundary of the pressure cuff along with post-ischemia femoral vein SvO2 time course, and series of zoomed phase images showing relative phase of venous blood during period indicated. Darker blue represents lower saturation levels. Parameterization of time-course data yields quantitative metrics: washout time, upslope and overshoot.

  15. Special issue research articles

    1. Reproducibility of R2* and quantitative susceptibility mapping (QSM) reconstruction methods in the basal ganglia of healthy subjects

      M. D. Santin, M. Didier, R. Valabrègue, L. Yahia Cherif, D. García-Lorenzo, P. Loureiro de Sousa, E. Bardinet and S. Lehéricy

      Version of Record online: 23 FEB 2016 | DOI: 10.1002/nbm.3491

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      The registration of four sessions of three-dimensional gradient echo complex images in a cohort of healthy subjects allowed the quantification of the reproducibility of quantitative susceptibility mapping (QSM) methods versus the reproducibility of more conventional R2* mapping. The sensitivity to changes in the QSM technique was shown to reach a level of 1.5% in the basal ganglia.

    2. Joint 2D and 3D phase processing for quantitative susceptibility mapping: application to 2D echo-planar imaging

      Hongjiang Wei, Yuyao Zhang, Eric Gibbs, Nan-Kuei Chen, Nian Wang and Chunlei Liu

      Version of Record online: 17 FEB 2016 | DOI: 10.1002/nbm.3501

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      Current two-dimensional (2D) echo-planar imaging (EPI)-based quantitative susceptibility mapping (QSM) uses three-dimensional (3D) phase unwrapping followed by 3D background phase removal, and leaves phase inconsistencies across slices. Here, we report a new data processing procedure that integrates 2D and 3D phase processing to reduce phase inconsistencies between slices. Experimental results show that the new 2D EPI-based QSM method can produce quantitative susceptibility measures that are comparable with those of time-consuming 3D gradient-echo (GRE)-based QSM.

    3. Quantitative susceptibility mapping at 3 T: comparison of acquisition methodologies

      M. Louis Lauzon, Cheryl R. McCreary, D. Adam McLean, Marina Salluzzi and Richard Frayne

      Version of Record online: 17 FEB 2016 | DOI: 10.1002/nbm.3492

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      We compared deep grey matter susceptibility (χ) values in healthy adults acquired from various quantitative susceptibility mapping (QSM) sequences at 3 T using unipolar or bipolar readout gradients, accelerated imaging or not (R2 or R1), with/without gradient-warp correction (GW). Using a linear mixed effects model, only GW was found to alter the χ estimate, but its overall effect was small (~5%).

  16. Special issue review articles

    1. New insights into rotating frame relaxation at high field

      John T. Spear and John C. Gore

      Version of Record online: 11 FEB 2016 | DOI: 10.1002/nbm.3490

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      Spin-locking at high static fields provides the ability to examine relatively slow molecular motions, specifically diffusion and chemical exchange, which are shown to dominate relaxation in the rotating frame. R dispersions provide insight into these relaxation mechanisms, and these are shown to be independent effects through finite difference simulations and experiments examining the impact of blood oxygenation. These mechanisms can be exploited further to potentially estimate solute concentrations in mixtures or to infer geometric distributions of inhomogeneities.

  17. Special issue research articles

    1. Regionally progressive accumulation of iron in Parkinson's disease as measured by quantitative susceptibility mapping

      Xiaojun Guan, Min Xuan, Quanquan Gu, Peiyu Huang, Chunlei Liu, Nian Wang, Xiaojun Xu, Wei Luo and Minming Zhang

      Version of Record online: 8 FEB 2016 | DOI: 10.1002/nbm.3489

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      Quantitative susceptibility mapping was used to confirm a regionally progressive pattern of iron accumulation in patients with Parkinson's disease (PD) at different stages, which indicates that iron deposition in the substantia nigra pars compacta (SNc) is affected exclusively in the early PD (EPD) patients, while the substantia nigra pars reticulata (SNr), red nucleus (RN) and globus pallidus internal (GPi) as well as globus pallidus external (GPe) become involved in the late PD (LPD) patients.

  18. Special issue review articles

    1. Rapid brain MRI acquisition techniques at ultra-high fields

      Kawin Setsompop, David A. Feinberg and Jonathan R. Polimeni

      Version of Record online: 2 FEB 2016 | DOI: 10.1002/nbm.3478

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      Recent development trends in moving away from 2D imaging to simultaneous multislice (SMS) and 3D imaging have provided dramatic improvements in acquisition speed and SNR efficiency for high-resolution imaging at ultra-high field. SMS and 3D imaging can make better use of coil sensitivity information for parallel imaging acquisitions through controlled aliasing in multiple spatial directions. This has enabled unprecedented acceleration factors of an order of magnitude or higher, with low artifact levels and high SNR.

    2. In vivo diffusion MRS investigation of non-water molecules in biological tissues

      Peng Cao and Ed X. Wu

      Version of Record online: 21 JAN 2016 | DOI: 10.1002/nbm.3481

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      In this review, recent diffusion MRS studies of biologically relevant non-water molecules under normal and diseased conditions will be presented. Technique considerations for diffusion MRS experiments will be discussed. With advances in MRI hardware and diffusion methodology, diffusion MRS of non-water molecules is expected to provide increasingly valuable and biologically specific information on tissue microstructures and physiology, complementing the traditional diffusion MR of small and ubiquitous water molecules.

    3. Diffusion MRI in early cancer therapeutic response assessment

      C. J. Galbán, B. A. Hoff, T. L. Chenevert and B. D. Ross

      Version of Record online: 15 JAN 2016 | DOI: 10.1002/nbm.3458

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      Diffusion-weighted MRI (DW-MRI) is sensitive to cellular changes and has been evaluated extensively as a quantitative and early imaging biomarker of the therapeutic response. DW-MR can be applied to many different solid tumors to detect changes in cellularity as measured by an early increase in the apparent diffusion coefficient (ADC) of water molecules within the lesion. An overview of DW-MRI acquisition protocols, quantitative image analysis approaches and applications implementing DW-MRI for the early prediction of cancer treatment response is presented.

    4. Diffusion lung imaging with hyperpolarized gas MRI

      Dmitriy A. Yablonskiy, Alexander L. Sukstanskii and James D. Quirk

      Version of Record online: 16 DEC 2015 | DOI: 10.1002/nbm.3448

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      Diffusion MRI with hyperpolarized gases provides quantitative information on lung microstructure at the alveolar level and makes it possible to measure the same morphometric parameters (mean linear intercept, surface-to-volume ratio, number of alveoli per unit volume) as have been traditionally obtained by means of invasive stereology.

  19. Special issue research articles

    1. Proton observed phosphorus editing (POPE) for in vivo detection of phospholipid metabolites

      Jannie P. Wijnen, Dennis W. J. Klomp, Christine I. H. C. Nabuurs, Robin A. de Graaf, Irene M. L. van Kalleveen, Wybe J. M. van der Kemp, Peter R. Luijten, Mark C. Kruit, Andrew Webb, Hermien E. Kan and Vincent O. Boer

      Version of Record online: 25 NOV 2015 | DOI: 10.1002/nbm.3440

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      We demonstrate the enhanced sensitivity of proton observed phosphorus editing (POPE) over direct 31P MRS with Ernst angle excitation for 1H–31P coupled metabolites in the human brain at 7 T.

  20. Special issue review articles

    1. Diffusion tensor imaging in abdominal organs

      Rotem Shlomo Lanzman and Hans-Jörg Wittsack

      Version of Record online: 11 NOV 2015 | DOI: 10.1002/nbm.3434

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      Diffusion tensor imaging of abdominal organs adds additional diagnostic information about the microstructure of human tissues. Besides the technical requirements for DTI in abdominal organs, recent studies of major organs such as kidney, liver, prostate and pelvic floor are presented and discussed.

    2. You have full text access to this OnlineOpen article
      Diffusion MRI in the heart

      Choukri Mekkaoui, Timothy G. Reese, Marcel P. Jackowski, Himanshu Bhat and David E. Sosnovik

      Version of Record online: 20 OCT 2015 | DOI: 10.1002/nbm.3426

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      Diffusion MRI provides unique information on the integrity of the myocardium without the need for exogenous contrast agents. However, diffusion MRI in the heart has proven technically challenging. In this review, we describe approaches that have been developed to overcome these challenges, and briefly examine the application of diffusion MRI in ischemic heart disease. The use of diffusion MRI as a clinical tool may lead to new and complementary approaches to diagnose and treat patients with heart disease.

  21. Special issue research articles

    1. Dipole antennas for ultrahigh-field body imaging: a comparison with loop coils

      A. J. E. Raaijmakers, P. R. Luijten and C. A. T. van den Berg

      Version of Record online: 17 AUG 2015 | DOI: 10.1002/nbm.3356

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      This article provides electromagnetic insight into the operating principles of dipole antennas by numerical simulations. It focuses on a comparison study of dipole antennas and loop coils at the frequencies of 128, 298 and 400 MHz. When the optimal element is chosen for each depth, loop coils have higher B1+ efficiency for shallow depths, whereas dipole antennas have higher B1+ efficiency for large depths. Loop coils demonstrate a better B1+/√SARmax ratio, but not in an array setup with overlapping elements.

    2. Concurrent recording of RF pulses and gradient fields – comprehensive field monitoring for MRI

      David O. Brunner, Benjamin E. Dietrich, Mustafa Çavuşoğlu, Bertram J. Wilm, Thomas Schmid, Simon Gross, Christoph Barmet and Klaas P. Pruessmann

      Version of Record online: 13 AUG 2015 | DOI: 10.1002/nbm.3359

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      By using NMR field probes in conjunction with broadband RF receivers, a stand-alone monitoring unit measuring RF pulses and gradient waveforms concurrently and with common timing was built. The unit can capture the field dynamics of multi-channel RF transmission systems without the need for dedicated RF pickups, and delivers a comprehensive sequence depiction as it is executed by the scanner. These abilities are exemplified by monitoring typically challenging applications such bSSFP, UTE and spatially selective parallel transmission pulses at 7 T.

  22. Special issue review articles

    1. Diffusion imaging of the vertebral bone marrow

      Olaf Dietrich, Tobias Geith, Maximilian F. Reiser and Andrea Baur-Melnyk

      Version of Record online: 26 JUN 2015 | DOI: 10.1002/nbm.3333

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      Diffusion-weighted MRI (DWI) of the vertebral bone marrow is a clinically important tool for the characterization of bone-marrow pathologies and, in particular, for the differentiation of benign and malignant vertebral compression fractures. DWI of the vertebral bone marrow is, however, complicated by some unique MR and tissue properties of vertebral bone marrow. This review summarizes data from numerous studies in which diffusion measurements of normal vertebral bone marrow and of different vertebral bone-marrow lesions were performed.

  23. Review articles

    1. You have full text access to this OnlineOpen article
      Parallel transmission for ultrahigh-field imaging

      Francesco Padormo, Arian Beqiri, Joseph V. Hajnal and Shaihan J. Malik

      Version of Record online: 19 MAY 2015 | DOI: 10.1002/nbm.3313

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      Ultrahigh-field MRI provides a powerful new investigational device for in vivo imaging, but is hindered by non-uniform and variable radiofrequency fields. Parallel transmission (PTx) promises to address these issues by providing more control over the fields. In this article, we review methods for exploiting the new degrees of freedom provided by PTx to improve image quality and to reduce the specific absorption rate (SAR).

  24. Special issue review articles

    1. The technological future of 7 T MRI hardware

      A. G. Webb and P. F. Van de Moortele

      Version of Record online: 14 MAY 2015 | DOI: 10.1002/nbm.3315

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      In this article we present some projections for future hardware developments on human 7 T MRI scanners. Areas covered include magnet design, magnetic field gradients, RF coils, dynamic shimming, SAR estimation, and patient monitoring.

  25. Special issue research articles

    1. A simple approach to evaluate the kinetic rate constant for ATP synthesis in resting human skeletal muscle at 7 T

      Jimin Ren, A. Dean Sherry and Craig R. Malloy

      Version of Record online: 6 MAY 2015 | DOI: 10.1002/nbm.3310

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      Extracting the ATP synthesis rate constant (kPi[RIGHTWARDS ARROW]γATP) from 31P inversion transfer measurements is generally complicated by the tangle of multiple spin relaxation and exchange parameters in the magnetization equations describing the exchange system. This problem can be avoided by using a simple alternative approach based on the Bloch–McConnell equation for inorganic phosphate Pi, which allows the evaluation of kPi[RIGHTWARDS ARROW]γATP by a linear plot of Pi magnetization rate (m˙Pi) against the magnetization difference between Pi and γ-ATP (mPi − mγATP) .

    2. You have full text access to this OnlineOpen article
      Assessment of blood flow velocity and pulsatility in cerebral perforating arteries with 7-T quantitative flow MRI

      W. H. Bouvy, L. J. Geurts, H. J. Kuijf, P. R. Luijten, L. J. Kappelle, G. J. Biessels and J. J. M. Zwanenburg

      Version of Record online: 27 APR 2015 | DOI: 10.1002/nbm.3306

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      A two-dimensional, single-slice, quantitative flow (Qflow) sequence on a 7-T system yielded the first non-invasive in vivo measurements of blood flow velocity and pulsatility in cerebral perforating arteries in the basal ganglia (BG) and semioval centre (CSO), with the middle cerebral artery as reference. The precision of the velocity measurements in individual vessels and the pulsatility index per anatomical region was determined using Bland–Altman analysis. This sequence allows the study of the haemodynamics of cerebral perforating arteries and their association with, for example, vascular lesions.

    3. Safety testing and operational procedures for self-developed radiofrequency coils

      Jens Hoffmann, Anke Henning, Ioannis A. Giapitzakis, Klaus Scheffler, G. Shajan, Rolf Pohmann and Nikolai I. Avdievich

      Version of Record online: 6 APR 2015 | DOI: 10.1002/nbm.3290

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      Herein, a comprehensive guideline on electrical and mechanical safety tests, specific absorption rate (SAR) simulation, risk analysis and operational procedures for self-developed RF coils is described that helps to recognize and eliminate safety concerns during RF coil design and operation. Although the procedure is generally applicable to all field strengths, specific requirements with regard to SAR simulation and verification, as well as electrical safety and performance, at ultrahigh-field are considered.

  26. Special issue review articles

    1. Recent applications of UHF-MRI in the study of human brain function and structure: a review

      Wietske van der Zwaag, Andreas Schäfer, José P. Marques, Robert Turner and Robert Trampel

      Version of Record online: 12 MAR 2015 | DOI: 10.1002/nbm.3275

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      MRI at ultra-high field strength of 7 T and greater has made tremendous progress over the last decade and a half. This review discusses the rapidly expanding literature on UHF applications of BOLD fMRI and structural imaging in the brain, including relaxation-time-weighted imaging, phase imaging, and QSM; angiography and diffusion- and MT-weighted imaging.

    2. Clinical applications at ultrahigh field (7  T). Where does it make the difference?

      Siegfried Trattnig, Wolfgang Bogner, Stephan Gruber, Pavol Szomolanyi, Vladimir Juras, Simon Robinson, Štefan Zbýň and Stefan Haneder

      Version of Record online: 12 MAR 2015 | DOI: 10.1002/nbm.3272

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      Although it will probably take some years before full whole-body investigations can be performed routinely with high quality at 7 T, many morphological applications, as well as metabolic and functional MRI applications, in neuroimaging, musculoskeletal and breast imaging have already been shown to be superior compared with the benchmark 3 T, which will further enhance the move to 7 T. The rapid increase in operating 7-T systems indicates the growing interest in ultrahigh-field MRI because of the improved clinical results with regard to morphological detail, as well as functional and metabolic imaging capabilities.

    3. W(h)ither human cardiac and body magnetic resonance at ultrahigh fields? technical advances, practical considerations, applications, and clinical opportunities

      Thoralf Niendorf, Katharina Paul, Celal Oezerdem, Andreas Graessl, Sabrina Klix, Till Huelnhagen, Fabian Hezel, Jan Rieger, Helmar Waiczies, Jens Frahm, Armin M. Nagel, Eva Oberacker and Lukas Winter

      Version of Record online: 23 FEB 2015 | DOI: 10.1002/nbm.3268

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      This work documents and reviews advances and progress in cardiac and body MR technology at ultrahigh fields and its application in forefront research and in early clinical applications. The achievements of ultrahigh field cardiac and body MR are shown to be a powerful motivator and enabler, since the extra speed, signal and imaging capabilities may be invested to overcome the fundamental constraints that continue to hamper traditional cardiac and body MR applications at lower magnetic field strengths.

  27. Special issue research articles

    1. Cortical phase changes measured using 7-T MRI in subjects with subjective cognitive impairment, and their association with cognitive function

      Sanneke van Rooden, Mathijs Buijs, Marjolein E. van Vliet, Maarten J. Versluis, Andrew G. Webb, Ania M. Oleksik, Lotte van de Wiel, Huub A. M. Middelkoop, Gerard Jan Blauw, Annelies W. E. Weverling-Rynsburger, Jeroen D. C. Goos, Wiesje M. van der Flier, Ted Koene, Philip Scheltens, Frederik Barkhof, Ondine van de Rest, P. Eline Slagboom, Mark A. van Buchem and Jeroen van der Grond

      Version of Record online: 19 DEC 2014 | DOI: 10.1002/nbm.3248

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      In subjects with subjective cognitive impairment (SCI), Alzheimer's disease-like changes may occur in the brain. We investigated whether cortical phase shifts at 7 T in SCI can be detected, implicating the deposition of amyloid-beta (Aβ) plaques and associated iron, and which cognitive domains are associated with cortical phase shifts in SCI. In SCI, an increased cortical phase shift at high field is associated with a poorer memory performance, although no increased phase shift could be determined in subjects with SCI compared with controls.

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