NMR in Biomedicine

Cover image for Vol. 26 Issue 11

November 2013

Volume 26, Issue 11

Pages i–ii, 1339–1607

  1. Issue information

    1. Top of page
    2. Issue information
    3. Research articles
    1. Issue Information (pages i–ii)

      Version of Record online: 18 OCT 2013 | DOI: 10.1002/nbm.2864

  2. Research articles

    1. Top of page
    2. Issue information
    3. Research articles
    1. DTI of human skeletal muscle: the effects of diffusion encoding parameters, signal-to-noise ratio and T2 on tensor indices and fiber tracts (pages 1339–1352)

      Martijn Froeling, Aart J. Nederveen, Klaas Nicolay and Gustav J. Strijkers

      Version of Record online: 14 MAY 2013 | DOI: 10.1002/nbm.2959

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      In this study, we have performed a number of simulations and MRI measurements to address the effects of diffusion encoding parameters, signal-to-noise ratio (SNR) and T2 on skeletal muscle tensor indices and fiber tracts. DTI of skeletal muscle requires an SNR of at least 25, a b value between 400 and 500 s/mm2 and data acquired with at least 12 diffusion gradient directions. When comparing studies or interpreting apparent changes in diffusion parameters, this should be performed with care, as differences between studies or changes as a result of pathology could have secondary causes.

    2. Unedited in vivo detection and quantification of γ-aminobutyric acid in the occipital cortex using short-TE MRS at 3 T (pages 1353–1362)

      Jamie Near, Jesper Andersson, Eduard Maron, Ralf Mekle, Rolf Gruetter, Philip Cowen and Peter Jezzard

      Version of Record online: 22 MAY 2013 | DOI: 10.1002/nbm.2960

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      In this study, short-TE MRS was investigated as a means of detecting γ-aminobutyric acid (GABA) in the occipital cortex at 3 T. The accuracy and reproducibility of short-TE MRS were assessed through both Monte Carlo simulations and in vivo experiments. Results indicate that the reproducibility of short-TE GABA measurements in the occipital cortex is comparable with that of gold-standard spectral editing approaches, but that the accuracy is strongly dependent on the experimental conditions.

    3. Quantification of human high-energy phosphate metabolite concentrations at 3 T with partial volume and sensitivity corrections (pages 1363–1371)

      AbdEl-Monem M. El-Sharkawy, Refaat E. Gabr, Michael Schär, Robert G. Weiss and Paul A. Bottomley

      Version of Record online: 3 JUN 2013 | DOI: 10.1002/nbm.2961

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      Practical acquisition and analysis protocols are presented to quantify [PCr] and [ATP] semi-automatically for the first timeat 3 T, with one-dimensionally resolved surface coil spectra and concentration referencing-. The method is validated in phantoms of different sizes and concentrations, and used to measure [PCr] and [ATP] in healthy subjects. In calf muscle (n = 8), [PCr] = 24.7 ± 3.4 and [ATP] = 5.7 ± 1.3 µmol/g wet weight, whereas, in heart (n = 18), [PCr] = 10.4 ± 1.5 and [ATP] = 6.0 ± 1.1 µmol/g wet weight (all mean ± SD), consistent with previous reports at lower fields.

    4. Texture-based and diffusion-weighted discrimination of parotid gland lesions on MR images at 3.0 Tesla (pages 1372–1379)

      Julia Fruehwald-Pallamar, Christian Czerny, Laura Holzer-Fruehwald, Stefan F. Nemec, Christina Mueller-Mang, Michael Weber and Marius E. Mayerhoefer

      Version of Record online: 23 MAY 2013 | DOI: 10.1002/nbm.2962

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      The purpose of our retrospective study was to evaluate whether texture-based analysis of standard MRI sequences and diffusion-weighted imaging can help in the discrimination of parotid gland masses. Texture analysis proved to differentiate benign from malignant lesions, as well as pleomorphic adenomas from Warthin tumors, based on standard T1-TSE sequences (without and with contrast). In all benign parotid masses, Warthin tumors had significantly lower ADC values than the other entities.

    5. Accelerating hyperpolarized metabolic imaging of the heart by exploiting spatiotemporal correlations (pages 1380–1386)

      Kilian Weiss, Andreas Sigfridsson, Lukas Wissmann, Julia Busch, Michael Batel, Marcin Krajewski, Matthias Ernst and Sebastian Kozerke

      Version of Record online: 25 APR 2013 | DOI: 10.1002/nbm.2963

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      In this work, spatial and temporal correlations present in dynamic series of images of hyperpolarized compounds in the heart were exploited to accelerate data acquisition. The k–t principal component analysis (PCA) method was implemented and tested using numerical simulations. Five-fold prospective undersampling was applied to hyperpolarized imaging of rat hearts in vivo, enabling 1 × 1-mm2 in-plane voxel size at a temporal resolution of 3 s.

    6. Measuring anisotropic muscle stiffness properties using elastography (pages 1387–1394)

      M. A. Green, G. Geng, E. Qin, R. Sinkus, S. C. Gandevia and L. E. Bilston

      Version of Record online: 3 MAY 2013 | DOI: 10.1002/nbm.2964

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      MR elastography was used in combination with diffusion tensor imaging to measure shear modulus anisotropy in the human skeletal muscle in the lower leg. The results showed significant differences in the medial gastrocnemius and the soleus muscles, where the shear modulus measured in the direction parallel to the muscle fibres was greater than that measured perpendicular to the muscle fibres.

    7. An embedded four-channel receive-only RF coil array for fMRI experiments of the somatosensory pathway in conscious awake marmosets (pages 1395–1402)

      Daniel Papoti, Cecil Chern-Chyi Yen, Julie B. Mackel, Hellmut Merkle and Afonso C. Silva

      Version of Record online: 22 MAY 2013 | DOI: 10.1002/nbm.2965

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      An embedded four-channel receive-only RF coil array was constructed and optimized for fMRI experiments of the somatosensory pathway in conscious, awake marmosets. The array was designed as part of a helmet-based head restraint system used to prevent motion during the MRI data acquisition. High SNR was obtained by building the array elements using a thin and flexible substrate glued to the inner surface of the restraint helmet, minimizing the distance between the array elements and the somatosensory cortex.

    8. Effects of exercise-induced intracellular acidosis on the phosphocreatine recovery kinetics: a 31P MRS study in three muscle groups in humans (pages 1403–1411)

      Gwenael Layec, Emil Malucelli, Y. Le Fur, David Manners, Kazuya Yashiro, Claudia Testa, Patrick J. Cozzone, Stefano Iotti and David Bendahan

      Version of Record online: 23 MAY 2013 | DOI: 10.1002/nbm.2966

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      The metabolic variability across muscles cannot be fully explained by differences in fiber type or the chronic load experienced by the quadriceps, finger and plantar flexor muscles, thereby pointing to intrinsic metabolic differences and supporting the concept of skeletal muscle heterogeneity. Finger flexor muscles also exhibit a greater sensitivity to the inhibitory effect of cytosolic acidosis on mitochondrial respiration, which could be related to a greater permeability of the mitochondrial membrane and, to some extent, to proton efflux rates.

    9. In vivo MRI analysis of depth-dependent ultrastructure in human knee cartilage at 7 T (pages 1412–1419)

      Nikita Garnov, Wilfried Gründer, Gregor Thörmer, Robert Trampel, Robert Turner, Thomas Kahn and Harald Busse

      Version of Record online: 25 JUN 2013 | DOI: 10.1002/nbm.2968

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      Ten younger (21–30) and ten older (55–76 years old) healthy volunteers were imaged with a T2-weighted spin-echo sequence in a 7 T whole-body MRI. Applying a “fascicle” model of the collagen-fiber arrangement, the boundary positions between radial and transitional zones were assessed from intensity profiles in small ROIs in the femur and tibia, and normalized to cartilage thickness. The radial zone in the femoral cartilage of younger volunteers has been found to be significantly thicker than that of older ones.

    10. Improved three-dimensional Look–Locker acquisition scheme and angle map filtering procedure for T1 estimation (pages 1420–1430)

      CheukKai Hui, Emilio Esparza-Coss and Ponnada A. Narayana

      Version of Record online: 20 JUN 2013 | DOI: 10.1002/nbm.2969

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      An elliptical k-space segmentation scheme is implemented to improve the three-dimensional Look–Locker T1 mapping data acquisition. In addition, a filtering procedure based on the goodness of fit (GOF) is developed to improve the consistency of the flip angle map estimates. These methods have been shown to improve the accuracy of T1 estimation.

      Application of the proposed methods shows reduced estimated errors compared with the use of traditional methods.

    11. A 22-channel receive array with Helmholtz transmit coil for anesthetized macaque MRI at 3 T (pages 1431–1440)

      Thomas Janssens, Boris Keil, Peter Serano, Azma Mareyam, Jennifer A. McNab, Lawrence L. Wald and Wim Vanduffel

      Version of Record online: 23 MAY 2013 | DOI: 10.1002/nbm.2970

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      A 22-channel receive coil array with a local Helmholtz transmit coil was constructed for rapid high-resolution anesthetized macaque monkey MRI at 3 T. Using this coil, the signal-to-noise ratio (SNR) in peripheral brain was 2.4 and 1.7 times greater than that obtained with single- and four-channel coils, respectively. The improved SNR was exploited to acquire high-resolution accelerated images with reduced required scan time for functional, anatomical and diffusion-weighted imaging.

    12. You have full text access to this OnlineOpen article
      Metabolic imaging of acute and chronic infarction in the perfused rat heart using hyperpolarised [1-13C]pyruvate (pages 1441–1450)

      Daniel R. Ball, Rachel Cruickshank, Carolyn A. Carr, Daniel J. Stuckey, Philip Lee, Kieran Clarke and Damian J. Tyler

      Version of Record online: 14 JUN 2013 | DOI: 10.1002/nbm.2972

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      Studies of metabolic alterations associated with myocardial infarction are frequently performed in isolated perfused rat hearts. In this work, we used hyperpolarized [1-13C]pyruvate to generate metabolic maps of the pyruvate-derived metabolites, lactate and bicarbonate, in the isolated perfused rat heart following both acute and chronic myocardial infarction. The images produced revealed alterations in myocardial perfusion, as well as significant alterations in metabolism, in both the acutely and chronically infarcted heart

    13. Ultrashort-TE MRI longitudinal study and characterization of a chronic model of asthma in mice: inflammation and bronchial remodeling assessment (pages 1451–1459)

      Andrea Bianchi, Annaïg Ozier, Olga Ousova, Gérard Raffard and Yannick Crémillieux

      Version of Record online: 13 JUN 2013 | DOI: 10.1002/nbm.2975

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      We present here an ultrashort-TE (UTE) 1H MRI high-resolution study of a chronic model of asthma in mice with the aim to longitudinally assess the main features of asthma using a fully noninvasive approach. This study shows, for the first time, that high-resolution UTE 1H MRI of the lungs may allow the noninvasive quantification of peribronchial eosinophilic inflammation with airways occlusion by mucus and of bronchial remodeling in a murine asthma model that correlates with functional parameters.

    14. A comprehensive non-invasive framework for automated evaluation of acute renal transplant rejection using DCE-MRI (pages 1460–1470)

      Fahmi Khalifa, Mohamed Abou El-Ghar, Behnaz Abdollahi, Hermann B. Frieboes, Tarek El-Diasty and Ayman El-Baz

      Version of Record online: 18 JUN 2013 | DOI: 10.1002/nbm.2977

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      We propose a new framework for non-invasive identification of acute renal transplant rejection using DCE-MRI. Our framework performs sequentially deformable model segmentation of the kidney, non-rigid registration of time series data for local motion correction, cortex segmentation and construction of the agent kinetic curves, function-based modeling of the perfusion curves using the gamma-variate function, and feature extraction and classification of kidney status. Both the 95% confidence interval statistic and ROC analysis document the ability to separate rejection and non-rejection groups in a cohort of 50 patients.

    15. Multiple-echo diffusion tensor acquisition technique (MEDITATE) on a 3T clinical scanner (pages 1471–1483)

      Steven H. Baete, Gene Cho and Eric E. Sigmund

      Version of Record online: 5 JUL 2013 | DOI: 10.1002/nbm.2978

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      In the MEDITATE sequence, a set of RF pulses generates multiple echoes, the amplitudes of which are diffusion weighted in both magnitude and direction by a pattern of diffusion gradients. As a result, two scans with different diffusion weighting strengths suffice to estimate DTI parameters accurately. In these first in vivo results, MEDITATE was expanded to reduce T2 weighting and implemented on a 3T full-body Siemens scanner; good quantitative agreement was found with standard TRSE DTI results in (an)isotropic phantoms and in vivo muscle tissue.

    16. The impact of myelination on axon sparing and locomotor function recovery in spinal cord injury assessed using diffusion tensor imaging (pages 1484–1495)

      Tsang-Wei Tu, Joong H. Kim, Feng Qin Yin, Lyn B. Jakeman and Sheng-Kwei Song

      Version of Record online: 18 JUN 2013 | DOI: 10.1002/nbm.2981

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      The current study uses in vivo diffusion tensor imaging (DTI) and end-point histology to investigate the role of myelin integrity in axonal sparing and locomotor function after contusion spinal cord injury in dysmyelinated shiverer mice and in their heterozygous littermates. The data suggest that the DTI markers reflect the structural changes in white matter tracts, and correlate with the recovery of neurological function. This study confirms that the myelin sheath is critical for a higher hind limb function in uninjured mice. However, when the locomotor function is limited by the damage to long fiber tracts at the chronic phase after mid-thoracic spinal cord injury, recovery is independent of the presence of residual myelin or the degree of radial diffusivity; instead, the degree of spared axons is critical, and is reflected by measures of axial diffusivity in DTI.

    17. Enhancing the [13C]bicarbonate signal in cardiac hyperpolarized [1-13C]pyruvate MRS studies by infusion of glucose, insulin and potassium (pages 1496–1500)

      Mette Hauge Lauritzen, Christoffer Laustsen, Sadia Asghar Butt, Peter Magnusson, Lise Vejby Søgaard, Jan Henrik Ardenkjær-Larsen and Per Åkeson

      Version of Record online: 24 JUN 2013 | DOI: 10.1002/nbm.2982

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      In cardiac hyperpolarized [1-13C]pyruvate MRS studies, the infusion of glucose, insulin and potassium (GIK) at two different doses was used to increase the myocardial glucose oxidation through the citric acid cycle in fasted rats. A significant increase in the [13C]bicarbonate signal was observed in the high-dose group, representing an increased flux of pyruvate through the pyruvate dehydrogenase enzyme complex. A high [13C]bicarbonate signal is attractive in cardiac hyperpolarized 13C MRS studies as changes in the [13C]bicarbonate signal can provide important information on different cardiac disease states.

    18. Characterization of choline kinase in human endothelial cells (pages 1501–1507)

      Noriko Mori, Mayur Gadiya, Flonné Wildes, Balaji Krishnamachary, Kristine Glunde and Zaver M. Bhujwalla

      Version of Record online: 18 JUN 2013 | DOI: 10.1002/nbm.2983

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      Here, we have determined the expression of choline kinase-α (Chk-α) in human vascular endothelial cells, and the effect of Chk-α downregulation on endothelial cell proliferation. Endothelial cells showed low Chk-α relative to MDA-MB-231 human breast cancer cells, and downregulation of Chk-α mRNA to comparable levels in both cell lines did not affect endothelial cell proliferation, in contrast with the significant decrease in proliferation observed in breast cancer cells. Characterization of the endothelial cell marker CD31 by immunostaining in tumors from mice injected with a lentiviral vector that transduces cells with Chk-short hairpin RNA (shRNA) or with control luciferase (Luc)-shRNA did not reveal a significant difference in CD31 density, further confirming that Chk-α is a cancer-specific target.

    19. High-resolution imaging of magnetisation transfer and nuclear Overhauser effect in the human visual cortex at 7 T (pages 1508–1517)

      Olivier Mougin, Matthew Clemence, Andrew Peters, Alain Pitiot and Penny Gowland

      Version of Record online: 26 JUN 2013 | DOI: 10.1002/nbm.2984

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      A magnetisation transfer (MT) sequence was designed to study the variation in MT and nuclear Overhauser enhancement (NOE) across the cortex, and showed changes consistent with the variation in myelination across the cortex. In regions in which the stria of Gennari was visible on T2*-weighted images, it could also be detected in signals sensitive to MT, and there was greater variation in signals sensitive to NOE, suggesting that the NOE signal is more sensitive to myelination.

    20. Variability in fasting lipid and glycogen contents in hepatic and skeletal muscle tissue in subjects with and without type 2 diabetes: a 1H and 13C MRS study (pages 1518–1526)

      M. C. Stephenson, E. Leverton, E. Y. H. Khoo, S. M. Poucher, L. Johansson, J. A. Lockton, J. W. Eriksson, P. Mansell, P. G. Morris and I. A. MacDonald

      Version of Record online: 9 JUL 2013 | DOI: 10.1002/nbm.2985

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      In this study, we assessed the variability in repeat measurements of hepatic and skeletal muscle lipid and glycogen over 1 month and compared these with the reproducibility of measurements made in a single session. The variability in MRS measurements of liver glycogen and lipid content over 1 month was greater than the reproducibility seen within a single session, indicating significant biological variation. These observations will have important implications in the planning of studies investigating the pathophysiology of type 2 diabetes mellitus and potential therapies.

    21. Timing dependence of peripheral pulse-wave-triggered pulsed arterial spin labeling (pages 1527–1533)

      Yasutaka Fushimi, Tomohisa Okada, Akira Yamamoto, Mitsunori Kanagaki, Koji Fujimoto and Kaori Togashi

      Version of Record online: 20 JUN 2013 | DOI: 10.1002/nbm.2986

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      Peripheral pulse-wave-triggered arterial spin labeling (PPWT-ASL) strongly affects cerebral blood flow (CBF) values compared with nontriggered (NT)-ASL in anterior cerebral artery (ACA) and middle cerebral artery (MCA) territories, especially when measured at the foot of the carotid artery flow phase. CBF_NT was assumed to lie approximately between the minimum and maximum CBFs with clear statistical significance in several regions of interest at several time points of PPWT-ASL, and CBF_NT was assumed to resemble ‘randomly triggered’ PPWT-ASL. PPWT-ASL strongly affects CBF values compared with NT-ASL, particularly at the foot of carotid artery flow in ACA and MCA territories.

    22. MR elastography in a murine stroke model reveals correlation of macroscopic viscoelastic properties of the brain with neuronal density (pages 1534–1539)

      Florian Baptist Freimann, Susanne Müller, Kaspar-Josche Streitberger, Jing Guo, Sergej Rot, Adnan Ghori, Peter Vajkoczy, Rolf Reiter, Ingolf Sack and Jürgen Braun

      Version of Record online: 20 JUN 2013 | DOI: 10.1002/nbm.2987

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      The structure of cerebral tissue was altered by transient middle cerebral artery occlusion in a mouse model. MR elastography was used to measure viscoelastic tissue parameters in vivo. A significant correlation between the shear modulus of brain tissue and the number of neurons was observed, which proved to be stronger in the ischemic hemisphere relative to the unaffected contralateral hemisphere of the brain.

    23. Using microbubbles as an MRI contrast agent for the measurement of cerebral blood volume (pages 1540–1546)

      Shin-Lei Peng, Fu-Nien Wang, Chung-Hsin Wang, Hsu-Hsia Peng, Chih-Tien Lu and Chih-Kuang Yeh

      Version of Record online: 24 JUN 2013 | DOI: 10.1002/nbm.2988

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      Microbubbles (MBs) were used as an MR susceptibility contrast agent as a result of the susceptibility differences at the gas–liquid interface. In this study, we investigated the relationship between the relative cerebral blood volume (rCBV) derived from gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) (rCBVGd) and the MB-induced susceptibility effect from MBs (ΔR2*MB), and found the key factor influencing the correlation. The results show that, as the time to peak (TTP) of the MB trial increases, the correlation between rCBVGd and ΔR2*MB increases.

    24. Resonant inductive decoupling (RID) for transceiver arrays to compensate for both reactive and resistive components of the mutual impedance (pages 1547–1554)

      Nikolai I. Avdievich, Jullie W. Pan and Hoby P. Hetherington

      Version of Record online: 18 JUN 2013 | DOI: 10.1002/nbm.2989

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      Transceiver surface coil arrays improve transmit performance and B1 homogeneity for high-field head imaging. Decoupling is the most challenging aspect in the design of transceiver arrays. Previously described decoupling techniques have focused on the elimination of the mutual inductance only, which limits the obtainable decoupling as a result of residual mutual resistance. A novel resonant inductive decoupling (RID), which allows compensation for both mutual reactance and resistance between the adjacent antennas, has been developed and verified experimentally.

    25. High-permittivity solid ceramic resonators for high-field human MRI (pages 1555–1561)

      S. A. Aussenhofer and A. G. Webb

      Version of Record online: 4 JUL 2013 | DOI: 10.1002/nbm.2990

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      An annular dielectric resonator made from a high-permittivity low-loss ceramic has been designed to operate in degenerate quadrature HEM11 modes at 298.1 MHz (7 T). High-resolution in vivo images have been obtained from human digits. Possibilities for novel double-tuned resonator configurations are also discussed.

    26. Quantitative MRI and ultrastructural examination of the cuprizone mouse model of demyelination (pages 1562–1581)

      Jonathan D. Thiessen, Yanbo Zhang, Handi Zhang, Lingyan Wang, Richard Buist, Marc R. Del Bigio, Jiming Kong, Xin-Min Li and Melanie Martin

      Version of Record online: 13 AUG 2013 | DOI: 10.1002/nbm.2992

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      Cellular features in electron micrographs of the corpus callosum were correlated to several different quantitative MRI metrics. The largest Spearman correlation coefficient varied depending on cellular type: T1 versus the myelinated axon fraction (ρ = −0.90), the bound pool fraction (ƒ) versus the myelin sheath fraction (ρ = 0.93), and axial diffusivity versus the non-myelinated cell fraction (ρ = 0.92). ƒ was the strongest indicator of myelin content while longitudinal relaxation rates and diffusivity measurements were the strongest indicators of changes in tissue structure.

    27. Automated transfer and injection of hyperpolarized molecules with polarization measurement prior to in vivo NMR (pages 1582–1588)

      Tian Cheng, Mor Mishkovsky, Jessica A. M. Bastiaansen, Olivier Ouari, Patrick Hautle, Paul Tordo, Ben van den Brandt and Arnaud Comment

      Version of Record online: 25 JUL 2013 | DOI: 10.1002/nbm.2993

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      We present an automated method to perform in vivo hyperpolarized 13C NMR experiments based on dissolution dynamic nuclear polarization. The method includes (a) a precise determination of the infusate 13C polarization inside the imager prior to injection, (b) a radical scavenging process that does not reduce the final infusate concentration and (c) a minimum delay of 3 s between preparation and injection of the hyperpolarized solutions into live animals.

    28. In vivo three-dimensional molecular imaging with Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) at high spatiotemporal resolution (pages 1589–1595)

      Daniel Coman, Robin A. de Graaf, Douglas L. Rothman and Fahmeed Hyder

      Version of Record online: 24 JUL 2013 | DOI: 10.1002/nbm.2995

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      Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) from complexes between paramagnetic lanthanide (III) ions (e.g Tm3+) and macrocyclic chelates (e.g 1,4,7,10-tetraacetate, DOTMA4–) allows rapid chemical shift imaging (CSI) data acquisition. The CSI signal is significantly enhanced by employing reduced spherical encoding with Gaussian weighting (RESEGAW) of k space. In vitro and in vivo three-dimensional CSI data with an effective volume of 1.0 μL acquired within 5 min using TmDOTMAsuggest that acqusition employing RESEGAW can be used for molecular mapping with BIRDS.

    29. In vivo GABA T2 determination with J-refocused echo time extension at 7 T (pages 1596–1601)

      A. Andreychenko, D. W. J. Klomp, R. A. de Graaf, P. R. Luijten and V. O. Boer

      Version of Record online: 26 JUL 2013 | DOI: 10.1002/nbm.2997

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      In order to measure the T2 relaxation time, the signal intensity has to be obtained at multiple echo times. For a coupled spin system such as GABA this is challenging, since J-couplings influence the signal shapes and amplitudes depending on which echo time is used. To refocus J-modulation, a chemical shift selective refocusing pulse can be used. This method was applied in combination with the MEGA-sLASER editing technique to measure the in vivo T2 relaxation time of GABA (87 ± 11 ms) at 7 T.

    30. High-resolution MRI encoding using radiofrequency phase gradients (pages 1602–1607)

      Jonathan C. Sharp, Scott B. King, Qunli Deng, Vyacheslav Volotovskyy and Boguslaw Tomanek

      Version of Record online: 6 SEP 2013 | DOI: 10.1002/nbm.3023

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      We present an MRI principle which operates entirely without the use of conventional field gradients. This new approach uses only the resonant radiofrequency (RF) field to produce Fourier spatial encoding equivalent to conventional MRI. High-resolution two-dimensional-encoded in vivo MR images have been obtained. This approach exploits RF field phase gradients and offers the possibility of very low-cost diagnostics and novel experiments exploiting unique capabilities, such as imaging without disturbance of the main magnetic field.