bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radial GRASE: Implementation and applications
Authors: Gmitro Arthur F. , Kono Mitsuko , Theilmann Rebecca J. , Altbach Maria I. , Li Zhiqiang , Trouard Theodore P. 
Published: May 2005

AbstractRAD‐GRASE is an MRI sequence that combines radial (RAD) k‐space scanning with the gradient and spin‐echo (GRASE) technique. RAD‐GRASE has the advantages of all radial data acquisition methods in that it can reduce motion sensitivity and correct motion‐induced data errors, which can be exploited to achieve high‐resolution diffusion‐weighted imaging (DWI). One can obtain different types of image contrast, including DWI, T1, T2, and T2*, in RAD‐GRASE by controlling the magnetization preparation and sequence timing. Moreover, because there is oversampling of the low spatial frequencies inherent to radial sequences, partial data reconstruction can be used to achieve multiple forms of image contrast from a single acquired data set, and to generate parametric image maps of equilibrium magnetization, T2, and T. The RAD‐GRASE technique can also be used to achieve fat‐suppressed and/or separated fat and water images by choosing the appropriate timing parameters. Magn Reson Med 53:1363–1371, 2005. © 2005 Wiley‐Liss, Inc.
Determination of mouse skeletal muscle architecture using three‐dimensional diffusion tensor imaging
Authors: Heemskerk Anneriet M. , Strijkers Gustav J. , Vilanova Anna , Drost Maarten R. , Nicolay Klaas 
Published: May 2005

AbstractMuscle architecture is the main determinant of the mechanical behavior of skeletal muscles. This study explored the feasibility of diffusion tensor imaging (DTI) and fiber tracking to noninvasively determine the in vivo three‐dimensional (3D) architecture of skeletal muscle in mouse hind leg. In six mice, the hindlimb was imaged with a diffusion‐weighted (DW) 3D fast spin‐echo (FSE) sequence followed by the acquisition of an exercise‐induced, T2‐enhanced data set. The data showed the expected fiber organization, from which the physiological cross‐sectional area (PCSA), fiber length, and pennation angle for the tibialis anterior (TA) were obtained. The values of these parameters ranged from 5.4–9.1 mm2, 5.8–7.8 mm, and 21–24°, respectively, which is in agreement with values obtained previously with the use of invasive methods. This study shows that 3D DT acquisition and fiber tracking is feasible for the skeletal muscle of mice, and thus enables the quantitative determination of muscle architecture. Magn Reson Med 53:1333–1340, 2005. © 2005 Wiley‐Liss, Inc.
The effect of B1 field inhomogeneity and the nonselective inversion profile on the kinetics of FAIR‐based perfusion MRI
Authors: Schepers Janneke , van Osch Matthias J. P. , Bartels Lambertus W. , Heukels Sean N. , Viergever Max A. , Nicolay Klaas 
Published: May 2005

AbstractPerfusion imaging with pulsed arterial spin labeling techniques, like flow‐sensitive alternating inversion recovery (FAIR), may suffer from inflow of fresh, i.e., unlabeled, spins. Inflow of fresh spins is caused by the arrival of unlabeled spins in the image slice and can lead to underestimation of the perfusion if not taken into account. In this study it was shown that a decrease in B1 field strength toward the edge of the transmit coil and the consequent reduction in the inversion efficiency leads to a narrowing of the arterial delivery function and a reduction in FAIR signal. Increasing the B1 amplitude of the adiabatic inversion pulse from 2.3 to 5.7 times its minimum amplitude requirement resulted in an observed increase of 40 to 80% in the rat brain FAIR signal at inflow times longer than 0.65 s. For coils with limited dimensions and significant B1 inhomogeneity over the perfusion labeling slab, the application of an excessively large B1 amplitude in combination with adiabatic inversion is recommended to optimize the FAIR perfusion contrast. Magn Reson Med 53:1355–1362, 2005. © 2005 Wiley‐Liss, Inc.
Multiexponential T2‐relaxation analysis in cerebrally damaged rats in the absence and presence of a gadolinium contrast agent
Authors: Lascialfari A. , Zucca I. , Asdente M. , Cimino M. , Guerrini U. , Paoletti R. , Tremoli E. , Lorusso V. , Sironi L. 
Published: May 2005

AbstractAn analysis of the multiexponential relaxation of transverse nuclear magnetization with and without a gadolinium‐based paramagnetic contrast agent in spontaneously hypertensive stroke‐prone rats (SHR‐SP) and in the rat model of ischemia induced by middle cerebral artery occlusion is described. From the multiexponential relaxation, the presence of two T2 relaxation times in the range of 0.03–0.5 s, T2A (shortest) and T2B (longest), with very different relative weights (respectively, A and B), is evidenced. In our models of cerebral damage, the changes in A and B were more evident than those in T2A and T2B. The two T2 values were interpreted as belonging to water molecules in two different compartments; therefore, the difference between the damaged and normal regions revealed by means of standard T2‐weighted images is suggested to be due to a different water distribution in the two compartments, rather than different T2's. The T2 relaxation in the SHR‐SP stroke model is analyzed for the first time using a multiexponential method. The power of a detailed analysis of MRI relaxation times is confirmed by the correspondence between the revealed changes in T2A, T2B, A and B, and the known T2W and DWI results about blood–brain barrier functionality. Magn Reson Med 53:1326–1332, 2005. © 2005 Wiley‐Liss, Inc.
3D MDEFT imaging of the human brain at 4.7 T with reduced sensitivity to radiofrequency inhomogeneity
Authors: Thomas David L. , De Vita Enrico , Deichmann Ralf , Turner Robert , Ordidge Roger J. 
Published: May 2005

AbstractA modification to the 3D modified driven equilibrium Fourier transform (MDEFT) imaging technique is proposed that reduces its sensitivity to RF inhomogeneity. This is especially important at high field strengths where RF focusing effects exacerbate B1 inhomogeneity, causing significant signal nonuniformity in the images. The adiabatic inversion pulse used during the preparation period of the MDEFT sequence is replaced by a hard (nonadiabatic) pulse with a nominal flip angle of 130°. The spatial inhomogeneity of the hard pulse preparation compensates for the inhomogeneity of the excitation pulses. Uniform signal intensity is obtained for a wide range of B1 amplitudes and the high CNR characteristic of MDEFT is retained. The new approach was validated by numerical simulations and successfully applied to human brain imaging at 4.7 T, resulting in high‐quality T1‐weighted images of the whole human brain at high field strength with uniform signal intensity and contrast, despite the presence of significant RF inhomogeneity. Magn Reson Med 53:1452–1458, 2005. © 2005 Wiley‐Liss, Inc.
Optimizing spatiotemporal sampling for k‐t BLAST and k‐t SENSE: Application to high‐resolution real‐time cardiac steady‐state free precession
Authors: Tsao Jeffrey , Kozerke Sebastian , Boesiger Peter , Pruessmann Klaas P. 
Published: May 2005

AbstractIn k‐t BLAST and k‐t SENSE, data acquisition is accelerated by sparsely sampling k‐space over time. This undersampling in k‐t space causes the object signals to be convolved with a point spread function in x‐f space (x = spatial position, f = temporal frequency). The resulting aliasing is resolved by exploiting spatiotemporal correlations within the data. In general, reconstruction accuracy can be improved by controlling the k‐t sampling pattern to minimize signal overlap in x‐f space. In this work, we describe an approach to obtain generally favorable patterns for typical image series without specific knowledge of the image series itself. These optimized sampling patterns were applied to free‐breathing, untriggered (i.e., real‐time) cardiac imaging with steady‐state free precession (SSFP). Eddy‐current artifacts, which are otherwise increased drastically in SSFP by the undersampling, were minimized using alternating k‐space sweeps. With the synergistic combination of the k‐t approach with optimized sampling and SSFP with alternating k‐space sweeps, it was possible to achieve a high signal‐to‐noise ratio, high contrast, and high spatiotemporal resolutions, while achieving substantial immunity against eddy currents. Cardiac images are shown, demonstrating excellent image quality and an in‐plane resolution of ∼2.0 mm at >25 frames/s, using one or more receiver coils. Magn Reson Med 53:1372–1382, 2005. © 2005 Wiley‐Liss, Inc.
PASTA: Pointwise assessment of streamline tractography attributes
Authors: Jones Derek K. , Travis Adam R. , Eden Greg , Pierpaoli Carlo , Basser Peter J. 
Published: May 2005

AbstractDiffusion tensor MRI tractography aims to reconstruct noninvasively the 3D trajectories of white matter fasciculi within the brain, providing neuroscientists and clinicians with a potentially useful tool for mapping brain architecture. While this technique is widely used to visualize white matter pathways, the associated uncertainty in fiber orientation and artifacts have, to date, not been visualized in conjunction with the trajectory data. In this work, the bootstrap method was used to determine the distributions of diffusion indices such as trace and anisotropy, together with the uncertainty in fiber orientation. A novel visualization scheme was developed to encode this information at each point along reconstructed trajectories. By integrating these schemes into a graphical user interface, a new tool which we call PASTA (Pointwise Assessment of Streamline Tractography Attributes) was created to facilitate identification of artifacts in tractography that would otherwise go undetected. Magn Reson Med 53:1462–1467, 2005. Published 2005 Wiley‐Liss, Inc.
Formalin fixation alters water diffusion coefficient magnitude but not anisotropy in infarcted brain
Authors: Sun Shu‐Wei , Neil Jeffrey J. , Liang Hsiao‐Fang , He Yong Y. , Schmidt Robert E. , Hsu Chung Y. , Song Sheng‐Kwei 
Published: May 2005

AbstractThis study was designed to determine whether formalin fixation alters diffusion parameters in the infarcted brain. Diffusion tensor images were obtained from anesthetized mice 1 hr after middle cerebral artery occlusion and repeated after formalin fixation of brains. In live animals, there was a significant decrease in the trace of the diffusion tensor (Tr(D)) in infarcted cortex and external capsule compared with contralateral brain areas, with no change in relative anisotropy (RA). After formalin fixation, Tr(D) was reduced 30–80%. However, the Tr(D) differential present in vivo between injured and healthy tissues was lost, with Tr(D) reduced to similar values in all tissues except for the edge of the cortical infarction, where it was lower than in surrounding tissues. RA values were unchanged after fixation. This study supports the preservation of diffusion anisotropy for both healthy and injured white matter in fixed mouse brain. However, the sensitivity of water diffusion in detecting tissue injury in vivo is not preserved in fixed tissues. Magn Reson Med 53:1447–1451, 2005. © 2005 Wiley‐Liss, Inc.
Spiral balanced steady‐state free precession cardiac imaging
Authors: Nayak Krishna S. , Hargreaves Brian A. , Hu Bob S. , Nishimura Dwight G. , Pauly John M. , Meyer Craig H. 
Published: May 2005

AbstractBalanced steady‐state free precession (SSFP) sequences are useful in cardiac imaging because they achieve high signal efficiency and excellent blood–myocardium contrast. Spiral imaging enables the efficient acquisition of cardiac images with reduced flow and motion artifacts. Balanced SSFP has been combined with spiral imaging for real‐time interactive cardiac MRI. New features of this method to enable scanning in a clinical setting include short, first‐moment nulled spiral trajectories and interactive control over the spatial location of banding artifacts (SSFP‐specific signal variations). The feasibility of spiral balanced SSFP cardiac imaging at 1.5 T is demonstrated. In observations from over 40 volunteer and patient studies, spiral balanced SSFP imaging shows significantly improved contrast compared to spiral gradient‐spoiled imaging, producing better visualization of cardiac function, improved localization, and reduced flow artifacts from blood. Magn Reson Med 53:1468–1473, 2005. © 2005 Wiley‐Liss, Inc.
3Parallel magnetic resonance imaging with adaptive radius in k‐space (PARS): Constrained image reconstruction using k‐space locality in radiofrequency coil encoded data
Authors: Yeh Ernest N. , McKenzie Charles A. , Ohliger Michael A. , Sodickson Daniel K. 
Published: May 2005

AbstractA parallel image reconstruction algorithm is presented that exploits the k‐space locality in radiofrequency (RF) coil encoded data. In RF coil encoding, information relevant to reconstructing an omitted datum rapidly diminishes as a function of k‐space separation between the omitted datum and the acquired signal data. The proposed method, parallel magnetic resonance imaging with adaptive radius in k‐space (PARS), harnesses this physical property of RF coil encoding via a sliding‐kernel approach. Unlike generalized parallel imaging approaches that might typically involve inverting a prohibitively large matrix for arbitrary sampling trajectories, the PARS sliding‐kernel approach creates manageable and distributable independent matrices to be inverted, achieving both computational efficiency and numerical stability. An empirical method designed to measure total error power is described, and the total error power of PARS reconstructions is studied over a range of k‐space radii and accelerations, revealing “minimal‐error” conditions at comparatively modest k‐space radii. PARS reconstructions of undersampled in vivo Cartesian and non‐Cartesian data sets are shown and are compared selectively with traditional SENSE reconstructions. Various characteristics of the PARS k‐space locality constraint (such as the tradeoff between signal‐to‐noise ratio and artifact power and the relationship with iterative parallel conjugate gradient approaches or nonparallel gridding approaches) are discussed. Magn Reson Med 53:1383–1392, 2005. © 2005 Wiley‐Liss, Inc.
Observation of coupled 1H metabolite resonances at long TE
Authors: Soher Brian J. , Pattany Pradip M. , Matson Gerald B. , Maudsley Andrew A. 
Published: May 2005

AbstractA PRESS localization 1H MRS acquisition sequence with a Carr–Purcell train of refocusing pulses (CP‐PRESS) has been implemented using global refocusing “sandwich” pulses. The CP pulse train minimized the effects of J‐coupled dephasing in metabolites with strongly coupled, multiplet resonance groups as demonstrated in both phantom data and in vivo single‐voxel spectroscopy in normal volunteers. Metabolites with multiplet resonance patterns were maintained with greater signal to noise and a simpler resonance pattern at long echo times. T2 decay times for metabolites with singlet and multiplet resonances were similar to published values, except for the NAA multiplet at 2.5 ppm, which had a significantly shorter T2 value (147 ms) than that typically reported for the singlet at 2.01 ppm. Metabolite‐nulled spectra were acquired in normal volunteers to evaluate the effects of CP‐PRESS on baseline signal contributions from residual water, lipids, and macromolecules. The T2 decay times in four baseline regions in data acquired with the CP‐PRESS sequence showed longer decays than corresponding regions in metabolite‐nulled spectra from a standard PRESS sequence, but were significantly diminished long before the metabolites of interest were gone. The spectral analysis for spectra with longer TE times also showed less variability due the higher metabolite SNR, simpler spectral patterns, and the decreased baseline contributions. Magn Reson Med 53:1283–1287, 2005. © 2005 Wiley‐Liss, Inc.
Partial fourier partially parallel imaging
Authors: Bydder Mark , Robson Matthew D. 
Published: May 2005

AbstractThe techniques of partial Fourier (PF) and partially parallel imaging have been combined using a constrained reconstruction technique. The benefits compared with the individual techniques are reduced imaging time and/or an increase in signal‐to‐noise ratio. Low‐resolution phase maps and coil sensitivities may be obtained using autocalibration or from a prescan followed by additional processing. Minor phase artifacts that are introduced by relying on conjugate symmetry can be reduced using a novel regularization scheme to vary the degree to which PF is used in the reconstruction. A nonrectilinear reconstruction algorithm is presented and the potential for motion artifact reduction is investigated using robust reconstruction. Magn Reson Med 53:1393–1401, 2005. © 2005 Wiley‐Liss, Inc.
Isotropic diffusion weighting in radial fast spin‐echo magnetic resonance imaging
Authors: Sarlls Joelle E. , Newbould Rexford D. , Altbach Maria I. , Gmitro Arthur F. , Seeger Joachim , Trouard Theodore P. 
Published: May 2005

AbstractRadial fast spin‐echo (radial‐FSE) methods enable multishot diffusion‐weighted MRI (DWMRI) to be carried out without significant artifacts due to motion and/or susceptibility and can be used to generate DWMRI images with high spatial resolution. In this work, a novel method that allows isotropic diffusion weighting to be obtained in a single radial k‐space data set is presented. This is accomplished by altering the direction of diffusion weighting gradients between groups of TR periods, which yield sets of radial lines that possess diffusion weighting sensitive to motion in different directions. By altering the diffusion weighting directions and controlling the view ordering appropriately within the sequence, an effectively isotropic diffusion‐weighted image can be obtained within one radial‐FSE scan. The order in which radial lines are acquired can also be controlled to yield data sets without significant artifacts due to motion, T2 decay, and/or diffusion anisotropy. Magn Reson Med 53:1347–1354, 2005. © 2005 Wiley‐Liss, Inc.
X‐ray compatible radiofrequency coil for magnetic resonance imaging
Authors: Rieke Viola , Ganguly Arundhuti , Daniel Bruce L. , Scott Greig , Pauly John M. , Fahrig Rebecca , Pelc Norbert J. , Butts Kim 
Published: May 2005

AbstractThe range of RF coils that can be used in combined X‐ray/MR (XMR) systems is limited because many conventional coils contain highly X‐ray attenuating materials that are visible in the X‐ray images and potentially obscure patient anatomy. In this study, an X‐ray compatible coil design that has minimal X‐ray attenuation in the field of view (FOV) of the X‐ray image is presented. In this design, aluminum is used for the loop conductor and discrete elements of the coil are eliminated from the X‐ray FOV. A surface coil and an abdominal phased array coil were built using the X‐ray compatible design. X‐ray attenuation and MR imaging properties of the coils were evaluated and compared to conventional coils. The X‐ray compatible phased array coil was used to image patients during two interventional procedures in the XMR system. The X‐ray compatible coils allowed for fluoroscopic X‐ray image acquisition, without degradation by the coil, while maintaining excellent MR imaging qualities. Magn Reson Med 53:1409–1414, 2005. © 2005 Wiley‐Liss, Inc.
Fast oxygen‐enhanced multislice imaging of the lung using parallel acquisition techniques
Authors: Dietrich Olaf , Losert Christoph , Attenberger Ulrike , Fasol Ulrike , Peller Michael , Nikolaou Konstantin , Reiser Maximilian F. , Schoenberg Stefan O. 
Published: May 2005

AbstractThe purpose of this study was to evaluate an optimized multislice acquisition technique for oxygen‐enhanced MRI of the lung using slice‐selective inversion and refocusing pulses in combination with parallel imaging. An inversion recovery HASTE sequence was implemented with respiratory triggering to perform imaging in end‐expiration and with ECG triggering to avoid image acquisition during the systolic phase. Inversion pulses and the readout of echo trains could be interleaved to decrease acquisition time. The sequence was evaluated in 15 healthy volunteers, comparing three acquisition schemes: (1) acquisition of four slices without parallel imaging; (2) acquisition of four slices with parallel imaging; (3) acquisition of six slices with parallel imaging. These multislice acquisitions were repeated 80 times with alternating inhalation of room air and oxygen. The oxygen‐induced signal increase showed no significant difference with and without parallel imaging. However, only with parallel imaging did the interleaved acquisition of six or more slices become possible, thus enabling a more complete anatomic coverage of the lung. The average required end‐expiration time per repetition to acquire six slices could be significantly reduced from 4112 ms without to 2727 ms with parallel imaging. Total acquisition time varied between 8 and 13 min depending on the respiratory frequency. Magn Reson Med 53:1317–1325, 2005. © 2005 Wiley‐Liss, Inc.
Comparison of [3,4‐13C2]glucose to [6,6‐2H2]glucose as a tracer for glucose turnover by nuclear magnetic resonance
Authors: Jin Eunsook S. , Jones John G. , Burgess Shawn C. , Merritt Matthew E. , Dean Sherry A. , Malloy Craig R. 
Published: May 2005

AbstractA recently introduced tracer, [3,4‐13C2]glucose, was compared to the widely used tracer, [6,6‐2H2]glucose, for measurement of whole‐body glucose turnover. The rate of glucose production (GP) was measured in rats after primed infusions of [3,4‐13C2]glucose, [6,6‐2H2]glucose, or both tracers simultaneously followed by a constant infusion of tracer(s) over 90 min. Blood glucose was purified and converted into monoacetone glucose for analysis by 13C NMR (for [3,4‐13C2]glucose) or 1H and 2H NMR (for [6,6‐2H2]glucose). The values of GP measured during infusion of each single tracer were not significantly different. In rats infused with both tracers simultaneously, GP was identical as reported by each tracer, 42 ± 4 μmol/kg/min. Since 2H and 13C enrichment in glucose is typically much less than 2% for in vivo studies, [3,4‐13C2]glucose does not interfere with measurements of 13C or 2H enrichment patterns and therefore is valuable when multiple metabolic pathways are being evaluated simultaneously. Magn Reson Med 53:1479–1483, 2005. © 2005 Wiley‐Liss, Inc.
Improving the reliability of obtaining tumor hemodynamic parameters in the presence of contrast agent extravasation
Authors: Quarles C. C. , Ward B. D. , Schmainda K. M. 
Published: May 2005

AbstractA new approach to improve the reliability of dynamic susceptibility contrast MRI for the evaluation of brain tumor hemodynamics in the presence of contrast agent extravasation is described. This model‐based technique simultaneously estimates the voxel‐wise tumor residue function and the temporal extravascular T1 changes following contrast agent leakage. With these estimates the model corrects the measured MRI signal, which is then used to calculate tumor hemodynamic parameters. The feasibility of this technique is demonstrated with computer simulations that cover a wide range of hemodynamic conditions and by application to eight tumor‐bearing rats. The simulations demonstrate that the corrected hemodynamic parameters precisely matched the actual values with a maximum percentage error of 4.2% compared to 68.6% for the uncorrected parameters. The corrected parameters are also essentially independent of the tumor hemodynamic state and degree of contrast extravasation. Consistent with these improvements, significant differences between corrected and uncorrected parameters, calculated from a gradient‐echo sequence, are shown in a rat 9L gliosarcoma model. This method combined with the hemodynamic parameters derived from GE and SE sequences shows promise as a new tool to evaluate tumor angiogenesis and its therapy. Magn Reson Med 53:1307–1316, 2005. © 2005 Wiley‐Liss, Inc.