bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single‐shot magnetic field mapping embedded in echo‐planar time‐course imaging
Authors: Roopchansingh Vinai , Cox Robert W. , Jesmanowicz Andrzej , Ward B. Douglas , Hyde James S. 
Published: September 2003

AbstractA technique for acquiring magnetic field maps simultaneously with gradient‐recalled echo‐planar time‐course data is described. This technique uses a trajectory in which the central part of k‐space is collected twice. For a 64 × 64 image acquired with a 125‐kHz bandwidth, a field map suitable for geometric correction can be collected simultaneously with the echo‐planar time‐course data in <70 ms. The field maps generated by this technique are registered with the magnitude images because they are calculated using the same data. They do not suffer from errors due to subject motion, or from different geometric distortions that can result from using different pulse sequences. In addition to correcting geometric distortions that resulted from dynamic magnetic field perturbations, this method was used to measure field shifts arising from respiration and jaw motion across five subjects. Values ranged from 0.035 to 0.165 parts per million (ppm). Magn Reson Med 50:839–843, 2003. © 2003 Wiley‐Liss, Inc.
Electrical conductivity imaging by magnetic resonance electrical impedance tomography (MREIT)
Authors: Oh Suk H. , Han Jae Y. , Lee Soo Y. , Cho Min H. , Lee Byung I. , Woo Eung J. 
Published: September 2003

AbstractMagnetic resonance electrical impedance tomography (MREIT) is a recently developed imaging technique that combines MRI and electrical impedance tomography (EIT). In MREIT, cross‐sectional electrical conductivity images are reconstructed from the internal magnetic field density data produced inside an electrically conducting subject when an electrical current is injected into the subject. In this work the results of an electrical conductivity imaging experiment are presented, along with some practical considerations regarding MREIT. The MREIT experiment was performed with a 0.3 Tesla MRI system on a phantom made of two compartments with different electrical conductivities. The current density inside the phantom was measured by the MR current density imaging (MRCDI) technique. The measured current density was then used for conductivity image reconstruction by the J‐substitution algorithm. The conductivity phantom images obtained with an injection current of 28mA showed conductivity errors of about 25.5%. Magn Reson Med 50:875–878, 2003. © 2003 Wiley‐Liss, Inc.
Importance of k‐space trajectory in echo‐planar myocardial tagging at rest and during dobutamine stress
Authors: Kim Daniel , Bove Christina M. , Kramer Christopher M. , Epstein Frederick H. 
Published: September 2003

AbstractHybrid fast gradient echo/echo‐planar imaging (FGRE‐EPI) can be used to increase temporal resolution, enhance tag contrast, and/or decrease scan time for breathhold myocardial tagging. However, off‐resonance effects and motion can lead to local phase discontinuities in FGRE‐EPI raw data when a conventional interleaved bottom‐up k‐space trajectory is used. These discontinuities can be particularly problematic for myocardial tagging, where the image energy is not only concentrated near the k‐space origin, but is also concentrated in multiple spectral peaks centered throughout k‐space. In this study, tag distortion artifacts in FGRE‐EPI tagging due to off‐resonance and velocity‐induced phase discontinuities were characterized at rest and dobutamine stress, and the flyback and gradient moment smoothing (GMS) methods were shown to reduce these artifacts. For the specific parameters used in this study, flyback and GMS resulted in improved image quality at rest and stress, increased myocardium‐tag contrast‐to‐noise ratio (11.4 ± 2.1 vs. 10.0 ± 2.9, P < 0.01 at rest; 11.1 ± 1.8 vs. 8.1 ± 2.4, P < 0.01 at stress), and reduced full width at half maximum of the tag profile (3.6 vs. 3.8 pixels at rest; 4.0 vs. 5.1 pixels at stress) compared to the conventional trajectory. A limitation of the improved trajectory is a parameter‐dependent decrease in data acquisition efficiency. For the specific imaging protocol used, the repetition time of the improved trajectory increased by 36% compared to the conventional trajectory. Magn Reson Med 50:813–820, 2003. © 2003 Wiley‐Liss, Inc.
Dynamic 3He imaging for quantification of regional lung ventilation parameters
Authors: Dupuich David , Berthezène Yves , Clouet Pierre‐Louis , Stupar Vasile , Canet Emmanuelle , Crémillieux Yannick 
Published: September 2003

AbstractDynamic ventilation imaging using laser‐polarized 3He has a promising potential for elucidating the physiology and physiopathology of the lungs. In this study, a methodological approach is proposed for the assessment and quantification of local ventilation parameters. High‐temporal‐resolution coronal ventilation image series were obtained with a projection‐reconstruction (PR) sequence combined with the sliding‐window technique. After image series were processed, parametric pixel‐by‐pixel maps of the gas arrival time, filling time constant, inflation rate, and gas volume were generated. The acquisition technique and the signal processing procedure, which are referred to collectively as sliding pulmonary imaging for respiratory overview (SPIRO), were tested in vivo in healthy rat lungs using a contrast media injector for controlled 3He flow and volume injection in the animal lungs. The same protocol was applied to broncho‐constriction animal models using intravenous injection of methacholine solution. Inflation rate values measured in the lungs were found to decrease with increasing doses of injected methacholine solution. This study demonstrates that it is possible to obtain quantitative regional gas dynamic information using the SPIRO technique in a single polarized gas inspiration. Magn Reson Med 50:777–783, 2003. © 2003 Wiley‐Liss, Inc.
Cerebral blood volume measurements by T‐weighted MRI and contrast infusion
Authors: Newman G.C. , Delucia‐Deranja E. , Tudorica A. , Hospod F.E. , Patlak C.S. 
Published: September 2003

AbstractA reliable, accurate, and accessible method for measuring cerebral blood volume (CBV) has been developed based on T‐weighted MRI and a 1‐min infusion of gadolinium instead of a bolus. Computer simulations predict that this infusion CBV method will have a signal‐to‐noise ratio (SNR) 3–5 times greater than that obtained by area‐under‐the‐curve (AUC) methods, with high accuracy over a wide range of arterial, tissue, and MRI conditions. In six healthy controls, the CBV was 1.87 ± 0.44 in white matter (WM), 3.40 ± 0.44 in deep gray matter (DGM), and 3.84 ± 1.87 ml blood/100 g tissue in cortical GM (CGM). The mean GM/WM ratio was 1.94. In five patients with bilateral carotid disease, the corresponding values were 2.63 ± 0.33, 4.72 ± 0.33, and 5.27 ± 2.40 ml blood/100 g tissue, all of which were significantly different from controls. AUC values were generally higher and failed to demonstrate differences between controls and patients. The infusion method shows great potential for providing reliable, accurate, and accessible CBV values with the ability to discriminate physiologic or pathological volume changes under a wide range of conditions. Magn Reson Med 50:844–855, 2003. © 2003 Wiley‐Liss, Inc.
High‐resolution diffusion‐weighted 3D MRI, using diffusion‐weighted driven‐equilibrium (DW‐DE) and multishot segmented 3D‐SSFP without navigator echoes
Authors: Jeong Eun‐Kee , Kim Seong‐Eun , Parker Dennis L. 
Published: September 2003

AbstractIn this work we report on the development of a novel technique for high‐resolution diffusion‐weighted (DW) MRI based upon 3D steady‐state free precession (3D‐SSFP). First the 3D‐SSFP acquisition was segmented (each segment consisting of a series of RF pulses and gradient‐recalled echoes), and then DW‐driven equilibrium (DE) was inserted between each segment. The in‐plane imaging matrix was typically 256 × 192 or 256 × 160, which resulted in high‐resolution DW images. The DW‐DE segmented SSFP signal was contaminated by the non‐DW magnetization, which recovered and contributed signal during the readout train (T1 contamination). Center‐out slice encoding was used to place the greatest diffusion weighting at the center of k‐space. A numerical simulation and supporting experiments were performed to evaluate the relationship of the transverse magnetization to imaging parameters, such as the b‐value, echo‐train length (ETL), echo‐train (group) repetition time (TRg), and RF excitation TR (Δt). Both the numerical simulation and the experiments suggested that the effect of T1 contamination would be reduced with a longer TRg, smaller b‐value, shorter ETL, and center‐out slice phase encoding. Phase errors caused by microscopic motions during the diffusion gradients were converted into amplitude errors by the tip‐up pulse at the end of the diffusion‐weighting segment. As a result, small bulk motions, such as CSF pulsation, did not cause motion‐related ghosting artifacts, which would be typical in images from other multishot DWI techniques. This technique can be used for high‐resolution DWI of nonbrain anatomies. Magn Reson Med 50: 821–829, 2003. © 2003 Wiley‐Liss, Inc.
Application of continuous‐wave EPR spectral‐spatial image reconstruction techniques for in vivo oxymetry: Comparison of projection reconstruction and constant‐time modalities
Authors: Matsumoto Ken‐ichiro , Chandrika Baby , Lohman Joost A.B. , Mitchell James B. , Krishna Murali C. , Subramanian Sankaran 
Published: September 2003

AbstractIn this study we report the application of continuous‐wave (CW) electron paramagnetic resonance (EPR) constant‐time spectral spatial imaging (CTSSI) for in vivo oxymetry. 2D and 3D SSI studies of a phantom and live mice were carried out using projection reconstruction (PR) and constant‐time (CT) modalities using a CW‐EPR spectrometer/imager operating at 300 MHz frequency. Distortion of line shape, which is inherent in the PR method, was minimized by the CTSSI modality. It was also found that CTSSI offers improved noise reduction, restores a smoother line shape, and gives high convergence of estimated values. Spatial resolution was also improved by CTSSI, although fundamental spectral line‐width broadening was observed. Although additional corrections are required for accurate estimations of spectral line width, CTSSI was able to demonstrate distinct differences in oxygen tension between a tumor and the normal legs of a C3H mouse. The PR method, on the other hand, was unable to make such a distinction unequivocally with the triarylmethyl spin probes. CTSSI promises to be a more suitable method for quantitative in vivo oxymetric studies using radiofrequency EPR imaging (EPRI). Magn Reson Med 50:865–874, 2003. Published 2003 Wiley‐Liss, Inc.
Independent component analysis for automated decomposition of in vivo magnetic resonance spectra
Authors: Ladroue Christophe , Howe Franklyn A. , Griffiths John R. , Tate A. Rosemary 
Published: September 2003

AbstractFully automated methods for analyzing MR spectra would be of great benefit for clinical diagnosis, in particular for the extraction of relevant information from large databases for subsequent pattern recognition analysis. Independent component analysis (ICA) provides a means of decomposing signals into their constituent components. This work investigates the use of ICA for automatically extracting features from in vivo MR spectra. After its limits are assessed on artificial data, the method is applied to a set of brain tumor spectra. ICA automatically, and in an unsupervised fashion, decomposes the signals into interpretable components. Moreover, the spectral decomposition achieved by the ICA leads to the separation of some tissue types, which confirms the biochemical relevance of the components. Magn Reson Med 50:697–703, 2003. © 2003 Wiley‐Liss, Inc.
Reproducibility of 1H‐MRS measurements in schizophrenic patients
Authors: Mullins Paul G. , Rowland Laura , Bustillo Juan , Bedrick Edward J. , Lauriello John , Brooks William M. 
Published: September 2003

AbstractThe reproducibility of single‐voxel spectroscopic measures in a stable schizophrenic patient population is reported. Spectra acquired 1 week apart, in the left frontal white matter and left caudate nucleus of 12 patients, were analyzed using both frequency and time‐domain techniques. No significant change in mean concentrations for N‐acetylaspartate (NAA), choline (Cho), and creatine (Cre) were found between sessions. Variation from scan to scan was low for the left frontal white matter, with coefficients of variation (CV) < 5% for all three metabolites. NAA measures from the left caudate nucleus had similar reproducibility (CV = 5%), but Cho and Cre were poorer by comparison (CV = 16–18%). The two methods used for spectral analyses produced similar results, indicating that both techniques are appropriate. These results extend previous studies of healthy, normal subjects, and establish that it is possible to obtain reliable measures of brain metabolites in clinical populations. Magn Reson Med 50:704–707, 2003. © 2003 Wiley‐Liss, Inc.
A PRESTO‐SENSE sequence with alternating partial‐Fourier encoding for rapid susceptibility‐weighted 3D MRI time series
Authors: Klarhöfer Markus , Dilharreguy Bixente , van Gelderen Peter , Moonen Chrit T.W. 
Published: September 2003

AbstractA 3D sequence for dynamic susceptibility imaging is proposed which combines echo‐shifting principles (such as PRESTO), sensitivity encoding (SENSE), and partial‐Fourier acquisition. The method uses a moderate SENSE factor of 2 and takes advantage of an alternating partial k‐space acquisition in the “slow” phase encode direction allowing an iterative reconstruction using high‐resolution phase estimates. Offering an isotropic spatial resolution of 4 × 4 × 4 mm3, the novel sequence covers the whole brain including parts of the cerebellum in 0.5 sec. Its temporal signal stability is comparable to that of a full‐Fourier, full‐FOV EPI sequence having the same dynamic scan time but much less brain coverage. Initial functional MRI experiments showed consistent activation in the motor cortex with an average signal change slightly less than that of EPI. Magn Reson Med 50:830–838, 2003. © 2003 Wiley‐Liss, Inc.
High flip angle imaging of metallic stents: Implications for MR angiography and intraluminal signal interpretation
Authors: van Holten Jacqueline , Wielopolski Piotr , Brück Ekkes , Pattynama Peter M.T. , van Dijk Lukas C. 
Published: September 2003

AbstractIntraluminal stent signal characterization by MRI is generally hampered by signal loss from the metallic stent material. This signal loss is related to magnetic susceptibility and RF shielding. Even when stent materials with low magnetic susceptibility are used, RF shielding can still be problematic. In this article we have shown that high flip angle imaging enables morphology assessment and tissue characterization in stents made of stainless steel 316L, NiTinol, and ABI‐alloy. Magn Reson Med 50:879–883, 2003. © 2003 Wiley‐Liss, Inc.
1H‐localized broadband 13C NMR spectroscopy of the rat brain in vivo at 9.4 T
Authors: Henry Pierre‐Gilles , Tkáč Ivan , Gruetter Rolf 
Published: September 2003

AbstractLocalized 13C NMR spectra were obtained from the rat brain in vivo over a broad spectral range (15–100 ppm) with minimal chemical‐shift displacement error (<10%) using semi‐adiabatic distortionless enhancement by polarization transfer (DEPT) combined with 1H localization. A new gradient dephasing scheme was employed to eliminate unwanted coherences generated by DEPT when using surface coils with highly inhomogeneous B1 fields. Excellent sensitivity was evident from the simultaneous detection of natural abundance signals for N‐acetylaspartate, myo‐inositol, and glutamate in the rat brain in vivo at 9.4 T. After infusion of 13C‐labeled glucose, up to 18 13C resonances were simultaneously measured in the rat brain, including glutamate C2, C3, C4, glutamine C2, C3, C4, aspartate C2, C3, glucose C1, C6, N‐acetyl‐aspartate C2, C3, C6, as well as GABA C2, lactate C3, and alanine C3. 13C‐13C multiplets corresponding to multiply labeled compounds were clearly observed, suggesting that extensive isotopomer analysis is possible in vivo. This unprecedented amount of information will be useful for metabolic modeling studies aimed at understanding brain energy metabolism and neurotransmission in the rodent brain. Magn Reson Med 50:684–692, 2003. © 2003 Wiley‐Liss, Inc.
Functional brain imaging using a blood oxygenation sensitive steady state
Authors: Miller Karla L. , Hargreaves Brian A. , Lee Jongho , Ress David , Christopher deCharms R. , Pauly John M. 
Published: September 2003

AbstractBlood oxygenation level dependent (BOLD) functional MRI (fMRI) is an important method for functional neuroimaging that is sensitive to changes in blood oxygenation related to brain activation. While BOLD imaging has good spatial coverage and resolution relative to other neuroimaging methods (such as positron emission tomography (PET)), it has significant limitations relative to other MRI techniques, including poor spatial resolution, low signal levels, limited contrast, and image artifacts. These limitations derive from the coupling of BOLD functional contrast to sources of image degradation. This work presents an alternative method for fMRI that may over‐come these limitations by establishing a blood oxygenation sensitive steady‐state (BOSS) that inverts the signal from deoxygenated blood relative to the water signal. BOSS fMRI allows the imaging parameters to be optimized independently of the functional contrast, resulting in fewer image artifacts and higher signal‐to‐noise ratio (SNR). In addition, BOSS fMRI has greater functional contrast than BOLD. BOSS fMRI requires careful shimming and multiple acquisitions to obtain a precise alignment of the magnetization to the SSFP frequency response. Magn Reson Med 50:675–683, 2003. © 2003 Wiley‐Liss, Inc.
Neurobehavioral effects among subjects exposed to high static and gradient magnetic fields from a 1.5 Tesla magnetic resonance imaging system—A case‐crossover pilot study
Authors: de Vocht Frank , van‐Wendel‐de‐Joode Berna , Engels Hans , Kromhout Hans 
Published: September 2003

AbstractThe interactive use of magnetic resonance imaging (MRI) techniques is increasing in operating theaters. A study was performed on 17 male company volunteers to assess the neurobehavioral effects of exposure to magnetic fields from a 1.5 Tesla MRI system. The subjects' neurobehavioral performances on a neurobehavioral test battery were compared in four 1‐hr sessions with and without exposure to magnetic fields, and with and without additional movements. Adverse effects were found for hand coordination (–4%, P < 0.05; Pursuit Aiming II) and near visual contrast sensitivity (–16% and –15%, P < 0.10; Vistech 6000™). The results from the remaining tests were inconclusive due to a strong learning effect. No additional effect from gradient fields was detected. The results indicate that working near a 1.5 Tesla MRI system may lead to neurobehavioral effects. Further research is recommended, especially in members of operating teams using interactive MRI systems. Magn Reson Med 50:670–674, 2003. © 2003 Wiley‐Liss, Inc.
Relative indices of water diffusion anisotropy are equivalent in live and formalin‐fixed mouse brains
Authors: Sun Shu‐Wei , Neil Jeffrey J. , Song Sheng‐Kwei 
Published: September 2003

AbstractFormalin fixation of tissue is a common laboratory practice. A direct comparison of diffusion tensor imaging (DTI) parameters from mouse brains before (in vivo) and after (ex vivo) formalin fixation is reported herein. Five diffusion indices were examined in a cohort of seven mice: relative anisotropy (RA), directional correlation (DC), trace (Tr(D)), trace‐normalized axial diffusivity (D∥), and radial diffusivity (D⟂). Seven regions of interest (ROIs), including five in white matter and two in gray matter, were selected for examination. Consistent with previous findings, a significant decrease of Tr(D) was observed for all ROIs after fixation. However, water diffusion anisotropy, as defined by the indices RA, DC, D∥, and D⟂, remained unchanged after fixation. Thus, fixation does not appear to alter diffusion anisotropy in the mouse brain. This finding supports the utility of diffusion anisotropy analysis of fixed tissue. The combination of DTI measurements and standard histology may shed light on the microstructural determinants of diffusion anisotropy in normal and disease states. Magn Reson Med 50:743–748, 2003. © 2003 Wiley‐Liss, Inc.
Normative pediatric brain data for spatial normalization and segmentation differs from standard adult data
Authors: Wilke M. , Schmithorst V.J. , Holland S.K. 
Published: September 2003

AbstractSpatial normalization and morphological studies of pediatric brain imaging data based on adult reference data may not be appropriate due to the developmental differences between the two populations. In this study, we set out to create pediatric templates and a priori brain tissue data from a large collection of normal, healthy children to compare it to standard adult data available within a widely used imaging software solution (SPM99, WDOCN, London, UK). Employing four different processing strategies, we found considerable differences between our pediatric data and the adult data. We conclude that caution should be used when analyzing pediatric brain data using adult a priori information. To assess the effects of using pediatric a priori brain information, the data obtained in this study is available to the scientific community from our website (www.irc.cchmc.org). Magn Reson Med 50:749–757, 2003. © 2003 Wiley‐Liss, Inc.
Effects of tracer arrival time on flow estimates in MR perfusion‐weighted imaging
Authors: Wu Ona , Østergaard Leif , Koroshetz Walter J. , Schwamm Lee H. , O'Donnell Joanie , Schaefer Pamela W. , Rosen Bruce R. , Weisskoff Robert M. , Sorensen A. Gregory 
Published: September 2003

AbstractA common technique for calculating cerebral blood flow (CBF) and mean transit time (MTT) is to track a bolus of contrast agent using perfusion‐weighted MRI (PWI) and to deconvolve the change in concentration with an arterial input function (AIF) using singular value decomposition (SVD). This method has been shown to often overestimate the volume of tissue that infarcts and in cases of severe vasculopathy to produce CBF maps that are inconsistent with clinical presentation. This study examines the effects of tracer arrival time differences between tissue and a user‐selected global AIF on flow estimates. CBF and MTT were calculated in both numerically simulated and clinically acquired PWI data where the AIF and tissue signals were shifted backward and forward in time with respect to one another. Results show that when the AIF leads the tissue, CBF is underestimated independent of extent of delay, but dependent on MTT. When the AIF lags the tissue, flow may be over‐ or underestimated depending on MTT and extent of timing differences. These conditions may occur in practice due to the application of a user‐selected AIF that is not the “true AIF” and therefore caution must be taken in interpreting CBF and MTT estimates. Magn Reson Med 50:856–864, 2003. © 2003 Wiley‐Liss, Inc.
Light Scattering by Bent Cylindrical Fibers for Fiber Length and Diameter Characterization
Authors: Schuh Roman , Wriedt Thomas 
Published: September 2003

AbstractLight scattering computations for cylindrical fibers of high aspect ratios are needed in designing instruments for the optical characterization of airborne fibers. Long airborne fibers may also appear in a bent shape. In this paper computational results for bent fibers of various radii of bending will be presented using the multiple multipole technique (MMP).