bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunocytochemical and autoradiographic studies on the process of keratinization in avian epidermis suggests absence of keratohyalin
Authors: Alibardi Lorenzo 
Published: January 2004

AbstractThe process of keratinization in apteric avian epidermis and in scutate scales of some avian species has been studied by autoradiography for histidine and immunohistochemistry for keratins and other epidermal proteins. Acidic or basic alpha‐keratins are present in basal, spinosus, and transitional layers, but are not seen in the corneous layer. Keratinization‐specific alpha‐keratins (AE2‐positive) are observed in the corneous layer of apteric epidermis but not in that of scutate scales, which contain mainly beta‐keratin. Alpha‐keratin bundles accumulate along the plasma membrane of transitional cells of apteric epidermis. In contrast to the situation in scutate scales, in the transitional layer and in the lowermost part of the corneous layer of apteric epidermis, filaggrin‐like, loricrin‐like, and transglutaminase immunoreactivities are present. The lack of isopeptide bond immunoreactivity suggests that undetectable isopeptide bonds are present in avian keratinocytes. Using immunogold ultrastructural immunocytochemistry a low but localized loricrin‐like and, less, filaggrin‐like labeling is seen over round‐oval granules or vesicles among keratin bundles of upper spinosus and transitional keratinocytes of apteric epidermis. Filaggrin‐and loricrin‐labeling are absent in alpha‐keratin bundles localized along the plasma membrane and in the corneous layer, formerly considered keratohyalin. Using ultrastructural autoradiography for tritiated histidine, occasional trace grains are seen among these alpha‐keratin bundles. A different mechanism of redistribution of matrix and corneous cell envelope proteins probably operates in avian keratinocytes as compared to that of mammals. Keratin bundles are compacted around the lipid‐core of apteric epidermis keratinocytes, which do not form complex chemico/mechanical‐resistant corneous cell envelopes as in mammalian keratinocytes. These observations suggest that low amounts of matrix proteins are present among keratin bundles of avian keratinocytes and that keratohyalin granules are absent. J. Morphol. 259:238–253, 2004. © 2003 Wiley‐Liss, Inc.
Comparison of Fourier and wavelet resampling methods
Authors: Laird Angela R. , Rogers Baxter P. , Meyerand M. Elizabeth 
Published: January 2004

AbstractResampling can be used to compute the null distribution of any test statistic for the purpose of measuring the significance of the measured value. This study investigated how well the spatial and temporal correlations of simulated and experimentally observed fMRI time series were preserved under Fourier and wavelet resampling methods. The null distributions of a test statistic estimated by each resampling method were compared. In addition, both resampling methods were applied to locate activated voxels in an fMRI dataset and ROC analysis showed that wavelet resampling performed more accurately than Fourier resampling. Magn Reson Med 51:418–422, 2004. © 2004 Wiley‐Liss, Inc.
Biexponential diffusion tensor analysis of human brain diffusion data
Authors: Maier Stephan E. , Vajapeyam Sridhar , Mamata Hatsuho , Westin Carl‐Fredrik , Jolesz Ferenc A. , Mulkern Robert V. 
Published: January 2004

AbstractSeveral studies have shown that in tissues over an extended range of b‐factors, the signal decay deviates significantly from the basic monoexponential model. The true nature of this departure has to date not been identified. For the current study, line scan diffusion images of brain suitable for biexponential diffusion tensor analysis were acquired in normal subjects on a clinical MR system. For each of six noncollinear directions, 32 images with b‐factors ranging from 5 to 5000 s/mm2 were collected. Biexponential fits yielded parameter maps for a fast and a slow diffusion component. A subset of the diffusion data, consisting of the images obtained at the conventional range of b‐factors between 5 and 972 s/mm2, was used for monoexponential diffusion tensor analysis. Fractional anisotropy (FA) of the fast‐diffusion component and the monoexponential fit exhibited no significant difference. FA of the slow‐diffusion biexponential component was significantly higher, particularly in areas of lower fiber density. The principal diffusion directions for the two biexponential components and the monoexponential solution were largely the same and in agreement with known fiber tracts. The second and third diffusion eigenvector directions also appeared to be aligned, but they exhibited significant deviations in localized areas. Magn Reson Med 51:321–330, 2004. © 2004 Wiley‐Liss, Inc.
Fat and water separation in balanced steady‐state free precession using the Dixon method
Authors: Huang Teng‐Yi , Chung Hsiao‐Wen , Wang Fu‐Nien , Ko Cheng‐Wen , Chen Cheng‐Yu 
Published: January 2004

AbstractIn this work the feasibility of separating fat and water signals using the balanced steady‐state free precession (SSFP) technique is demonstrated. The technique is based on the observation (Scheffler and Hennig, Magnetic Resonance in Medicine 2003;49:395–397) that at the nominal values of TE = TR/2 in SSFP imaging, phase coherence can be achieved at essentially only two orientations (0° and 180°) relative to the RF pulses in the rotating frame, under the assumption of TR << T2, and independently of the SSFP angle. This property allows in‐phase and out‐of‐phase SSFP images to be obtained by proper choices of the center frequency offset, and thus allows the Dixon subtraction method to be utilized for effective fat–water separation. The TR and frequency offset for optimal fat–water separation are derived from theories. Experimental results from healthy subjects, using a 3.0 Tesla system, show that nearly complete fat suppression can be accomplished. Magn Reson Med 51:243–247, 2004. © 2004 Wiley‐Liss, Inc.
Longitudinal MRI tracking of the angiogenic response to hind limb ischemic injury in the mouse
Authors: Ziv Keren , Nevo Nava , Dafni Hagit , Israely Tomer , Granot Dorit , Brenner Ori , Neeman Michal 
Published: January 2004

AbstractIschemic injury and revascularization are frequently associated with hyperpermeability. Although extravasation of plasma proteins may promote tissue recovery through the generation of the provisional matrix that supports angiogenesis, edema may also result in progressive damage to the muscle. The aim of this research was to determine the time course of hyperpermeability associated with the angiogenic response induced by ligation of the femoral artery at the right posterior limb in mice. Hyperpermeability was followed noninvasively by MRI using an in‐house‐built permanent polyethylene catheter that enabled daily intravenous administration of biotin‐BSA‐Gd‐DTPA. The mice were scanned once prior to ligation and five times during the week post‐ligation. The MRI data, along with histopathology, indicated that the early hemodynamic compensation over loss of arterial blood supply occurred by angiogenesis and dilation of vessels in the skin and subcutaneous fat, and was accompanied by vascular hyperpermeability around the site of ligation. Functional recovery of the ischemic limb (i.e., regaining the ability to step on the limb), and the color and shape of the toes correlated with regeneration as shown by histopathology and MRI analysis. Thus, MRI provided valuable information on the transient hyperpermeability induced during the early stages of angiogenesis, and its subsequent resolution along with functional recovery from acute hind limb ischemia in mice. Magn Reson Med 51:304–311, 2004. © 2004 Wiley‐Liss, Inc.
Spiral MR myocardial tagging
Authors: Ryf Salome , Kissinger Kraig V. , Spiegel Marcus A. , Börnert Peter , Manning Warren J. , Boesiger Peter , Stuber Matthias 
Published: January 2004

AbstractIn the present study, complementary spatial modulation of magnetization (CSPAMM) myocardial tagging was extended with an interleaved spiral imaging sequence. The use of a spiral sequence enables the acquisition of grid‐tagged images with a tagline distance as low as 4 mm in a single breath‐hold. Alternatively, a high temporal resolution of 77 frames per second was obtained with 8‐mm grid spacing. Ten healthy adult subjects were studied. With this new approach, high‐quality images can be obtained and the tags persist throughout the entire cardiac cycle. Magn Reson Med 51:237–242, 2004. © 2004 Wiley‐Liss, Inc.
Artifact suppression in imaging of myocardial infarction using B1‐weighted phased‐array combined phase‐sensitive inversion recovery†
Authors: Kellman Peter , Dyke Christopher K. , Aletras Anthony H. , McVeigh Elliot R. , Arai Andrew E. 
Published: January 2004

AbstractRegions of the body with long T1, such as cerebrospinal fluid (CSF), may create ghost artifacts on gadolinium‐hyperenhanced images of myocardial infarction when inversion recovery (IR) sequences are used with a segmented acquisition. Oscillations in the transient approach to steady state for regions with long T1 may cause ghosts, with the number of ghosts being equal to the number of segments. B1‐weighted phased‐array combining provides an inherent degree of ghost artifact suppression because the ghost artifact is weighted less than the desired signal intensity by the coil sensitivity profiles. Example images are shown that illustrate the suppression of CSF ghost artifacts by the use of B1‐weighted phased‐array combining of multiple receiver coils. Magn Reson Med 51:408–412, 2004. Published 2004 Wiley‐Liss, Inc.
Comparison of FAIR perfusion kinetics with DSC‐MRI and functional histology in a model of transient ischemia
Authors: Schepers Janneke , Veldhuis Wouter B. , Pauw Robert‐Jan , de Groot Jan‐Willem , van Osch Matthias J.P. , Nicolay Klaas , van der Sanden Boudewijn P.J. 
Published: January 2004

AbstractFlow‐sensitive alternating inversion recovery (FAIR) is a noninvasive method for perfusion imaging. It has been shown that the FAIR signal may depend on hemodynamic parameters other than perfusion, the most important one being transit delays of labeled spins to the observed tissue. These parameters are expected to change with ischemia. The goal of this study was to assess the effect of these changes on the interpretation of FAIR results in the case of altered perfusion. This was investigated in a rat model of transient cerebral ischemia. It was shown that the ratio of FAIR signal in the infarct compared to the contralateral side was lower at short inflow times, which suggests that transit times affected the effective FAIR signal. The FAIR results were compared with those from functional histology and dynamic susceptibility contrast MRI, and the findings indicated that the altered kinetics of the FAIR signal were related to reduced and delayed inflow in the infarct region—not to a decrease in the number of functional vessels. Magn Reson Med 51:312–320, 2004. © 2004 Wiley‐Liss, Inc.
Noquist: Reduced field‐of‐view imaging by direct Fourier inversion
Authors: Brummer Marijn E. , Moratal‐Pérez David , Hong Chung‐Yi , Pettigrew Roderic I. , Millet‐Roig José , Dixon W. Thomas 
Published: January 2004

AbstractA novel technique called “Noquist” is introduced for the acceleration of dynamic cardiac magnetic resonance imaging (CMRI). With the use of this technique, a more sparsely sampled dynamic image sequence is reconstructed correctly, without Nyquist foldover artifact. Unlike most other reduced field‐of‐view (rFOV) methods, Noquist does not rely on data substitution or temporal interpolation to reconstruct the dynamic image sequence. The proposed method reduces acquisition time in dynamic MRI scans by eliminating the data redundancy associated with static regions in the dynamic scene. A reduction of imaging time is achieved by a fraction asymptotically equal to the static fraction of the FOV, by omitting acquisition of an appropriate subset of phase‐encoding views from a conventional equidistant Cartesian acquisition grid. The theory behind this method is presented along with sample reconstructions from real and simulated data. Noquist is compared with conventional cine imaging by retrospective selection of a reduced data set from a full‐grid conventional image sequence. In addition, a comparison is presented, using real and simulated data, of our technique with an existing rFOV technique that uses temporal interpolation. The experimental results confirm the theory, and demonstrate that Noquist reduces scan time for cine MRI while fully preserving both spatial and temporal resolution, but at the cost of a reduced signal‐to‐noise ratio (SNR). Magn Reson Med 51:331–342, 2004. © 2004 Wiley‐Liss, Inc.
Strategy for the spectral filtering of myo‐inositol and other strongly coupled spins
Authors: Kim Hyeonjin , Wild James M. , Allen Peter S. 
Published: January 2004

AbstractA multiple quantum filter strategy is presented for spectrally discriminating metabolites with strongly coupled spins from those whose spins are either uncoupled or weakly coupled. The strategy also includes a means for selectively suppressing the background multiplets of metabolites that also have strongly coupled spins. As a demonstration of its efficacy at 3.0 T, the strategy is shown to enhance by a factor of ∼5 the signal‐to‐background ratio of the myo‐inositol band at 3.6 ppm relative to that in response to a PRESS sequence with the same sequence timings. This is done by eliminating the uncoupled resonance of glycine and the weakly coupled multiplets of glutamate and glutamine, and by selectively suppressing the strongly coupled taurine multiplet 3‐fold. The macromolecular background was effectively removed through its transverse decay over 105 ms. The associated cost of gaining the signal to background enhancement is a drop in signal yield by a factor of 0.75 relative to PRESS at the same timings. The myo‐inositol signal to noise ratio was nevertheless maintained by the filter at ∼12. Magn Reson Med 51:263–272, 2004. © 2004 Wiley‐Liss, Inc.
Detection of simulated pulmonary embolism in a porcine model using hyperpolarized 3He MRI
Authors: Jalali Aman , Ishii Masaru , Edvinsson Johan M. , Guan Liang , Itkin Maxim , Lipson David A. , Baumgardner James E. , Rizi Rahim R. 
Published: January 2004

AbstractSeveral radiological imaging modalities are available to assist with the clinical diagnosis of pulmonary embolism (PE). The most frequently used techniques—nuclear medicine ventilation‐perfusion (VP) scan, computed tomography (CT), magnetic resonance angiography (MRA), and pulmonary angiography (PA)—all have literature‐supported, substantial limitations with respect to timeliness and patient safety. Hyperpolarized 3He magnetic resonance gas distribution imaging (HP 3He MRI) recently has shown potential as a safer and faster alternative. In this study, we performed HP 3He MRI on a porcine model (N = 6) of simulated PE using selective occlusion balloon catheterization (N = 4) and nonselective aged autologous clot injection (N = 1). The technique was also performed on a normal pig and again after the animal was killed. Temporal depletion of regional HP 3He MRI signal intensity provided for a qualitative assessment of simulated PE (N = 4), and regional PAO2 (alveolar partial pressure of oxygen) was calculated in affected airspaces for a quantitative assessment of simulated PE (N = 1). The preliminary results suggest that HP 3He MRI shows promise as a means of assessing regional pulmonary perfusion abnormalities in the porcine models of simulated PE that were used in this study. Magn Reson Med 51:291–298, 2004. © 2004 Wiley‐Liss, Inc.
Regional variations in normal brain shown by quantitative magnetization transfer imaging
Authors: Sled J.G. , Levesque I. , Santos A.C. , Francis S.J. , Narayanan S. , Brass S.D. , Arnold D.L. , Pike G.B. 
Published: January 2004

AbstractA quantitative magnetization transfer imaging (qMTI) study, based on a two‐pool model of magnetization transfer, was performed on seven normal subjects to determine, on a regional basis, normal values for the pool sizes, exchange, and relaxation parameters that characterize the MT phenomenon. Regions were identified on high‐resolution anatomical scans using a combination of manual and automatic methods. Only voxels identified as pure tissue at the resolution of the quantitative scans were considered for analysis. While no left/right differences were observed, significant differences were found among white‐matter regions and gray‐matter regions. These regional differences were compared with existing cytoarchitectural data. In addition, the pattern and magnitude of the regional differences observed in white matter was found to be different from that reported previously for an alternative putative MRI measure of myelination, the 10–50‐ms T2 component described as myelin water. Magn Reson Med 51:299–303, 2004. © 2004 Wiley‐Liss, Inc.
The existence of biexponential signal decay in magnetic resonance diffusion‐weighted imaging appears to be independent of compartmentalization
Authors: Schwarcz Attila , Bogner Peter , Meric Philippe , Correze Jean‐Loup , Berente Zoltan , Pál József , Gallyas Ferenc , Doczi Tamas , Gillet Brigitte , Beloeil Jean‐Claude 
Published: January 2004

AbstractIt is generally believed that the apparent diffusion coefficient (ADC) changes measured by diffusion‐weighted imaging (DWI) in brain pathologies are related to alterations in the water compartments. The aim of this study was to elucidate the role of compartmentalization in DWI via biexponential analysis of the signal decay due to diffusion. DWI experiments were performed on mouse brain over an extended range of b‐values (up to 10000 mm–2 s) under intact, global ischemic, and cold‐injury conditions. DWI was additionally applied to centrifuged human erythrocyte samples with a negligible extracellular space. Biexponential signal decay was found to occur in the cortex of the intact mouse brain. During global ischemia, in addition to a drop in the ADC in both components, a shift from the volume fraction of the rapidly diffusing component to the slowly diffusing one was observed. In cold injury, the biexponential signal decay was still present despite the electron‐microscopically validated disintegration of the membranes. The biexponential function was also applicable for fitting of the data obtained on erythrocyte samples. The results suggest that compartmentalization is not an essential feature of biexponential decay in diffusion experiments. Magn Reson Med 51:278–285, 2004. © 2004 Wiley‐Liss, Inc.
Floating navigator echo (FNAV) for in‐plane 2D translational motion estimation
Authors: Kadah Yasser M. , Abaza Ayman A. , Fahmy Ahmed S. , Youssef Abou‐Bakr M. , Heberlein Keith , Hu Xiaoping P. 
Published: January 2004

AbstractA modification of the classical navigator echo (NAV) technique is presented whereby both 2D translational motion components are computed from a single navigator line. Instead of acquiring the NAV at the center of thek‐space, akxline is acquired off‐center in the phase‐encoding (ky) direction as a floating NAV (FNAV). It is shown that the translational motion in both the readout and phase‐encoding directions can be computed from this line. The algorithm used is described in detail and verified experimentally. The new technique can be readily implemented to replace classic NAV in MRI sequences, with little to no additional cost or complexity. The new method can help suppress 2D translational motion and provide more accurate motion estimates for other motion‐suppression techniques, such as the diminishing variance algorithm. Magn Reson Med 51:403–407, 2004. © 2004 Wiley‐Liss, Inc.
Pulse sequence for multislice T1ρ‐weighted MRI
Authors: Wheaton Andrew J. , Borthakur Arijitt , Charagundla Sridhar R. , Reddy Ravinder 
Published: January 2004

AbstractA 2D multislice spin‐lock (MS‐SL) MR pulse sequence is presented for rapid volumetric T1ρ‐weighted imaging. Image quality is compared with T1ρ‐weighted data collected using a single‐slice (SS) SL sequence and T2‐weighted data from a standard MS spin‐echo (SE) sequence. Saturation of longitudinal magnetization by the application of nonselective SL pulses is experimentally measured and theoretically modeled as T2ρ decay. The saturation data is used to correct the image data as a function of the SL pulse duration to make quantitative measurements of T1ρ. Measurements of T1ρ using the saturation‐corrected MS‐SL data are nearly identical to those measured using an SS‐SL sequence. The MS‐SL sequence produces quantitative T1ρ maps of an entire sample volume with the high‐SNR advantages conferred by SE‐based sequences. Magn Reson Med 51:362–369, 2004. © 2004 Wiley‐Liss, Inc.
Event‐related fMRI technique for auditory processing with hemodynamics unrelated to acoustic gradient noise
Authors: Schmithorst Vincent J. , Holland Scott K. 
Published: January 2004

AbstractAcoustic noise from the imaging gradients presents a major difficulty in functional MRI (fMRI) studies of auditory cortical function. For studies involving hearing‐impaired pediatric subjects, the auditory stimuli should be presented during completely silent gradient intervals. In addition, the scan time is limited by constraints involving subject motion and subject compliance. A novel event‐related method for conducting fMRI studies of auditory function is proposed. Auditory stimuli are presented during completely silent gradient intervals, but using a variable TR. A general nonlinear model (GNLM) is proposed as a postprocessing methodology for the data. The technique increases the flexibility of the experimental design, with minimal loss of sensitivity compared to standard fMRI acquisition techniques, and may therefore be useful for fMRI studies of auditory function in hearing‐impaired pediatric subjects. Magn Reson Med 51:399–402, 2004. © 2004 Wiley‐Liss, Inc.
SENSE‐DTI at 3 T
Authors: Jaermann T. , Crelier G. , Pruessmann K.P. , Golay X. , Netsch T. , van Muiswinkel A.M.C , Mori S. , van Zijl P.C.M. , Valavanis A. , Kollias S. , Boesiger P. 
Published: January 2004

AbstractWhile holding vast potential, diffusion tensor imaging (DTI) with single‐excitation protocols still faces serious challenges. Limited spatial resolution, susceptibility to magnetic field inhomogeneity, and low signal‐to‐noise ratio (SNR) may be considered the most prominent limitations. It is demonstrated that all of these shortcomings can be effectively mitigated by the transition to parallel imaging technology and high magnetic field strength. Using the sensitivity encoding (SENSE) technique at 3 T, brain DTI was performed in nine healthy volunteers. Despite enhanced field inhomogeneity, parallel acquisition permitted both controlling geometric distortions and enhancing spatial resolution up to 0.8 mm in‐plane. Heightened SNR requirements were met in part by high base sensitivity at 3 T. A further significant increase in SNR efficiency was accomplished by SENSE acquisition, exploiting enhanced encoding speed for echo time reduction. Based on the resulting image data, high‐resolution tensor mapping is demonstrated. Magn Reson Med 51:230–236, 2004. © 2004 Wiley‐Liss, Inc.