bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo monitoring of hepatic oxygenation changes in chronically ethanol‐treated rats by functional magnetic resonance imaging
Authors: Foley Lesley M. , Picot Paul , Thompson R. Terry , Yau Melissa J. , Brauer Manfred 
Published: October 2003

AbstractIn this study, functional magnetic resonance imaging (fMRI) was used to evaluate in vivo hepatic oxygenation changes in chronically ethanol (CE)‐treated and pair‐fed (PF) control rats. Male Wistar rats were pair‐fed an all‐liquid diet containing 36% of total calories as either ethanol or dextrin‐maltose for 8 weeks. The rats were initially examined under normoxic conditions, and then subjected to 100% oxygen (hyperoxia), 10% oxygen (hypoxia), 5% carbon dioxide (hypercapnia), or an acute dose of ethanol (1.4 g/kg bw intraperitoneally). A T2‐weighted spin‐echo sequence, which may be more selective for sinusoidal (capillary bed) changes, was performed before, during, and after the four challenges. During hyperoxia, both the CE and PF rats showed a statistically significant increase in signal intensity (22% ± 5% and 48% ± 6%, respectively, P < 0.05) relative to normoxia, while hypoxic challenge decreased the signal intensity (9% ± 4%, p>0.05 and 15% ± 3%, P < 0.05, respectively). The hypercapnic challenge, which causes vasodilation, resulted in a small increase in signal intensity in CE‐fed rats (5% ± 3%, P > 0.05) and a significant increase in the PF rats (15% ± 4%, P < 0.05), again consistent with expected changes in deoxyhemoglobin. With all three physiological challenges, the degree of change was less in CE rats compared to PF controls. An acute dose of ethanol that causes vasodilation also increased signal intensity, with no significant difference between the two groups. The signal intensity changes seen with fMRI were highly correlated with pulse oximeter readings (r2 = 0.95; P < 0.05). In conclusion, fMRI was shown to be a good noninvasive indicator of tissue deoxyhemoglobin changes in the liver. In addition, fMRI was able to detect subtle, early effects of CE administration (manifested as an impaired ability of the liver to respond adequately to oxygenation challenges), consistent with microvascular dysfunction. Magn Reson Med 50:976–983, 2003. © 2003 Wiley‐Liss, Inc.
Characterization and propagation of uncertainty in diffusion‐weighted MR imaging
Authors: Behrens T.E.J. , Woolrich M.W. , Jenkinson M. , Johansen‐Berg H. , Nunes R.G. , Clare S. , Matthews P.M. , Brady J.M. , Smith S.M. 
Published: October 2003

AbstractA fully probabilistic framework is presented for estimating local probability density functions on parameters of interest in a model of diffusion. This technique is applied to the estimation of parameters in the diffusion tensor model, and also to a simple partial volume model of diffusion. In both cases the parameters of interest include parameters defining local fiber direction. A technique is then presented for using these density functions to estimate global connectivity (i.e., the probability of the existence of a connection through the data field, between any two distant points), allowing for the quantification of belief in tractography results. This technique is then applied to the estimation of the cortical connectivity of the human thalamus. The resulting connectivity distributions correspond well with predictions from invasive tracer methods in nonhuman primate. Magn Reson Med 50:1077–1088, 2003. © 2003 Wiley‐Liss, Inc.
k‐t BLAST and k‐t SENSE: Dynamic MRI with high frame rate exploiting spatiotemporal correlations
Authors: Tsao Jeffrey , Boesiger Peter , Pruessmann Klaas P. 
Published: October 2003

AbstractDynamic images of natural objects exhibit significant correlations in k‐space and time. Thus, it is feasible to acquire only a reduced amount of data and recover the missing portion afterwards. This leads to an improved temporal resolution, or an improved spatial resolution for a given amount of acquisition. Based on this approach, two methods were developed to significantly improve the performance of dynamic imaging, named k‐t BLAST (Broad‐use Linear Acquisition Speed‐up Technique) and k‐t SENSE (SENSitivity Encoding) for use with a single or multiple receiver coils, respectively. Signal correlations were learned from a small set of training data and the missing data were recovered using all available information in a consistent and integral manner. The general theory of k‐t BLAST and k‐t SENSE is applicable to arbitrary k‐space trajectories, time‐varying coil sensitivities, and under‐ and overdetermined reconstruction problems. Examples from ungated cardiac imaging demonstrate a 4‐fold acceleration (voxel size 2.42 × 2.52 mm2, 38.4 fps) with either one or six receiver coils. k‐t BLAST and k‐t SENSE are applicable to many areas, especially those exhibiting quasiperiodic motion, such as imaging of the heart, the lungs, the abdomen, and the brain under periodic stimulation. Magn Reson Med 50:1031–1042, 2003. © 2003 Wiley‐Liss, Inc.
Regional atrophy in the brain of lissencephalic mouse lemur primates: Measurement by automatic histogram‐based segmentation of MR images
Authors: Dhenain Marc , Chenu Evelyne , Hisley Calvin K. , Aujard Fabienne , Volk Andreas 
Published: October 2003

AbstractAge‐related regional cerebral atrophy was evaluated in a small lissencephalic primate, model of cerebral aging. Twelve mouse lemurs (Microcebus murinus), ages 1.9–10.9 years (maximum life span: 12 years), were studied. 3D inversion‐recovery fast spin‐echo MR images (isotropic resolution = 234 μm) were recorded at 4.7 T with a surface coil actively decoupled from the transmitting birdcage probe. The surface coil‐related sensitivity gradient was corrected by normalization with images from an agar and NaCl phantom. An automatic statistical segmentation technique based on a classification‐maximization algorithm was tested on digital phantoms that mimicked the brain and applied to the 3D brain images. Segmented 3D maps that displayed gray matter, white matter, and cerebro‐spinal fluid (CSF) voxels were computed. The ventricles and peri‐encephalic spaces were categorized into 14 regions, defined on brain atlases on the basis of cytoarchitectural and anatomical criteria. The volume of CSF voxels belonging to each of these regions was calculated as an index of regional atrophy. Dilation of the mammillary fossa was an early event in the aging process. CSF accumulation within the occipital, parieto‐temporal, temporal, and frontal ventral peri‐encephalic spaces was particularly marked in the oldest animals that also displayed ophthalmologic alterations. Magn Reson Med 50:984–992, 2003. © 2003 Wiley‐Liss, Inc.
Proton HR‐MAS spectroscopy and quantitative pathologic analysis of MRI/3D‐MRSI‐targeted postsurgical prostate tissues
Authors: Swanson Mark G. , Vigneron Daniel B. , Tabatabai Z. Laura , Males Ryan G. , Schmitt Lars , Carroll Peter R. , James Joyce K. , Hurd Ralph E. , Kurhanewicz John 
Published: October 2003

AbstractProton high‐resolution magic angle spinning (1H HR‐MAS) NMR spectroscopy and quantitative histopathology were performed on the same 54 MRI/3D‐MRSI‐targeted postsurgical prostate tissue samples. Presurgical MRI/3D‐MRSI targeted healthy and malignant prostate tissues with an accuracy of 81%. Even in the presence of substantial tissue heterogeneity, distinct 1H HR‐MAS spectral patterns were observed for different benign tissue types and prostate cancer. Specifically, healthy glandular tissue was discriminated from prostate cancer based on significantly higher levels of citrate (P = 0.04) and polyamines (P = 0.01), and lower (P = 0.02) levels of the choline‐containing compounds choline, phosphocholine (PC), and glycerophosphocholine (GPC). Predominantly stromal tissue lacked both citrate and polyamines, but demonstrated significantly (P = 0.01) lower levels of choline compounds than cancer. In addition, taurine, myo‐inositol, and scyllo‐inositol were all higher in prostate cancer vs. healthy glandular and stromal tissues. Among cancer samples, larger increases in choline, and decreases in citrate and polyamines (P = 0.05) were observed with more aggressive cancers, and a MIB‐1 labeling index correlated (r = 0.62, P = 0.01) with elevated choline. The elucidation of spectral patterns associated with mixtures of different prostate tissue types and cancer grades, and the inclusion of new metabolic markers for prostate cancer may significantly improve the clinical interpretation of in vivo prostate MRSI data. Magn Reson Med 50:944–954, 2003. © 2003 Wiley‐Liss, Inc.
Radial alternating TE sequence for faster fat suppression
Authors: Flask Chris A. , Dale Brian , Lewin Jonathan S. , Duerk Jeffrey L. 
Published: October 2003

AbstractThis study describes a steady‐state sequence that uses a radial k‐space trajectory and alternating echo times (TEs) between even and odd k‐space views. The sequence generated a single data set that was used to reconstruct images with inherent fat suppression. This fat suppression results from the fat phase variation in alternate echoes giving rise to cancellation in the central portion of k‐space. This new fat‐suppression method provides inherent fat suppression in half the acquisition time relative to the radial two‐point Dixon method. The improvement in k‐space sampling efficiency is demonstrated in phantom and clinical images, and through measured point‐spread functions (PSFs). As a result, the radial alternating TE sequence offers improved temporal resolution over a radial version of the two‐point Dixon sequence by requiring fewer total projections to obtain the same effective resolution in water‐based tissues. Magn Reson Med 50:1095–1099, 2003. © 2003 Wiley‐Liss, Inc.
Development of a tissue‐equivalent MRI phantom using carrageenan gel
Authors: Yoshimura Koichi , Kato Hirokazu , Kuroda Masahiro , Yoshida Atsushi , Hanamoto Katsumi , Tanaka Akio , Tsunoda Masatoshi , Kanazawa Susumu , Shibuya Koichi , Kawasaki Shoji , Hiraki Yoshio 
Published: October 2003

AbstractA new tissue‐equivalent MRI phantom based on carrageenan gel was developed. Carrageenan gel is an ideal solidifying agent for making large, strong phantoms in a wide variety of shapes. GdCl3 was added as a T1 modifier and agarose as a T2 modifier. The relaxation times of a very large number of samples were estimated using 1.5‐T clinical MRI equipment. The developed phantom was found to have a T1 value of 202–1904 ms and a T2 value of 38–423 ms when the GdCl3 concentration was varied from 0–140 μmol/kg and the agarose concentration was varied from 0–1.6% in a carrageenan concentration that was fixed at 3%. The range of measured relaxation times covered those of all types of human tissue. Empirical formulas linking the relaxation time with the concentration of the modifier were established to enable the accurate and easy calculation of the modifier concentration needed to achieve the required relaxation times. This enables the creation of a phantom having an arbitrary combination of T1 and T2 values and which is capable of retaining its shape. Magn Reson Med 50:1011–1017, 2003. © 2003 Wiley‐Liss, Inc.
MR spectroscopy of muscle and brain in guanidinoacetate methyltransferase (GAMT)‐deficient mice: Validation of an animal model to study creatine deficiency
Authors: Renema W. Klaas Jan , Schmidt Andreas , van Asten Jack J.A. , Oerlemans Frank , Ullrich Kurt , Wieringa Bé , Isbrandt Dirk , Heerschap Arend 
Published: October 2003

AbstractAs a model for guanidinoacetate methyltransferase (GAMT) deficiency in humans, a gene knockout mouse model was generated. Here we report on several metabolic abnormalities in these mice, observed by in vivo and in vitro MR spectroscopy. In 1H MR spectra of brain and hindleg muscle a clearly reduced signal of creatine (Cr) was observed in GAMT‐deficient (GAMT–/–) animals. Analysis of the 1H MR spectra of GAMT–/– brain indicated little or no increase of a signal for guanidinoacetate (Gua). In proton MR spectra of muscle, a broad signal of low intensity was observed for Gua. However, substantial Gua accumulation in intact muscle tissue was unequivocally confirmed in high‐resolution magic angle spinning spectra, in which the Gua signal was resolved as one clear sharp singlet. In 31P MR analysis of brain and hindleg muscle a strongly reduced phosphocreatine (PCr) content was shown. In addition, a signal of phosphorylated Gua at 0.5 ppm upfield of PCr was observed, with much higher intensity in muscle than in brain. This signal decreased when ischemia was applied to the muscle and recovered after ischemia was released. Overall, the in vivo 31P and 1H MR spectroscopy of GAMT–/– mice is similar to that of human GAMT deficiency. This opens up new avenues for the fundamental study of tissue‐type dependence of creatine synthesis and transport and for diagnostic and therapeutic aspects of creatine deficiencies in humans. Magn Reson Med 50:936–943, 2003. © 2003 Wiley‐Liss, Inc.
Optimization of diffusion measurements using Cramer‐Rao lower bound theory and its application to articular cartilage
Authors: Brihuega‐Moreno Oscar , Heese Frank P. , Hall Laurance D. 
Published: October 2003

AbstractA novel approach to optimized diffusion measurements by minimizing the Cramer‐Rao lower bound (CRLB) with respect to the b‐values used for diffusion measurement was investigated. The applicability of the CRLB to these measurements is shown by the close agreement between the CRLB prediction and the actual precision obtained from experimental results. Where studies using a propagation‐of‐errors approach have restricted the optimization of the diffusion measurement to two b‐values and to specific diffusion coefficient values, the CRLB approach sets no bounds on the number of b‐values and is applicable to any system. The optimal number of b‐values depends on the ratio of the maximum and minimum diffusion coefficients in the sample (the Dratio) and on the number of acquisitions. For a Dratio above 6.8 the optimal number of b‐values increases to three; at a Dratio of 21.8 it increases to four. The optimized sampling schemes for ADC measurements in a variety of representative tissues found in the human body are given. For cartilage the optimal five‐point acquisition scheme requires one measurement at a b‐value of 0 and four at 1036 sec mm−2, whereas brain requires one at 0, three at 660, and one at 1987 sec mm−2. Magn Reson Med 50:1069–1076, 2003. © 2003 Wiley‐Liss, Inc.
Dixon techniques in spiral trajectories with off‐resonance correction: A new approach for fat signal suppression without spatial‐spectral RF pulses
Authors: Moriguchi Hisamoto , Lewin Jonathan S. , Duerk Jeffrey L. 
Published: October 2003

AbstractSpiral imaging has recently gained acceptance in MR applications requiring rapid data acquisition. One of the main disadvantages of spiral imaging, however, is blurring artifacts that result from off‐resonance effects. Spatial‐spectral (SPSP) pulses are commonly used to suppress those spins that are chemically shifted from water and lead to off‐resonance artifacts. However, SPSP pulses may produce nonuniform fat signal suppression or unwanted water signal suppression when applied in the presence of B0 field inhomogeneities. Dixon techniques have been developed as methods for water–fat signal decomposition in rectilinear sampling schemes since they can produce unequivocal water–fat signal decomposition even in the presence of B0 inhomogeneities. This article demonstrates that three‐point and two‐point Dixon techniques can be extended to conventional spiral and variable‐density spiral data acquisitions for unambiguous water–fat decomposition with off‐resonance blurring correction. In the spiral three‐point Dixon technique, water–fat signal decomposition and image deblurring are performed based on the frequency maps that are directly derived from the acquired images. In the spiral two‐point Dixon technique, several predetermined frequencies are tested to create a frequency map. The newly proposed techniques can achieve more effective and more uniform fat signal suppression when compared to the conventional spiral acquisition method with SPSP pulses. Magn Reson Med 50: 915–924, 2003. © 2003 Wiley‐Liss, Inc.
Flow effects in balanced steady state free precession imaging
Authors: Markl M. , Alley M.T. , Elkins C.J. , Pelc N.J. 
Published: October 2003

AbstractAn analysis of the effect of flow on 2D fully balanced steady state free precession (SSFP) imaging is presented. Transient and steady‐state SSFP signal intensities in the presence of steady and pulsatile flow were simulated using a matrix formalism based on the Bloch equations. Various through‐plane flow waveforms and rates were modeled numerically considering factors such as the excitation slice profile and both in‐ and out‐flow effects. Phantom measurements in an experimental setup that allowed the assessment of SSFP signal properties as a function of frequency offset and flow rate demonstrated that the computer simulations provided a suitable description of the effects of flow in SSFP imaging. A volunteer scan was performed to provide in vivo validations. For accurate modeling of SSFP signal intensities it is crucial to include effects such as imperfect slice profiles and, more importantly, “out‐of‐slice” contributions to the signal. Both simulations and experiments show that there can be considerably large—frequency offset dependent—signal contributions from flowing spins that have already left the imaging slice but still add to the SSFP signal. Although spins leaving the slice do not experience additional RF‐excitation, gradient activity is not confined to the region of excitations and the balanced nature of the SSFP imaging gradients allows “out‐of‐slice” transverse magnetization to contribute to the total SSFP signal, effectively by broadening the slice thickness for flowing spins. This results in a frequency dependence of in‐flow related signal enhancement and flow artifacts. Magn Reson Med 50:892–903, 2003. © 2003 Wiley‐Liss, Inc.
Degenerate mode birdcage volume coil for sensitivity‐encoded imaging
Authors: Lin Fa‐Hsuan , Kwong Kenneth K. , Huang Ing‐Jye , Belliveau John W. , Wald Lawrence L. 
Published: October 2003

AbstractA volume birdcage coil for accelerated image encoding with parallel acquisition methods such as SENSE is demonstrated. The coil is degenerately tuned with both the standard homogeneous mode and the first gradient mode of the birdcage coil resonant at the Larmor frequency. Conventional and antisymmetric coupling structures allow imaging from each of these modes simultaneously. The coil for SENSE‐type reconstruction with acceleration factors of up to 2‐fold is demonstrated. The spatial distribution of the added noise from the SENSE reconstruction (g‐factor map) due to geometrical arrangement of the two‐channel system is estimated. The spatially averaged g‐factors were found to be 1.21, 1.36, and 1.55 for 1.3, 1.6, and 2‐fold accelerations, respectively. The system was demonstrated in vivo using accelerated and nonaccelerated anatomical brain images at 1.5 T. The maximal 2‐fold acceleration in this dual‐mode degenerate birdcage coil offers the potential to extend SENSE‐type image reconstruction methods to applications demanding uniform whole brain coverage. Magn Reson Med 50:1107–1111, 2003. © 2003 Wiley‐Liss, Inc.
Inflow effect correction in fast gradient‐echo perfusion imaging
Authors: Ivancevic Marko K. , Zimine Ivan , Montet Xavier , Hyacinthe Jean‐Noel , Lazeyras François , Foxall David , Vallée Jean‐Paul 
Published: October 2003

AbstractThe purposes of this study were to assess the extent of the inflow effect on signal intensity (SI) for fast gradient‐recalled‐echo (GRE) sequences used to observe first‐pass perfusion, and to develop and validate a correction method for this effect. A phantom experiment with a flow apparatus was performed to determine SI as a function of Gd‐DTPA concentration for various velocities. Subsequently a flow‐sensitive calibration method was developed, and validated on bolus injections into an open‐circuit flow apparatus and in vivo. It is shown that calibration methods based on static phantoms are not appropriate for accurate signal‐to‐concentration conversion in images affected by high flow. The flow‐corrected calibration method presented here can be used to improve the accuracy and robustness of the arterial input function (AIF) determination for tissue perfusion quantification using MRI and contrast media. Magn Reson Med 50:885–891, 2003. © 2003 Wiley‐Liss, Inc.
Optimized gradient pulse for use with EPI employing active acoustic control
Authors: Chapman B. L. W. , Haywood B. , Mansfield P. 
Published: October 2003

AbstractThe concept of active acoustic control was recently introduced by Mansfield and Haywood (MAGMA 2000:10:147–151) to ameliorate the problem of acoustic noise from MRI, particularly that from high‐speed EPI. A 30 dB reduction in noise was previously achieved with the use of acoustic control operating at spot frequencies within a narrow band. In this work, a new acoustic gradient pulse is introduced that comprises an oscillating gradient of finite duration, incorporating a combination of frequencies within this band designed for use as the switched read gradient in echo‐planar imaging (EPI). Employing this pulse with active acoustic control results in a reduction of acoustic noise by 50 dB. Magn Reson Med 50:931–935, 2003. © 2003 Wiley‐Liss, Inc.
Predegenerated peripheral nerve graft with and without methylprednisolone administration after traumatic spinal cord injury in adult rats
Authors: Salgado‐Ceballos Hermelinda , Grijalva Israel , Guizar‐Sahagun Gabriel , Espitia Ana Laura , Martínez Angelina , Feria‐Velasco Alfredo 
Published: October 2003

AbstractTraumatic spinal cord injury (TSCI) produces paralysis by destruction of axons and demyelination of surviving fibers. Using methylprednisolone (MP) as neuroprotector and a predegenerated peripheral nerve (PPN) graft as regenerative strategy, 83 rats with TSCI were divided into non‐grafted, fresh peripheral nerve (FPN) and PPN grafted groups with and without MP administration. Myelination index (MI), number of axons, myelinated fibers, and axon collaterals were assessed 21 h, 7 days, 2, and 4 months after TSCI. Animals with PPN grafts showed more axons and myelinated fibers than animals with FPN grafts, while the latter showed the highest number of axon collaterals. When MP was used, collateral emission was decreased in all treated groups. However, PPN graft plus MP group had the best MI and highest number of axons and myelinated fibers. Combination of one neuroprotective with a regenerative strategy is a good therapeutic option, although new combinations should be further explored.
Neuroprotective effect of Alpinia oxyphylla extract against glutamate‐induced apoptosis in cultured mouse cortical neurons
Authors: Yu Xinyu , Ceballos Yongqui Wang , Zhao Hong , Xu Zhongqui 
Published: October 2003

AbstractGlutamate‐induced neuronal apoptosis plays an important role in neurodegenerative disorders. In the process of screening for naturally occurring substances with neuroprotective effects against glutamate exitotoxicity, we have discovered that the extract from Alpinia oxyphylla, a traditional Chinese medicinal herb, exhibited significant neuroprotective activity against glutamate exitotoxicity in cultured cortical neurons. The present study was designed to investigate the protective effect of Alpinia oxyphylla extract against glutamate‐induced neuronal apoptosis in primary cultured mouse cortical neurons. After exposure of the neurons to glutamate (30 μM), apoptotic cell death was observed as evidenced by alteration of neuronal morphology, DNA fragmentation on agarose gel and flow cytometric analysis. Co‐treatment of the neurons with Alpinia oxyphylla extract (80–240 μg/ml) in the presence of glutamate significantly elevated the cell viability, reduced the number of apoptotic cells and decreased the intensity of glutamate‐induced DNA fragmentation. The results suggest the neuroprotective potential of Alpinia oxyphylla against glutamate‐induced neuronal apoptosis.