bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolite and diffusion changes in the rat brain after Leksell Gamma Knife irradiation
Authors: Herynek Vít , Burian Martin , Jirák Daniel , Liščák Roman , Náměstková Kateřina , Hájek Milan , Syková Eva 
Published: July 2004

AbstractOur study describes the time course of necrotic damage to the rat brain resulting from Leksell Gamma Knife (LGK) irradiation at a dose that was previously considered to be subnecrotic. A lesion induced in the rat hippocampus by 35 Gy irradiation was monitored by MRI, MRS, and DW‐MRI for 16 months. T2‐weighted images revealed a large hyperintense area with an increased apparent diffusion coefficient of water (ADCw), which occurred 8 months after irradiation, accompanied by metabolic changes (increase of lactate (Lac) and choline (Cho), and decrease of creatine (Cr) and N‐acetyl aspartate (NAA), as determined by MRS) that indicated an edema. In two animals, the hyperintensity persisted and a postnecrotic cavity connected to enlarged lateral ventricles developed. In the rest of the animals, the hyperintensity started to decrease 9 months post‐irradiation (PI), revealing hypointense areas with a decreased ADCw. Histology confirmed the MRI data, showing either scar formation or the development of a postnecrotic cavity. Magn Reson Med 52:397–402, 2004. © 2004 Wiley‐Liss, Inc.
Factors affecting the accuracy of pressure measurements in vascular stenoses from phase‐contrast MRI
Authors: Nasiraei‐Moghaddam Abbas , Behrens Geoffrey , Fatouraee Nasser , Agarwal Ramesh , Choi Eric T. , Amini Amir A. 
Published: July 2004

AbstractIn this work the effects of noise, resolution, and velocity (flow) on the measurement of intravascular pressure from phase‐contrast (PC) MRI are discussed. To elucidate these effects, we employed an axisymmetric geometry that enabled us to calculate pressures in <2 min on a Sun Ultra SPARC 10 workstation. To determine the effects of vascular stenoses, we fabricated several stenotic phantom geometries (with 50%, 75%, and 90% area stenoses), and performed both MRI and computational fluid dynamics (CFD) simulations for various flow rates for these phantom geometries. Noise with Gaussian statistics was added to the velocity field obtained from the CFD simulations. The pressure maps obtained directly from CFD simulations for our phantom geometries were compared with pressure maps derived by our algorithm when 1) the input was noise‐corrupted velocity data from CFD, and 2) the input was PC‐MRI data collected from the phantoms. The quantitative effects of noise, resolution, and flow rate on the accuracy of pressure measurements were determined. We found that for flow rates below the Reynolds number for turbulent flow, resolution is a more significant determinant of accuracy than SNR. Furthermore, if other parameters remain constant, increased flow rates may result in decreased accuracy. Magn Reson Med 52:300–309, 2004. © 2004 Wiley‐Liss, Inc.
Contribution of oxygenation to BOLD contrast in exercising muscle
Authors: Jordan Bénédicte F. , Kimpalou José Zéfu , Beghein Nelson , Dessy Chantal , Feron Olivier , Gallez Bernard 
Published: July 2004

AbstractThe potential physiological and therapeutic applications of functional MRI (fMRI) in skeletal muscle will depend on our ability to identify factors that may contribute to fluctuations in the BOLD signal. Until now, interpretations of signal changes in fMRI studies of muscle have mostly relied on the increase in muscle T2 associated with osmotically driven fluid shifts. However, recent studies have documented increases in BOLD signal intensity (SI) after single contractions, coinciding with increases in muscle hemoglobin saturation. In this study, the factors that contribute to variations in the intensity of the BOLD signal in exercising muscle are further addressed. For this purpose, BOLD imaging was performed during and after a moderate electrical stimulation was applied to the sciatic nerve in mice. In addition, oxygen pressure (pO2), blood flow, and skeletal muscle T2 (fast and slow components: T2 and T, respectively) were monitored. A comparison between mice lacking eNOS (eNOS−/− mice) and their wild‐type (WT) littermates was performed. In WT mice, the BOLD SI, as well as muscle oxygenation and T, were significantly increased for a prolonged time in response to this moderate exercise protocol. Blood flow immediately dropped after the electrical stimulation was stopped. In eNOS−/− mice, the high BOLD SI did not persist after the exercise protocol ended. This finding correlates well with the evolution of muscle oxygenation, which progressively decreases after stimulation in eNOS−/− mice. However, T remained high for a prolonged time after stimulation. We therefore concluded that the maintenance of BOLD SI in moderately exercising skeletal muscle depends mainly on changes in pO2, rather than on blood flow or T2 effects. Magn Reson Med 52:391–396, 2004. © 2004 Wiley‐Liss, Inc.
Coherence‐induced artifacts in large‐flip‐angle steady‐state spin‐echo imaging
Authors: Vasilic Branimir , Song Hee Kwon , Wehrli Felix W. 
Published: July 2004

AbstractHigh‐resolution imaging of trabecular bone aimed at analyzing the bone's microarchitecture is preferably performed with spin‐echo‐type pulse sequences. Unlike gradient echoes, spin‐echoes are immune to artifactual broadening of trabeculae caused by local static field gradients near the bone–bone marrow interface and signal loss from chemical shift dephasing at k‐space center. However, the previously practiced 3D fast large‐angle spin‐echo (FLASE) pulse sequence was found to be prone to a low‐frequency modulation artifact in both the readout and slice direction. The artifact is caused by deviations in the effective flip angle of the nonselective 180° pulse, which converts a fraction of the phase‐encoded transverse magnetization to longitudinal magnetization. The latter recurs as transverse magnetization in the subsequent pulse sequence cycle forming a spurious stimulated echo. The objective of this work was to perform a k‐space analysis of this steady‐state artifact and propose two modifications of the original 3D FLASE that effectively remove it. The results of the simulations were in exact agreement with the experiments and the proposed remedy was found to eliminate the artifact. Magn Reson Med 52:346–353, 2004. © 2004 Wiley‐Liss, Inc.
Multiprocessor scheduling implementation of the simultaneous multiple volume (SMV) navigator method
Authors: Kolmogorov Vladimir , Nguyen Thanh D. , Nuval Anthony , Spincemaille Pascal , Prince Martin R. , Zabih Ramin , Wang Yi 
Published: July 2004

AbstractThe simultaneous multiple volume (SMV) approach in navigator‐gated MRI allows the use of the whole motion range or the entire scan time for the reconstruction of final images by simultaneously acquiring different image volumes at different motion states. The motion tolerance range for each volume is kept small, thus SMV substantially increases the scan efficiency of navigator methods while maintaining the effectiveness of motion suppression. This article reports a general implementation of the SMV approach using a multiprocessor scheduling algorithm. Each motion state is regarded as a processor and each volume is regarded as a job. An efficient scheduling that completes all jobs in minimal time is maintained even when the motion pattern changes. Initial experiments demonstrated that SMV significantly increased the scan efficiency of navigator‐gated MRI. Magn Reson Med 52:362–367, 2004. © 2004 Wiley‐Liss, Inc.
Fast three‐dimensional k‐space trajectory design using missile guidance ideas
Authors: Mir Roberto , Guesalaga Andres , Spiniak Juan , Guarini Marcelo , Irarrazaval Pablo 
Published: July 2004

AbstractThree‐dimensional (3D) k‐space trajectories are needed to acquire volumetric images in MRI. While scan time is determined by the trajectory efficiency, image quality and distortions depend on the shape of the trajectories. There are several 3D trajectory strategies for sampling the k‐space using rectilinear or curve schemes. Since there is no evidence about their optimality in terms of image quality and acquisition time, a new design method based on missile guidance ideas is explored. Since air‐to‐air missile guidance shares similar goals and constraints with the problem of k‐space trajectory design, a control approach for missiles is used to design a 3D trajectory. The k‐space is divided into small cubes, and each one is treated as a target to be sampled. The main goal is to cover the entire space as quickly and efficiently as possible, with good performance under different conditions. This novel design method is compared to other trajectories using simulated and real data. As an example, a trajectory that requires 0.11 times the number of shots needed by the cylindrical 3DFT acquisition was designed. This trajectory requires more shots (1.66 times) than the stack of spirals, but behaves better under nonideal conditions, such as off‐resonance and motion. Magn Reson Med 52:329–336, 2004. © 2004 Wiley‐Liss, Inc.
Multiple spin‐echo spectroscopic imaging for rapid quantitative assessment of N‐acetylaspartate and lactate in acute stroke
Authors: Stengel Astrid , Neumann‐Haefelin Tobias , Singer Oliver C. , Neumann‐Haefelin Claudia , Zanella Friedhelm E. , Lanfermann Heinrich , Pilatus Ulrich 
Published: July 2004

AbstractMonitoring the signal levels of lactate (Lac) and N‐acetylaspartate (NAA) by chemical shift imaging can provide additional knowledge about tissue damage in acute stroke. Despite the need for this metabolic information, spectroscopic imaging (SI) has not been used routinely for acute stroke patients, mainly due to the long acquisition time required. The presented data demonstrate that the application of a fast multiple spin‐echo (MSE) SI sequence can reduce the measurement time to 6 min (four spin echoes per echo train, 32 × 32 matrix). Quantification of Lac and NAA in terms of absolute concentrations (i.e., mmol/l) can be achieved by means of the phantom replacement approach, with correction terms for the longitudinal and transversal relaxation adapted to the multiple spin‐echo sequence. In this pilot study of 10 stroke patients (symptom onset < 24 hr), metabolite concentrations obtained from MSE‐SI add important information regarding tissue viability that is not provided by other sequences (e.g., diffusion‐weighted imaging (DWI) and perfusion‐weighted imaging (PWI)). Metabolic changes extended beyond the borders of the apparent diffusion coefficient (ADC) lesion in nine of the 10 patients, showing a rise in Lac concentrations up to 18 mmol/l, while NAA levels sometimes dropped below the detection level. Considerable differences among the patients in terms of the Lac concentrations and the size of the SI‐ADC mismatch were observed. Magn Reson Med 52:228–238, 2004. © 2004 Wiley‐Liss, Inc.
Off‐resonance effects in the transient response of SSFP sequences
Authors: Ganter Carl 
Published: July 2004

AbstractA previously developed eigenvector formalism is adapted to off‐resonance in the transient response of quasiperiodic steady‐state free precession (SSFP) sequences, including TrueFISP as a special case. The effective relaxation rates for essentially parallel and perpendicular deviations from the steady state are determined analytically in leading order perturbation theory. The latter are a known cause of oscillatory artifacts and therefore constitute the main target of a variety of preparation techniques. In addition, the former also play a dominating role in applications such as inversion recovery (IR) TrueFISP, which intentionally measure far away from the equilibrium. For both components, the approach toward equilibrium turns out to depend sensitively on field inhomogeneities, especially for smaller ratios of T2/T1. For the perpendicular deviations, the calculations show that—except very close to banding artifacts, where the steady‐state signal is almost zero—field inhomogeneities additionally increase their effective relaxation rate almost as much as in the free induction decay (FID). The analytical results are tested against numerical simulation and MR measurements. Magn Reson Med 52:368–375, 2004. © 2004 Wiley‐Liss, Inc.
Electrodynamics and ultimate SNR in parallel MR imaging
Authors: Wiesinger Florian , Boesiger Peter , Pruessmann Klaas P. 
Published: July 2004

AbstractThe purpose of this article is to elucidate inherent limitations to the performance of parallel MRI. The study focuses on the ultimate signal‐to‐noise ratio (SNR), which refers to the maximum SNR permitted by the electrodynamics of the signal detection process. Using a spherical model object, it is shown that the behavior of the ultimate SNR imposes distinct limits on the acceleration rate in parallel imaging. For low and moderate acceleration, the ultimate SNR performance is nearly optimal, with geometry factors close to 1. However, for high reduction factors beyond a critical value, the ultimate performance deteriorates rapidly, corresponding to exponential growth of the geometry factor. The transition from optimal to deteriorating performance depends on the electrodynamic characteristics of the detected RF fields. In the near‐field regime, i.e., for low B0 and small object size, the critical reduction factor is constant and approximately equal to four for 1D acceleration in the sphere. In the far‐field wave regime the critical reduction factor is larger and increases both with B0 and object size. Therefore, it is concluded that parallel techniques hold particular promise for human MR imaging at very high field. Magn Reson Med 52:376–390, 2004. © 2004 Wiley‐Liss, Inc.
The Brazilian experience with a photovoltaic powered reverse osmosis plant
Authors: de Carvalho Paulo Cesar Marques , Riffel Douglas Bressan , Freire Cristiano , Montenegro Francisco Fabio Damasceno 
Published: July 2004

AbstractThis article describes a system that combines the technologies of reverse osmosis and photovoltaics to realize a pioneer project for drinking water supply to a rural community in semi‐arid Brazil (latitude 3°44′S), with a local yearly average temperature of 28°C and a yearly solar potential of about 2000 kW h m−2. Two strategies are investigated: first the PV‐RO (photovoltaic powered reverse osmosis) plant is equipped with a DC motor; and second, a three‐phase induction motor is used. Through the analysis of the stored data the second option is chosen as the better alternative. This strategy has a specific electrical consumption (energy required to produce 1 m3 drinking water) of 3·03 kW h m−3, a recovery ratio of 27% (relation between drinking water product flow and brackish water input flow) and a drinking water cost of US$ 12·76 per m3. Copyright © 2004 John Wiley & Sons, Ltd.
Light‐modulated lock‐in thermography for photosensitivepn‐structures and solar cells
Authors: Kaes M. , Seren S. , Pernau T. , Hahn G. 
Published: July 2004

AbstractLock‐in thermography (LIT) is a well‐established tool for defect analysis of solar cells, but so far has been restricted to the measurement of metallized samples. The new light‐modulated lock‐in thermography (LimoLIT) described in this paper overcomes this restriction by generating the voltage modulation needed for detection from photovoltaic conversion of modulated light. Thus wafers can be measured during all stages of fabrication, apn‐junction provided. The contactless LimoLIT method shows a stronger measurement signal and invokes a current flow close to illuminated operating conditions of solar cells, whereas conventional LIT is only comparable to a darkI–Vmeasurement. Copyright © 2004 John Wiley & Sons, Ltd.
Solar cell efficiency tables (version 24)
Authors: Green Martin A. , Emery Keith , King David L. , Igari Sanekazu , Warta Wilhelm 
Published: July 2004

AbstractConsolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since January 2004 are reviewed. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of the humoral immune response to immunoselected phage‐displayed peptides by a microarray‐based method
Authors: Cekaite Lina , Haug Ola , Myklebost Ola , Aldrin Magne , Østenstad Bjørn , Holden Marit , Frigessi Arnoldo , Hovig Eivind , Sioud Mouldy 
Published: July 2004

AbstractWe describe a novel approach for high‐throughput analysis of the immune response in cancer patients using phage‐based microarray technology. The recombinant phages used for fabricating phage arrays were initially selected via the use of random peptide phage libraries and breast cancer patient serum antibodies. The peptides displayed by the phages retained their ability to be recognized by serum antibodies after immobilization. The recombinant phage microarrays were screened against either breast cancer or healthy donor serum antibodies. A model‐based statistical method is proposed to estimate significant differences in serum antibody reactivity between patients and normals. A significant tumor effect was found with most of the selected phage‐displayed peptides, suggesting that recombinant phage microarrays can serve as a tool in monitoring humoral responses towards phage‐displayed peptides.
Proteomic analysis of differential protein expression in neuropathic pain and electroacupuncture treatment models
Authors: Sung Ho Joong , Kim Yoon Suk , Kim In Sik , Jang Sung‐Wuk , Kim Yoon Rim , Na Doe Sun , Han Ki Hoon , Hwang Byung Gil , Park Dong Suk , Ko Jesang 
Published: July 2004

AbstractAcupuncture has long been used for pain relief. Although recent studies have shown that acupuncture can reduce neuropathic pain, the mechanism of this effect is not clear and little information is available regarding proteins that are involved in the development of neuropathic pain and the effects of acupuncture. We have developed an animal model for neuropathic pain using young adult male Sprague‐Dawley rats. The model was confirmed by behavioral tests. Electroacupuncture (EA) treatment was applied to Zusanli (ST36) of neuropathic pain model to examine the analgesic effect of EA. The protein expression profile of the hypothalamus in both neuropathic pain and EA treatment models was analyzed using two‐dimensional electrophoresis‐based proteomics. We detected thirty‐six proteins that were differentially expressed in the neuropathic pain model compared with normal rats and that restored to normal expression levels after EA treatment. Twenty‐one of these proteins were identified in the MS‐FiT database and are involved in a number of biological processes, including inflammation, enzyme metabolism and signal transduction. Potential applications of our results include the identification and characterization of signaling pathways involved in EA treatment and further exploration of the role of selected identified proteins in the animal model.
Surface‐enhanced laser desorption/ionization‐time of flight‐mass spectrometry approach to biomarker discovery in blue mussels (Mytilus edulis) exposed to polyaromatic hydrocarbons and heavy metals under field conditions
Authors: Knigge Thomas , Monsinjon Tiphaine , Andersen Odd‐Ketil 
Published: July 2004

AbstractProteomics provide potential in the discovery of new sensitive biomarkers for environmental pollution. To evaluate this potential, we have utilized ProteinChip® technology to analyze the proteomic profile of blue mussels (Mytilus edulis) from polluted marine habitats surrounding the island of Karmøy, Norway. Two different types of contamination, heavy metals and polyaromatic hydrocarbons (PAHs), were compared to a clean reference site. Differentially expressed proteins/peptides were found, which showed a specific induction or a general suppression associated with the field site of origin. By combining sets of protein markers in a tree‐building algorithm, we were able to correctly classify samples from these sites with an accuracy of 90%.
Two‐dimensional electrophoresis for the isolation of integral membrane proteins and mass spectrometric identification
Authors: Rais Isam , Karas Michael , Schägger Hermann 
Published: July 2004

AbstractAcrylamide concentration, urea content, and the trailing ion used for sodium dodecyl sulfate (SDS)‐gels modify electrophoretic protein mobilities in a protein‐dependent way. Varying these parameters we coupled two SDS‐gels to a two‐dimensional (2‐D) electrophoresis system. Protein spots in 2‐D gels are dispersed around a diagonal. Hydrophobic proteins are well separated from water‐soluble proteins which is the essential advantage of the novel technique. Mass spectrometric identification of previously unaccessible hydrophobic proteins is now possible.
Initiation of free‐radical polymerization by peroxypivalates studied by electrospray ionization mass spectrometry
Authors: Buback Michael , Frauendorf Holm , Vana Philipp 
Published: July 2004

AbstractInitiation by tert‐butyl peroxypivalate (TBPP), tert‐amyl peroxypivalate (TAPP), 1,1,3,3‐tetramethylbutyl peroxypivalate (TMBPP), or 1,1,2,2‐tetramethylpropyl peroxypivalate (TMPPP) of radical polymerization of methyl methacrylate in toluene solution at 90 °C was studied via polymer end‐group analysis using electrospray ionization mass spectrometry (ESI‐MS). Conclusive peak assignments allowed for measuring the type and concentration of the fragments that actually initiate macromolecular growth after thermal decomposition of these peroxypivalates. It was found that the pivaloyloxy radical moiety undergoes instantaneous decarboxylation to yield an initiating tert‐butyl radical. The alkoxy radical moiety, on the other hand, may generate, via β‐scission reaction, different types of carbon‐centered radicals (together with a ketone) or may undergo a 1,5‐H‐shift reaction, by which reaction an oxygen‐centered radical is transformed into a carbon‐centered hydroxy radical. This hydrogen shift reaction was found in case of TMBPP. Surprisingly, no evidence for initiating alkoxy radicals could be found, not even in case of initiation by TBPP, where the intermediate tert‐butoxy radical undergoes a rapid chain‐transfer reaction with the solvent toluene. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4266–4275, 2004
Obesity and the risk of prostate cancer
Authors: Porter Michael P. , Stanford Janet L. 
Published: July 2004

AbstractBackgroundProstate cancer and obesity are common diseases among men in the United States. A link between obesity and prostate cancer risk has potential implications in understanding prostate cancer genesis and screening strategies.MethodsWe conducted a population‐based case‐control study examining the relationship between body mass index (BMI) and prostate cancer risk. Incident cases of prostate cancer were identified in King County, Washington, using the Surveillance, Epidemiology, and End Results (SEER) cancer registry. Interviews were completed with 753 men ages 40–64 that were diagnosed with prostate cancer between 1993 and 1996. Interviews were also completed with 703 age‐matched controls identified from the same population through random digit dialing. Logistic regression was performed to generate odds ratios and 95% confidence intervals while controlling for age, race, education, smoking, family history, prostate cancer screening, dietary fat, and caloric intake.ResultsBMI was inversely related to prostate cancer risk (P for trend = 0.04). Men with a BMI > 29 kg/m2 had the lowest risk of prostate cancer (odds ratio = 0.77; 95% confidence interval = 0.56, 1.06). Weight was also inversely associated with prostate cancer risk (P for trend = 0.03), however, height was not.ConclusionsThe results of this study support the hypothesis that obesity is inversely associated with prostate cancer risk in middle‐aged men. © 2004 Wiley‐Liss, Inc.