bluuebunny/crossref_metadata_2025_split huggingface dataset:
T2 of articular cartilage in the presence of Gd‐DTPA2−
Authors: Nieminen Miika T. , Menezes Nina M. , Williams Ashley , Burstein Deborah 
Published: May 2004

AbstractT2 information and delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) are both used to characterize articular cartilage. They are currently obtained in separate studies because Gd‐DTPA2− (which is needed for dGEMRIC) affects the inherent T2 information. In this study, T2 was simulated and then measured at 8.45 T in 20 sections from two human osteochondral samples equilibrated with and without Gd‐DTPA2−. Both the simulations and data demonstrated that Gd‐DTPA2− provides a non‐negligible mechanism for relaxation, especially with higher (1 mM) equilibrating Gd‐DTPA2− concentrations, and in areas of tissue with high T2 (due to weak inherent T2 mechanisms) and high tissue Gd‐DTPA2− (due to a low glycosaminoglycan concentration). Nonetheless, T2‐weighted images of cartilage equilibrated in 1 mM Gd‐DTPA2− showed similar T2 contrast with and without Gd‐DTPA2−, demonstrating that the impact on T2 was not great enough to affect identification of T2 lesions. However, T2 maps of the same samples showed loss of conspicuity of T2 abnormalities. We back‐calculated inherent T2's (T2,bc) using a T2‐relaxivity value from a 20% protein phantom (r2 = 9.27 ± 0.09 mM−1s−1) and the Gd‐DTPA2− concentration calculated from T1,Gd. The back‐calculation restored the inherent T2 conspicuity, and a correlation between T2 and T2,bc of r = 0.934 (P < 0.0001) was found for 80 regions of interest (ROIs) in the sections. Back‐calculation of T2 is therefore a viable technique for obtaining T2 maps at high equilibrating Gd‐DTPA2− concentrations. With T2‐weighted images and/or low equilibrating Gd‐DTPA2− concentrations, it may be feasible to obtain both T2 and dGEMRIC information in the presence of Gd‐DTPA2− without such corrections. These conditions can be designed into ex vivo studies of cartilage. They appear to be applicable for clinical T2 studies, since pilot clinical data at 1.5 T from three volunteers demonstrated that calculated T2 maps are comparable before and after “double dose” Gd‐DTPA2− (as utilized in clinical dGEMRIC studies). Therefore, it may be possible to perform a comprehensive clinical examination of dGEMRIC, T2, and cartilage volume in one scanning session without T2 data correction. Magn Reson Med 51:1147–1152, 2004. © 2004 Wiley‐Liss, Inc.
Neuroprotective effects of an immunosuppressant agent on diffusion/perfusion mismatch in transient focal ischemia
Authors: Ebisu Toshihiko , Mori Yuuki , Katsuta Kiyotaka , Fujikawa Akihiko , Matsuoka Nobuya , Aoki Ichio , Umeda Masahiro , Naruse Shoji , Tanaka Chuzo 
Published: May 2004

AbstractThe immunosuppressant FK506 (tacrolimus) exerts potent neuroprotection following focal ischemia in animals; however, the separate effects of FK506 on the ischemic core and penumbra have not been reported. The ischemic penumbra is clinically defined as the difference between a large abnormal area on perfusion‐weighted imaging (PWI) and a smaller lesion on diffusion‐weighted imaging (DWI). The goal of this study was to determine the effect of FK506 on DWI/PWI match and mismatch areas in transient focal ischemia in rats. Twelve rats were subjected to 1 hr of transient middle cerebral artery (MCA) occlusion, and given an intravenous injection of a placebo (N = 6) or 1 mg/kg FK506 (N = 6) immediately before reperfusion. Magnetic resonance imaging (MRI) was performed during MCA occlusion, and 0.5, 1, and 24 hr after reperfusion. FK506 significantly protected the ischemic brain only in the mismatch cortex where the initial apparent diffusion coefficient (ADC) was normal and there was a mild reduction of cerebral blood flow (CBF). This is the first report to describe the protective effects of FK506 on ischemic penumbra, as measured by DWI/PWI mismatch. The findings provide direct evidence for the utility of DWI/PWI mismatch as a guideline for therapeutic intervention with FK506. Magn Reson Med 51:1173–1180, 2004. © 2004 Wiley‐Liss, Inc.
Acute cerebral ischemia in rats studied by Carr‐Purcell spin‐echo magnetic resonance imaging: Assessment of blood oxygenation level‐dependent and tissue effects on the transverse relaxation
Authors: Kavec Martin , Gröhn Olli H.J. , Kettunen Mikko I. , Silvennoinen M. Johanna , Garwood Michael , Kauppinen Risto A. 
Published: May 2004

AbstractAcute cerebral ischemia has been shown to be associated with an enhanced transverse relaxation rate in rat brain parenchyma, chiefly due to the blood oxygenation level‐dependent (BOLD) effect. In this study, Carr‐Purcell R2 (CP R2), acquired both with short and long time intervals between centers of adiabatic π‐pulses (τCP), was used to assess the contributions of BOLD and tissue effects to the transverse relaxation in two brain ischemia models of rat at 4.7 T. R1ρ and diffusion MR images were also acquired in the same animals. During the first minutes of global ischemia, the long τCP R2 in brain parenchyma increased, whereas the short τCP R2 was unchanged. Based on the simulations, and using constraints of intravascular BOLD effect on parenchymal R2, the former observation was ascribed to be due to susceptibility changes arising in the extravascular compartment. R1ρ declined almost immediately after the onset of focal cerebral ischemia, and further declined during the evolution of ischemic damage. Interestingly, short τCP CP R2 started to decline after some 20 min of focal ischemia and declined over a time course similar to that of R1ρ, indicating that it may be an MRI marker for irreversible tissue changes in cerebral ischemia. The present results show that CP R2 MRI can reveal both tissue‐ and blood‐derived contrast changes in acute cerebral ischemia. Magn Reson Med 51:1138–1146, 2004. © 2004 Wiley‐Liss, Inc.
In vitro release of vascular endothelial growth factor from gadolinium‐doped biodegradable microspheres
Authors: Faranesh Anthony Z. , Nastley Monet T. , Perez de la Cruz Cristina , Haller Michael F. , Laquerriere Patrice , Leong Kam W. , McVeigh Elliot R. 
Published: May 2004

AbstractA drug delivery vehicle was constructed that could be visualized noninvasively with MRI. The biodegradable polymer poly(DL‐lactic‐co‐glycolic acid) (PLGA) was used to fabricate microspheres containing vascular endothelial growth factor (VEGF) and the MRI contrast agent gadolinium diethylenetriamine pentaacetic acid (Gd‐DTPA). The microspheres were characterized in terms of size, drug and contrast agent encapsulation, and degradation rate. The PLGA microspheres had a mean diameter of 48 ± 18 μm. The gadolinium loading was 17 ± 3 μg/mg polymer and the VEGF loading was 163 ± 22 ng/mg polymer. Electron microscopy revealed that the Gd was dispersed throughout the microspheres and it was confirmed that the Gd loading was sufficient to visualize the microspheres under MRI. VEGF and Gd‐DTPA were released from the microspheres in vitro over a period of ∼6 weeks in three phases: a burst, followed by a slow steady‐state, then a rapid steady‐state. Biodegradable Gd‐doped microspheres can be effectively used to deliver drugs in a sustained manner, while being monitored noninvasively with MRI. Magn Reson Med 51:1265–1271, 2004. Published 2004 Wiley‐Liss, Inc.
Removal of EPI Nyquist ghost artifacts with two‐dimensional phase correction
Authors: Chen Nan‐kuei , Wyrwicz Alice M. 
Published: May 2004

AbstractOdd–even echo inconsistencies result in Nyquist ghost artifacts in the reconstructed EPI images. The ghost artifacts reduce the image signal‐to‐noise ratio and make it difficult to correctly interpret the EPI data. In this article a new 2D phase mapping protocol and a postprocessing algorithm are presented for an effective Nyquist ghost artifacts removal. After an appropriate k‐space data regrouping, a 2D map accurately encoding low‐ and high‐order phase errors is derived from two phase‐encoded reference scans, which were originally proposed by Hu and Le (Magn Reson Med 36:166–171;1996) for their 1D nonlinear correction method. The measured phase map can be used in the postprocessing algorithm developed to remove ghost artifacts in subsequent EPI experiments. Experimental results from phantom, animal, and human studies suggest that the new technique is more effective than previously reported methods and has a better tolerance to signal intensity differences between reference and actual EPI scans. The proposed method may potentially be applied to repeated EPI measurements without subject movements, such as functional MRI and diffusion coefficient mapping. Magn Reson Med 51:1247–1253, 2004. © 2004 Wiley‐Liss, Inc.
Prolonged T values in newborn versus adult brain: Implications for fMRI studies of newborns
Authors: Rivkin M.J. , Wolraich D. , Als H. , McAnulty G. , Butler S. , Conneman N. , Fischer C. , Vajapeyam S. , Robertson R.L. , Mulkern R.V. 
Published: May 2004

AbstractThe neonatal brain possesses higher water content, lower macromolecular concentration, and reduced synaptic density than is found in the brain of a 1‐year‐old child. Changes in MRI characteristics of brain such as relaxation times accompany rapid changes in brain during early postnatal development. It was hypothesized that T values found in newborns would be significantly higher than those found in 9‐month‐old children and adults as measured at 1.5 T. Spoiled gradient echo measurements of T within the brains of newborns, 9‐month‐olds, and adults confirmed this hypothesis. The results have implications with regard to functional MRI studies in newborns since, in general, BOLD signal optimization is achieved when echo times TE are set equal to the T values of the tissue of interest. Since significantly longer T values are found in newborns, it is suggested that the TE values employed for fMRI studies of newborns should be increased to maximize BOLD signal intensity changes and improve the overall reliability of fMRI results in newborns. Magn Reson Med 51:1287–1291, 2004. © 2004 Wiley‐Liss, Inc.
A fast integral approach for drag force calculation due to oscillatory slip stokes flows
Authors: Ding Jian , Ye Wenjing 
Published: May 2004

AbstractIn this paper, we describe an efficient numerical method for modelling oscillatory incompressible slip Stokes flows in three dimensions. The efficiency is achieved by employing an integral approach combined with an accelerated boundary‐element‐method (BEM) solver. First the integral representations for slip flows with two different slip models are formulated. The resulting integral equations are then solved using the BEM combined with the precorrected‐FFT accelerated technique. 3D numerical codes have been developed based on the method described above. These codes are then used to calculate the drag forces on oscillating objects immersed in an unbounded slip flow. Three objects are considered, namely a sphere, a pair of plates and a comb structure. The simulated drag forces on these objects obtained from the two slip models are compared. In the sphere case, the simulated results are also compared with the analytical solutions for both the steady‐state case and the no‐slip oscillatory case and are found to be in good agreement. In addition, qualitative comparison of the simulation results with the experimental results in the plate problem is also presented in this paper. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of transfer procedures in elastoplasticity based on the error in the constitutive equations: Theory and numerical illustration
Authors: Orlando A. , Perić D. 
Published: May 2004

AbstractThe aim of this work is to illustrate a methodology for the assessment of adaptive strategies for the solution of associative rate‐independent plasticity problems solved by employing the incremental displacement conforming finite element method. This is the first step towards a more rational definition of transfer operators in terms of the ensuing error. The motivating idea is the observation that change of data and/or finite element mesh from one time interval to the other can be both related to a discontinuity jump of the approximate solution across the time instant tn. Thus, reliable a posteriori estimates will have to depend not only on the time step and finite element mesh size but also on the value of the jump. A new error estimate based on the error in the constitutive equations is developed which allows characterization of the discontinuity jump. Copyright © 2004 John Wiley & Sons, Ltd.
Mesh‐free radial point interpolation method for the buckling analysis of Mindlin plates subjected to in‐plane point loads
Authors: Liew K. M. , Chen X. L. 
Published: May 2004

AbstractIn this paper, a mesh‐free approach is employed for buckling analysis of Mindlin plates that are subjected to in‐plane point loads. The radial point interpolation method (RPIM) is used to approximate displacements based on nodes. Variational forms of the system equations are established. Two‐step solution procedures are implemented. The non‐uniform pre‐stress distribution of plate is first obtained using the RPIM based on a two‐dimensional (2D) elastic plane stress problem. This predetermined non‐uniform pre‐stress distribution is then used to compute buckling loads of plate using the RPIM based on Mindlin's plate assumption. The RPIM can easily handle any number and location of nodes in the plate domain for a desired computational accuracy without major difficulties in solving the initial stresses and buckling loads. Numerical examples considered here include circular and rectangular Mindlin plates that are subjected to in‐plane uniform and point loads with different aspect ratios and boundary conditions. The present results are validated against the available analytical and numerical solutions. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and hydrolytic degradation of a random copolymer derived from 1,4‐dioxan‐2‐one and glycolide
Authors: Bhattarai Narayan , Jiang Wen Ying , Kim Hak Yong , Lee Douck Rae , Park Soo Jin 
Published: May 2004

AbstractNovel biodegradable copolymers, poly(1,4‐dioxan‐2‐one‐co‐glycolide) [P(DON‐co‐GA)] containing a high proportion of 1,4‐dioxan‐2‐one (DON), were synthesized by copolymerizations of DON and glycolide (GA) at 120 °C for 16 h using stannous octoate as catalyst. Chemical composition and microstructural variation of the resulting copolymer were investigated by 1H‐ and 13C NMR and thermal properties by differential scanning calorimetry (DSC). From the 13C NMR spectra, it was observed that, apart from the expected preponderance of DON sequences, the minor component, GA, was indeed distributed at various points along the copolymer chain rather than incorporated as distinct blocks, which is consistent with a random sequence distribution. This view also was supported by the DSC results, which showed that most copolymers were amorphous except for one with a relatively high fraction of DON. The conclusion that it was a random structure rather than a statistical copolymer is discussed, using the theories about the mechanism of this type of polymerization in current as a reference. P(DON‐co‐GA) films were prepared by casting the copolymer solution in hexafluoroisopropanol (HFIP) with two concentrations of the polymeric solution (10 and 25 wt %). The in vitro hydrolytic degradation behaviors of these films were studied in phosphate buffer solution (pH = 7.4) at 37 °C and characterized by DSC, scanning electron microscopy, weight loss, and change in inherent viscosity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2558–2566, 2004
CF: An X‐ray database to assess effect of aerosolized tobramycin
Authors: Slattery Dubhfeasa M. , Zurakowski David , Colin Andrew A. , Cleveland Robert H. 
Published: May 2004

AbstractThis paper assesses the effectiveness of aerosolized tobramycin (TOBI) on cystic fibrosis (CF) lung disease, using a radiologic tool. The published tool, the age‐based severity curve (ABS), is derived from Brasfield scoring of chest X‐rays (CXR). This study evaluates both the usefulness of the ABS as an assessment tool and the effectiveness of TOBI. Thirty‐eight patients were treated with TOBI. Twenty‐four treated with dornase alfa were excluded. Fourteen patients, aged 2 months to 22 years (mean, 17 months of TOBI treatment), comprised the study group. Radiographs were obtained over a mean of 7.8 years (SD = 6.5 years; range, 9 months–18 years). Two hundred and eighty‐two CXR of TOBI patients were analyzed following the ABS protocol. Rate of decline in radiologic status of the TOBI group and ABS were compared. Also, TOBI was assessed by comparing rate of decline before and after initiation of treatment. The TOBI group's radiologic assessment was compared to its rate of decline in pulmonary function studies and published population data. Rate of decline in ABS was 0.175 Brasfield points/year vs. 0.150 points/year in the TOBI group (P < 0.001). Before treatment, the TOBI group's rate of decline was 0.169 Brasfield points/year; after treatment, it was 0.150 points/year (P = 0.02). Forced vital capacity revealed a statistically significant slowing in rate of decline on TOBI. Although not statistically significant, rate of decline in forced expiratory volume at 1 sec showed a similar trend. The degree of slowing in decline is similar to that previously reported for pulmonary function studies. Pediatr Pulmonol. 2004; 38:23–30. © 2004 Wiley‐Liss, Inc.
Inspired gas temperature in ventilated neonates
Authors: Davies Mark William , Dunster Kimble Robert , Cartwright David William 
Published: May 2004

AbstractThe warming and humidification of inspired gases for ventilated neonates are routine. There are no data on the temperature of the gas at the airway opening in ventilated neonates. Is the inspired gas temperature at the airway opening, as expected and set on the humidifier, around 37°C? We aimed to measure temperature at the airway opening and compare this with the circuit temperature. This was an observational study in a neonatal intensive care unit. Twenty‐five mechanically ventilated infants were studied. All had humidifiers with chamber temperature set at 36°C and the circuit temperature set at 37°C. Two temperature probes were inserted and rested at the circuit‐exit and at the airway opening, and temperatures were measured for 2 min in each infant. At this time, the circuit temperature was also noted. The mean (SD) temperature at the airway opening in infants nursed in incubators was 34.9 (1.2)°C, compared with radiant warmers where the mean (SD) was 33.1 (0.5)°C. The mean (SD) difference in temperature from the circuit temperature probe to the airway opening was greater under radiant warmers, with a mean (SD) drop of 3.9 (0.6)°C compared with a mean (SD) drop of 2.0 (1.3)°C in the incubators. In conclusion, the temperature at the circuit temperature probe does not reflect the temperature at the airway opening. Inspired gas temperatures are lower than the expected 37°C with the normal circuits and usual humidifier settings. Pediatr Pulmonol. 2004; 38:50–54. © 2004 Wiley‐Liss, Inc.
Randomized, double‐blinded trial of low‐dose dexamethasone: II. Functional residual capacity and pulmonary outcome in very low birth weight infants at risk for bronchopulmonary dysplasia
Authors: McEvoy Cindy , Bowling Susan , Williamson Kathleen , McGaw Pam , Durand Manuel 
Published: May 2004

AbstractWe previously reported on a 7‐day course of dexamethasone starting at 0.5 mg/kg/day in intubated very low birth weight (VLBW) infants, 7–14 days of age, with increased dynamic pulmonary compliance and decreased bronchopulmonary dysplasia (BPD). The effect of low‐dose dexamethasone on functional residual capacity (FRC) in VLBW infants is unknown. The objective of this study was to compare the effect of two regimens of moderately early dexamethasone on FRC and passive respiratory compliance (Crs) in VLBW infants at risk for BPD. Sixty‐two intubated VLBW infants were randomized (double‐blinded) at 7–21 days of age; 29 patients (mean birth weight, 839 g) received “high” dose dexamethasone (0.5 mg/kg/day for 3 days, 0.25 mg/kg/day for 3 days, and 0.1 mg/kg/day on day 7, total dose of 2.35 mg/kg), and 33 infants (mean birth weight, 830 g) received “low‐dose” dexamethasone (0.2 mg/kg/day for 3 days and 0.1 mg/kg/day for 4 days, total dose of 1 mg/kg). FRC and Crs were measured with the nitrogen washout technique and single breath occlusion technique, before and on days 2, 5, and 7 of therapy. Clinical outcome and early neurodevelopmental follow‐up were evaluated. FRC significantly increased in the high‐dose (19.3 ml/kg at baseline to 34 ml/kg on day 7; P < 0.001) and low‐dose (18.1 ml/kg at baseline to 30.3 ml/kg on day 7; P < 0.001) dexamethasone groups when compared to baseline. There was a significant increase in Crs and a decrease in FiO2 within each group. The improvements in FRC and Crs were comparable between groups, and specific compliances (Crs/FRC) were not different. There were no significant differences in other clinical outcome parameters, including BPD and neurodevelopmental outcome. In conclusion, there are significant increases in FRC during a 7‐day course of moderately early dexamethasone in VLBW infants. The lower total dose (1 mg/kg) appears as effective as the higher total dose of dexamethasone (2.35 mg/kg) in increasing FRC. Comparable significant increases in Crs were observed in both groups of infants. Additional long‐term follow‐up is underway. Pediatr Pulmonol. 2004; 38:55–63. © 2004 Wiley‐Liss, Inc.
Dietary intake, physical activity, body mass index, and childhood asthma in the third national health and nutrition survey (NHANES III)
Authors: Romieu Isabelle , Mannino David M. , Redd Stephen C. , McGeehin Michael A. 
Published: May 2004

AbstractChildhood asthma may be affected by dietary changes and increased body mass related to a sedentary lifestyle, although the mechanisms are poorly understood. To test this hypothesis, we used data from the National Health and Nutrition Survey (NHANES III) from 1988–1994, including 7,904 children. We analyzed cross‐sectional information on body mass index (BMI = weight/height2), physical activity (hr/day viewing television), dietary intake (24‐hr recall), and vitamin C intake (60 mg/day). The probability of self‐reported asthma or wheezing relating to risk factors was calculated by logistic regression. After controlling for dietary intake, physical activity, and sociodemographic variables, asthma risk was three times higher for children aged 6–16 years in the highest percentiles of BMI (>95th percentile) when compared to children in percentiles 25–49 (OR = 3.44; 95% CI, 1.49–7.96). No increase was observed in children aged 2–5 years. Low vitamin C intake was marginally related to self‐reported current wheezing in children aged 6–16 years. Our results show that increased BMI may influence asthma prevalence in children, but further investigation is needed. Pediatr Pulmonol. 2004; 38:31–42. © 2004 Wiley‐Liss, Inc.