bluuebunny/crossref_metadata_2025_split huggingface dataset:
Velocity‐driven adiabatic fast passage for arterial spin labeling: Results from a computer model
Authors: Utting Jane F. , Thomas David L. , Gadian David G. , Ordidge Roger J. 
Published: January 2003

AbstractVelocity‐driven adiabatic fast passage (AFP) is commonly employed for perfusion imaging by continuous arterial spin labeling (CASL). The degree of inversion of protons in blood determines the sensitivity of CASL to perfusion. For this study, a computer model of the modified Bloch equations was developed to establish the optimum conditions for velocity‐driven AFP. Natural variations in blood velocity over the course of the cardiac cycle were found to result in significant variations in the degree of inversion. However, the mean degree of inversion was similar to that for blood moving at a constant velocity, equal to the time‐averaged mean, at peak velocities and heart rates within normal ranges. A train of RF pulses instead of a continuous RF pulse for labeling was found to result in a highly nonlinear dependence of the degree of inversion on RF duty cycle. This may have serious implications for the quantification of perfusion. Magn Reson Med 49:398–401, 2003. © 2003 Wiley‐Liss, Inc.
Characterization of effects of mean arterial blood pressure induced by cocaine and cocaine methiodide on BOLD signals in rat brain
Authors: Luo Feng , Wu Gaohong , Li Zhu , Li Shi‐Jiang 
Published: January 2003

AbstractA total of 45 male Sprague‐Dawley rats were employed to determine whether cocaine or cocaine methiodide (CM) administration can induce a significant increase in mean arterial blood pressure (MABP) in rats, and whether such an increase in MABP can produce a global increase in blood oxygenation level‐dependent (BOLD) contrast in the rat brain detectable by functional magnetic resonance imaging (fMRI). Cocaine methiodide is a quaternary derivative of cocaine that shares the same cardiovascular effects of cocaine, but does not penetrate the blood‐brain barrier (BBB). Experimental results demonstrated that both CM (with doses of 2.5 and 7.5 mg/kg) and cocaine (with doses of 1.25 and 5.0 mg/kg) can induce a significant MABP change (30–80%). It was found that CM can only produce scattered, weak, and transient BOLD signals in a few voxels of the rat brain, and that these MABP‐induced BOLD signals are not dose‐dependent. In contrast, the administration of cocaine induced dose‐dependent biphasic BOLD signals that were consistent with pharmacologically‐induced cerebral vascular constriction and neuronal activity in the mesolimbic systems of the rat brain. The potential confounding factor of the MABP changes had little effect on the interpretation of drug‐induced BOLD signal changes. These results confirm that the BOLD‐weighted fMRI method can be extended to map drug‐induced neuronal activity. Magn Reson Med 49:264–270, 2003. © 2003 Wiley‐Liss, Inc.
Metabolic profiles of human brain tumors using quantitative in vivo 1H magnetic resonance spectroscopy
Authors: Howe F.A. , Barton S.J. , Cudlip S.A. , Stubbs M. , Saunders D.E. , Murphy M. , Wilkins P. , Opstad K.S. , Doyle V.L. , McLean M.A. , Bell B.A. , Griffiths J.R. 
Published: January 2003

AbstractProton spectroscopy can noninvasively provide useful information on brain tumor type and grade. Short‐ (30 ms) and long‐ (136 ms) echo time (TE) 1H spectra were acquired from normal white matter (NWM), meningiomas, grade II astrocytomas, anaplastic astrocytomas, glioblastomas, and metastases. Very low myo‐Inositol ([mI]) and creatine ([Cr]) were characteristic of meningiomas, and high [mI] characteristic of grade II astrocytomas. Tumor choline ([Cho]) was greater than NWM and increased with grade for grade II and anaplastic astrocytomas, but was highly variable for glioblastomas. Higher [Cho] and [Cr] correlated with low lipid and lactate (P < 0.05), indicating a dilution of metabolite concentrations due to necrosis in high‐grade tumors. Metabolite peak area ratios showed no correlation with lipids and mI/Cho (at TE = 30 ms), and Cr/Cho (at TE = 136 ms) best correlated with tumor grade. The quantified lipid, macromolecule, and lactate levels increased with grade of tumor, consistent with progression from hypoxia to necrosis. Quantification of lipids and macromolecules at short TE provided a good marker for tumor grade, and a scatter plot of the sum of alanine, lactate, and δ1.3 lipid signals vs. mI/Cho provided a simple way to separate most tumors by type and grade. Magn Reson Med 49:223–232, 2003. © 2003 Wiley‐Liss, Inc.
Quantitative HRMAS proton total correlation spectroscopy applied to cultured melanoma cells treated by chloroethyl nitrosourea: Demonstration of phospholipid metabolism alterations
Authors: Morvan Daniel , Demidem Aicha , Papon Janine , Madelmont Jean Claude 
Published: January 2003

AbstractRecent NMR spectroscopy developments, such as high‐resolution magic angle spinning (HRMAS) probes and correlation‐enhanced 2D sequences, now allow improved investigations of phospholipid (Plp) metabolism. Using these modalities we previously demonstrated that a mouse‐bearing melanoma tumor responded to chloroethyl nitrosourea (CENU) treatment in vivo by altering its Plp metabolism. The aims of the present study were to investigate whether HRMAS proton total correlation spectroscopy (TOCSY) could be used as a quantitative technique to probe Plp metabolism, and to determine the Plp metabolism response of cultured B16 melanoma cells to CENU treatment in vitro. The exploited TOCSY signals of Plp derivatives arose from scalar coupling among the protons of neighbor methylene groups within base headgroups (choline and ethanolamine). For strongly expressed Plp derivatives, TOCSY signals were compared to saturation recovery signals and demonstrated a linear relationship. HRMAS proton TOCSY was thus used to provide concentrations of Plp derivatives during long‐term follow‐up of CENU‐treated cell cultures. Strong Plp metabolism alteration was observed in treated cultured cells in vitro involving a down‐regulation of phosphocholine, and a dramatic and irreversible increase of phosphoethanolamine. These findings are discussed in relation to previous in vivo data, and to Plp metabolism enzymatic involvement. Magn Reson Med 49:241–248, 2003. © 2003 Wiley‐Liss, Inc.
Rapid measurement of time‐averaged blood flow using ungated spiral phase‐contrast
Authors: Park Jong B. , Olcott Eric W. , Nishimura Dwight G. 
Published: January 2003

AbstractA novel ungated spiral phase‐contrast (USPC) imaging method was developed for rapid measurement of time‐averaged blood‐flow rates in the presence of pulsatility. The spatial point‐spread function was analyzed to provide an intuitive understanding of how spiral trajectories, which sample the k‐space origin at every excitation, can mitigate the effects of pulsatility. Pulsatile flow phantom experiments were performed to validate the accuracy and repeatability of the USPC method. The measurement of flow in the renal and femoral arteries of normal volunteers were also performed. The phantom results (error ≤ +9%, SDphantom ≤ 2%, time‐averaged pulsatile‐flow rates = 3–15 ml/s) and in vivo results (SDrenal ≤ 8%, SDfemoral ≤ 14%) demonstrate the potential of the USPC method for rapidly and repeatedly measuring accurate time‐averaged blood flow even in relatively small arteries and in the presence of strong pulsatility. Magn Reson Med 49:322–328, 2003. © 2003 Wiley‐Liss, Inc.
Pulsed arterial spin labeling using TurboFLASH with suppression of intravascular signal
Authors: Pell Gaby S. , Lewis David P. , Branch Craig A. 
Published: January 2003

AbstractAccurate quantification of perfusion with the ADC techniques requires the suppression of the majority of the intravascular signal. This is normally achieved with the use of diffusion gradients. The TurboFLASH sequence with its ultrashort repetition times is not readily amenable to this scheme. This report demonstrates the implementation of a modified TurboFLASH sequence for FAIR imaging. Intravascular suppression is achieved with a modified preparation period that includes a driven equilibrium Fourier transform (DEFT) combination of 90°–180°–90° hard RF pulses subsequent to the inversion delay. These pulses rotate the perfusion‐prepared magnetization into the transverse plane where it can experience the suitably placed diffusion gradients before being returned to the longitudinal direction by the second 90° pulse. A value of b = 20–30 s/mm2 was thereby found to suppress the majority of the intravascular signal. For single‐slice perfusion imaging, quantification is only slightly modified. The technique can be readily extended to multislice acquisition if the evolving flow signal after the DEFT preparation is considered. An advantage of the modified preparation scheme is evident in the multislice FAIR images by the preservation of the sign of the magnetization difference. Magn Reson Med 49:341–350, 2003. © 2003 Wiley‐Liss, Inc.
High‐resolution 3D proton spectroscopic imaging of the human brain at 3 T: SNR issues and application for anatomy‐matched voxel sizes
Authors: Gruber Stephan , Mlynárik Vladimir , Moser Ewald 
Published: January 2003

AbstractIn a systematic study on the interdependence of linewidth, signal‐to‐noise ratio (SNR), and spatial resolution in 3D proton spectroscopic imaging (1H‐SI) at 3 T, we demonstrate reduced linewidths with increased spatial resolution due to reduced magnetic inhomogeneity within the brain. High‐precision quantitative data (0.75–0.094 cm3) were obtained for all resolutions, enabling the creation of metabolic maps that display details such as the ventricles, sulci, and gyri. High‐resolution 1H‐SI allows differences in metabolic ratios to be estimated for anatomically defined regions in gray (GM) and white matter (WM). Seven distinct regions in a healthy brain were anatomically segmented and their metabolic ratios were compared quantitatively. Data from a tumor patient are also presented to demonstrate potential clinical applications. Because of the high resolution, the metabolite ratios could be determined for distinct pathologic regions within the tumor and its surroundings. The method was additionally applied to a patient with patchy Pelizaeus Merzbacher disease (PMD), and compared to single‐voxel spectroscopy performed in the same session. High‐resolution SI data were demonstrated in our study to allow the direct matching of anatomic and metabolic images. This may enhance the clinical value of 1H‐SI. Magn Reson Med 49:299–306, 2003. © 2003 Wiley‐Liss, Inc.
In vivo 31P magnetic resonance spectroscopy of human brain at 7 T: An initial experience
Authors: Lei Hao , Zhu Xiao‐Hong , Zhang Xiao‐Liang , Ugurbil Kamil , Chen Wei 
Published: January 2003

AbstractIn vivo 31P spectra were acquired from the human primary visual cortex at 7 T. The relaxation times of the cerebral metabolites, intracellular pH, rate constant (kf) of the creatine kinase (CK) reaction, and nuclear Overhauser enhancement (NOE) on the detected phosphorus moieties from irradiation of the water spins were measured from normal subjects. With a 5‐cm‐diameter surface coil, 3D 31P chemical shift imaging was performed with a spatial resolution of 7.5 ml and an acquisition resolution of 8 min, resulting in a signal‐to‐noise ratio (SNR) for phosphocreatine (PCr) resonance of 32. The apparent T1 and T2 of PCr measured at 7 T were 3.37 ± 0.29 s and 132.0 ± 12.8 ms, respectively, which were considerably longer than those of adenosine triphosphate (ATP) (T1: 1.02–1.27 s; T2: 25–26 ms). The NOE measured in this study was 24.3% ± 1.6% for PCr, and 10% for ATP. The kf measured in the human primary visual cortex was 0.24 ± 0.03 s−1. The results from this study suggest that ultra‐high‐field strength is advantageous for performing in vivo 31P magnetic resonance spectroscopy (MRS) in the human brain. Magn Reson Med 49:199–205, 2003. © 2003 Wiley‐Liss, Inc.
Quantification of renal perfusion using an intravascular contrast agent (part 1): Results in a canine model
Authors: Aumann Silke , Schoenberg Stefan O. , Just Armin , Briley‐Saebo Karen , Bjørnerud Atle , Bock Michael , Brix Gunnar 
Published: January 2003

AbstractIn this work absolute values of regional renal blood volume (rRBV) and flow (rRBF) are assessed by means of contrast‐enhanced (CE) MRI using an intravascular superparamagnetic contrast agent. In an animal study, eight foxhounds underwent dynamic susceptibility‐weighted MRI upon injection of contrast agent. Using principles of indicator dilution theory and deconvolution analysis, parametric images of rRBV, rRBF, and mean transit time (MTT) were computed. For comparison, whole‐organ blood flow was determined invasively by means of an implanted flow probe, and the weight of the kidneys was evaluated postmortem. A mean rBV value of 28 ml/100 g was found in the renal cortex, with a corresponding mean rBF value of 524 ml/100 g/min and an average MTT of about 3.4 s. Although there was a systematic difference between the absolute blood flow values determined by MRI and the ultrasonic probe, a significant correlation (rs = 0.72, P < 0.05) was established. The influence of the arterial input function (AIF), T1 relaxation effects, and repeated measurements on the precision of the perfusion quantitation is discussed. Magn Reson Med 49:276‐287, 2003. © 2003 Wiley‐Liss, Inc.
Quantification of renal perfusion abnormalities using an intravascular contrast agent (part 2): Results in animals and humans with renal artery stenosis
Authors: Schoenberg Stefan O. , Aumann Silke , Just Armin , Bock Michael , Knopp Michael V. , Johansson Lars O. , Ahlstrom Hakan 
Published: January 2003

AbstractThe interrelation between the morphologic degree of renal artery stenosis and changes in parenchymal perfusion is assessed using an intravascular contrast agent. In seven adult foxhounds, different degrees of renal artery stenosis were created with an inflatable clamp implanted around the renal artery. Dynamic susceptibility‐weighted gradient‐echo imaging was used to measure signal‐time curves in the renal artery and the renal parenchyma during administration of 1.5 mg/kg BW of an intravascular ultrasmall particle iron oxide (USPIO) contrast agent. From the dynamic series, regional renal blood volume (rRBV), regional renal blood flow (rRBF), and mean transit time (MTT) were calculated. The morphologic degree of stenosis was measured in the steady state using a high‐resolution 3D contrast‐enhanced (CE) MR angiography (MRA) sequence (voxel size = 0.7 × 0.7 × 1 mm3). Five patients with renoparenchymal damage due to long‐standing renal artery stenosis were evaluated. In the animal stenosis model, cortical perfusion remained unchanged for degrees of renal artery stenosis up to 80%. With degrees of stenoses > 80%, cortical perfusion dropped to 151 ± 54 ml/100 g of tissue per minute as compared to a baseline of 513 ± 76 ml/100 g/min. In the patients, a substantial difference in the cortical perfusion of more than 200 ± 40 ml/100 g/min between the normal and the ischemic kidneys was found. The results show that quantitative renal perfusion measurements in combination with 3D‐CE‐MRA allow the functional significance of a renal artery stenosis to be determined in a single MR exam. Differentiation between renovascular and renoparenchymal disease thus becomes feasible. Magn Reson Med 49:288–298, 2003. © 2003 Wiley‐Liss, Inc.
The carnosine C‐2 proton's chemical shift reports intracellular pH in oxidative and glycolytic muscle fibers
Authors: Damon Bruce M. , Hsu Alex C. , Stark Heather J. , Dawson M. Joan 
Published: January 2003

AbstractThe appearance of new peaks in the 7.7–8.6 and 6.8–7.4 ppm regions of the postexercise 1H spectrum of frog muscle is reported. These new peaks result from the splitting of single pre‐exercise carnosine C‐2 and C‐4 peaks into two peaks, representing the intracellular pH (pHI) of oxidative and glycolytic fibers. The following data support this conclusion: 1) comparison of means and regression analysis indicates equivalence of the pHI measurements by 1H and 31P NMR; 2) the pre‐ and poststimulation concentrations of carnosine are equal; 3) in ischemic rat hindlimb muscles, the presence of a single, more acidic peak in the plantaris; a single, less acidic peak in the soleus; and two peaks (more and less acidic) in the gastrocnemius correspond to published values for the fiber‐type composition of these muscles; and 4) in muscles treated with iodoacetate prior to and during stimulation, a second peak never appears. These data indicate that it is feasible to measure separately the pHI of oxidative and glycolytic fibers using 1H NMR spectroscopy. Magn Reson Med 49:233–240, 2003. © 2003 Wiley‐Liss, Inc.
Oscillating gradient measurements of water diffusion in normal and globally ischemic rat brain
Authors: Does Mark D. , Parsons Edward C. , Gore John C. 
Published: January 2003

AbstractOscillating gradients were used to probe the diffusion‐time/frequency dependence of water diffusion in the gray matter of normal and globally ischemic rat brain. In terms of a conventional definition of diffusion time, the oscillating gradient measurements provided the apparent diffusion coefficient (ADC) of water with diffusion times between 9.75 ms and 375 μs, an order of magnitude shorter than previously studied in vivo. Over this range, ADCs increased as much as 24% in vivo and 50% postmortem, depending on the nature of the oscillating gradient waveform used. Novel waveforms were employed to sample narrow frequency bands of the so‐called diffusion spectrum. This spectral description of ADC includes the effects of restriction and/or flow, and is independent of experimental parameters, such as diffusion time. The results in rat brain were found to be consistent with restricted diffusion and the known micro‐anatomy of gray matter. Differences between normal and postmortem data were consistent with an increase in water restriction and/or a decrease in flow, and tentatively suggest that physical changes following the onset of ischemia occur on a scale of about 2 μm, similar to a typical cellular dimension in gray matter. Magn Reson Med 49:206–215, 2003. © 2003 Wiley‐Liss, Inc.
Undersampled projection reconstruction for active catheter imaging with adaptable temporal resolution and catheter‐only views
Authors: Peters Dana C. , Lederman Robert J. , Dick Alexander J. , Raman Venkatesh K. , Guttman Michael A. , Derbyshire J. Andrew , McVeigh Elliot R. 
Published: January 2003

AbstractIn this study undersampled projection reconstruction (PR) was used for rapid catheter imaging in the heart, employing steady‐state free precession (SSFP) contrast. Active catheters and phased‐array coils were used for combined imaging of anatomy and catheter position in swine. Real‐time imaging of catheter position was performed with relatively high spatial and temporal resolution, providing 2 × 2 × 8 mm spatial resolution and four to eight frames per second. Two interactive features were introduced. The number of projections (Np) was adjusted interactively to trade off imaging speed and artifact reduction, allowing acquisition of high‐quality or high‐frame‐rate images. Thin‐slice imaging was performed, with interactive requests for thick‐slab projection images of the signal received solely from the active catheter. Briefly toggling on catheter‐only projection images was valuable for verifying that the catheter tip was contained within the selected slice, or for locating the catheter when part of it was outside the selected slice. Magn Reson Med 49:216–222, 2003. Published 2003 Wiley‐Liss, Inc.
MRI‐guided coronary catheterization and PTCA: A feasibility study on a dog model
Authors: Serfaty Jean‐Michel , Yang Xiaoming , Foo Thomas K. , Kumar Ananda , Derbyshire Andrew , Atalar Ergin 
Published: January 2003

AbstractThe aim of this work was to demonstrate the feasibility of MRI‐guided coronary artery catheterization and intervention in a dog model. Experiments were performed on 10 healthy dogs. A 9F introducer sheath was placed through a right carotid artery cutdown. A prototype 0.014‐inch coronary MRI guidewire, a prototype 7 French MRI‐guiding catheter, and two flexible surface coils were connected to a GE 1.5 T CV/i scanner for simultaneous visualization of the guidewire, guiding catheter, and chest anatomy. Images were displayed in real time on an in‐room monitor. A nongated, single‐slice fast gradient‐echo sequence was used to obtain real‐time images of the catheters and background anatomy during the intervention. Fifteen selective catheterizations were attempted in the coronary arteries, and all were successful. Selective injection of diluted gadolinium into the MRI‐guiding catheter provided dynamic 2D projection coronary angiography in all cases, confirming successful catheterization. Percutaneous transluminal coronary angioplasty (PTCA) was attempted after two catheterizations, and all attempts were successful. Inflation of the balloon angioplasty catheter was performed successfully in the left anterior and circumflex arteries. Our results indicate that coronary artery catheterization and intracoronary balloon angioplasty are feasible with MRI guidance only. MRI guidance may be used as an alternative to X‐ray guidance in coronary artery interventions in the future. Magn Reson Med 49:258–263, 2003. © 2003 Wiley‐Liss, Inc.
Effects of FK506 on myasthenia gravis patients with high interleukin‐2 productivity in peripheral blood mononuclear cells
Authors: Utsugisawa Kimiaki , Nagane Yuriko , Yonezawa Hisashi , Obara Daiji , Kondoh Ryushi , Tohgi Hideo 
Published: January 2003

AbstractWe compared the early effects of FK506 on clinical severity, interleukin‐2 (IL‐2) production by phytohemagglutinin‐stimulated peripheral blood mononuclear cells (PBMs), and serum levels of acetylcholine receptor antibodies between myasthenia gravis (MG) patients with elevated (>1250 pg/ml, n = 9) or normal (<1250 pg/mL, n = 10) levels of PBM IL‐2 production. Reduction in clinical severity and PBM IL‐2 production were significantly greater in the patients with elevated IL‐2 production than those with normal PBM IL‐2 production in the first month of treatment. Muscle Nerve 27: 245–248, 2003
Preservation stability and in vivo administration of albumin–heme hybrid solution as an entirely synthetic O2‐carrier
Authors: Tsuchida Eishun , Komatsu Teruyuki , Yanagimoto Tetsuya , Sakai Hiromi 
Published: January 2003

AbstractThe recombinant human serum albumin incorporating a tetraphenylporphyrinatoiron(II) derivative with a covalently linked proximal base (rHSA‐FeP) is an entirely synthetic O2‐carrier as a red blood cell substitute. It shows long‐term preservation stability of both solution properties and O2‐binding ability over a broad temperature range including room temperature. The physicochemical parameters of the rHSA‐Fe(II)P solution ([rHSA]: 5 wt%) stored at 5–40 °C have remained constant over one year. The in vivo safety of this material was also studied by the survival tests and clinical blood chemistry assays. All rats given the 5 wt% rHSA‐Fe(II)P solution have been alive for 14 days after the infusion. During the observation period, no remarkable reaction was seen in the appearance of the animals. Parameters of the clinical blood serum chemistry were all in the normal ranges, and pathological inspections of the major organs showed no significant infarct in their tissues. Copyright © 2003 John Wiley & Sons, Ltd.