bluuebunny/crossref_metadata_2025_split huggingface dataset:
Is quantification of bolus tracking MRI reliable without deconvolution?
Authors: Perthen Joanna E. , Calamante Fernando , Gadian David G. , Connelly Alan 
Published: September 2002

AbstractBolus tracking data obtained with paramagnetic intravascular tracers are commonly analyzed and quantified by the direct measurement of properties of the tissue concentration‐time curve (e.g., time to peak (TTP)). The measurement of these “summary parameters” is used as an accessible alternative approach to the complex deconvolution procedure, and provides indirect measures of perfusion. However, summary parameters do not take into account differences in arterial input functions (AIFs) or residue functions (R(t)) between patients or studies. Simulations were performed to assess the variability of summary parameters over a realistic range of AIFs and for differing R(t), to establish whether they can be used as reliable measures of tissue perfusion status. Results showed that the value of each summary parameter investigated is highly dependent upon both the AIF and R(t). The referencing of summary parameters to their corresponding value in the AIF or in normal tissue is a method commonly used to normalize results, but this approach did not lead to any measures that were independent of both the AIF and R(t) in this study. The results presented here show that the use of summary parameters requires considerable caution, since tissue or patient types can easily be incorrectly classified due to the effect of variations in patient AIF and R(t). Magn Reson Med 47:61–67, 2002. © 2002 Wiley‐Liss, Inc.
Automatic gradient preemphasis adjustment: A 15‐minute journey to improved diffusion‐weighted echo‐planar imaging
Authors: Schmithorst Vincent J. , Dardzinski Bernard J. 
Published: September 2002

AbstractImage distortion caused by gradient eddy currents is a major problem in the use of diffusion tensor imaging (DTI), as using the uncorrected images for calculation of apparent diffusion coefficient (ADC) and diffusion anisotropy will result in areas of artificially increased anisotropy and ADC at the edge of the images, as well as decreased spatial resolution and accuracy in ADC computations overall. This distortion may be substantially reduced by careful adjustment of the gradient preemphasis unit. A completely automatic method of adjusting the preemphasis unit is proposed which finds the optimal settings for all three gradient directions in approximately 15 min by estimating the magnitudes of the eddy currents at various delay times after a test gradient. The pixel shifts in a 64 × 128 echo‐planar diffusion‐weighted image with a diffusion gradient strength of 30 mT/m were reduced to less than 0.2. Magn Reson Med 47:208–212, 2002. © 2002 Wiley‐Liss, Inc.
On the UNFOLD method
Authors: Tsao Jeffrey 
Published: September 2002

AbstractA graphical formalism is presented, showing that “UNaliasing by Fourier‐encoding the Overlaps Using the temporaL Dimension” (UNFOLD) is equivalent to sampling k‐t‐space in a sheared grid pattern. Discrete regular sampling in k‐t‐space leads to periodic replication of the support region in x‐f‐space. Thus, the maximum acceleration achievable by UNFOLD is equivalent to the maximum packing of support regions in x‐f‐space. When the support region is separable along the x and f axes, the reconstruction can be performed separately for each k. UNFOLD can be combined with SiMultaneous Acquisition of Spatial Harmonics (SMASH) to further accelerate acquisition. However, a straightforward combination of the methods has been shown to result in a size restriction, which limits the portion of the field of view (FOV) with a larger temporal bandwidth to only a quarter of the FOV. Two solutions are presented to overcome this restriction. Magn Reson Med 47:202–207, 2002. © 2002 Wiley‐Liss, Inc.
Reconstruction of carotid bifurcation hemodynamics and wall thickness using computational fluid dynamics and MRI
Authors: Steinman David A. , Thomas Jonathan B. , Ladak Hanif M. , Milner Jaques S. , Rutt Brian K. , Spence J. David 
Published: September 2002

AbstractA thorough understanding of the relationship between local hemodynamics and plaque progression has been hindered by an inability to prospectively monitor these factors in vivo in humans. In this study a novel approach for noninvasively reconstructing artery wall thickness and local hemodynamics at the human carotid bifurcation is presented. Three‐dimensional (3D) models of the lumen and wall boundaries, from which wall thickness can be measured, were reconstructed from black‐blood magnetic resonance imaging (MRI). Along with time‐varying inlet/outlet flow rates measured via phase contrast (PC) MRI, the lumen boundary was used as input for computational fluid dynamic (CFD) simulation of the subject‐specific flow patterns and wall shear stresses (WSSs). Results from a 59‐year‐old subject with early, asymptomatic carotid artery disease show good agreement between simulated and measured velocities, and demonstrate a correspondence between wall thickening and low and oscillating shear at the carotid bulb. High shear at the distal internal carotid artery (ICA) was also colocalized with higher WSS; however, a quantitative general relationship between WSS and wall thickness was not found. Similar results were obtained from a 23‐year‐old normal subject. These findings represent the first direct comparison of hemodynamic variables and wall thickness at the carotid bifurcation of human subjects. The noninvasive nature of this image‐based modeling approach makes it ideal for carrying out future prospective studies of hemodynamics and plaque development or progression in otherwise healthy subjects.
Separation and quantification of perfusion and BOLD effects by simultaneous acquisition of functional I0‐ and T‐parameter maps
Authors: Schulte A.‐C. , Speck O. , Oesterle C. , Hennig J. 
Published: September 2002

AbstractThe nature of the coupling between neuronal activity and the hemodynamic response is the subject of intensive research. As a means to simultaneously measure parametric changes of T, initial intensity (I0) and perfusion with high temporal resolution, a multi‐image EPI technique with slice‐selective inversion recovery (ssIR) for arterial spin labeling was developed and implemented. Comparative measurements with and without the preceding slice‐selective inversion pulse were performed. I0 and R changes induced by primary visual stimulation were separated. For ssIR‐multi‐image EPI the average change of I0 over all 12 subjects was 3.4%, corresponding to a perfusion change of 40 ml/min/100 g, whereas only minor I0 changes were observed without inversion. On average, the R of the activated pixels changed by –0.62 sec−1 without inversion, while a significantly reduced average R change of –0.46 sec−1 was calculated for ssIR‐multi‐image EPI due to a decreased BOLD effect contribution of the intravascular compartment. Magn Reson Med 45:811–816, 2001. © 2001 Wiley‐Liss, Inc.
Assessment of experimental autoimmune neuritis in the rat by electrophysiology of the tail nerve
Authors: Kafri Michal , Drory Vivian E. , Wang Ningshan , Rabinowitz Ruth , Korczyn Amos D. , Chapman Joab 
Published: September 2002

AbstractThe assessment of experimental autoimmune neuritis (EAN) by electrophysiological studies of the sciatic innervation of the plantar muscle may be complicated by local inflammation. We therefore utilized the tail nerve–muscle system to monitor disease progression in 20 rats with EAN and 10 control rats. Early changes were detected in motor nerve conduction velocity (32.06 ± 1.85 m/s versus 43.57 ± 3.98 m/s in controls, P < 0.001) at 15 days postimmunization (DPI), and conduction block (70.6 ± 9.4% compared to 12.4 ± 3.4%, P < 0.001) at 22 DPI. No consistent conduction block (22.4 ± 10.4%) was found in the plantar muscle measurements. The tail nerve response of EAN rats demonstrated severe temporal dispersion at 43 DPI, which returned to normal at 135 DPI, although motor nerve conduction velocity values were still lower than in controls (24.4 ± 0.9 m/s, P < 0.001). The tail nerve may be a useful addition to electrophysiological studies in this model of the Guillain–Barré syndrome. © 2002 John Wiley & Sons, Inc. Muscle Nerve 25: 51–57, 2002
Ventral polyradiculopathy with pediatric acute lymphocytic leukemia
Authors: Anderson Stephen C. , Baquis George D. , Jackson Anthony , Monteleone Philip , Kirkwood J. Robert 
Published: September 2002

AbstractA 3‐year‐old girl with acute lymphocytic leukemia (ALL) in remission developed lower extremity paraparesis and areflexia 15 days after receiving intrathecal methotrexate, cytarabine, and hydrocortisone. Cerebrospinal fluid protein was 107 mg/dl. Compound muscle action potential amplitudes were reduced, F waves were absent, and sensory conduction studies were normal. Needle electromyography (EMG) revealed reduced motor unit potential recruitment. Magnetic resonance imaging (MRI) showed lumbosacral ventral root enhancement. She was treated with intravenous immunoglobulin and slowly recovered. Nerve conduction and EMG abnormalities correlated with MRI root enhancement, facilitated early diagnosis, and distinguished this from a myelopathy or distal polyneuropathy. These findings could represent selective ventral nerve root vulnerability to intrathecal chemotherapy. A selective autoimmune process cannot be excluded. © 2002 John Wiley & Sons, Inc. Muscle Nerve 25: 106–110, 2002
Magnetization transfer in MRI: a review
Authors: Henkelman R. M. , Stanisz G. J. , Graham S. J. 
Published: September 2002

AbstractThis review describes magnetization transfer (MT) contrast in magnetic resonance imaging. A qualitative description of how MT works is provided along with experimental evidence that leads to a quantitative model for MT in tissues. The implementation of MT saturation in imaging sequences and the interpretation of the MT‐induced signal change in terms of exchange processes and direct effects are presented. Finally, highlights of clinical uses of MT are outlined and future directions for investigation proposed. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

Beff

effective magnetic field

CRMG

Carr–Purcell–Meiboom–Gill

CW

continuous wave

FAIR

flow sensitive alternating inversion recovery

Gd‐DTPA

gadolinium diethylenetriminepentaacetic acid

MRA

magnetic resonance angiography

MRI

magnetic resonance imaging

MS

multiple sclerosis

MT

magnetization transfer

MTR

magnetization transfer ratio

RF

radio frequency

SAR

specific absorption rate.
Studies of metabolic compartmentation and glucose transport using in vivo MRS
Authors: Rothman Douglas L. 
Published: September 2002

AbstractOrgans consist of several types of cells with specialized functions. This cellular localization of function is often referred to as compartmentation. Due to the intrinsic low sensitivity of MR methods it is generally not possible in vivo to obtain images or spectra of single cells. Instead the MRS signal is the sum of the signal from millions of cells and multiple cell types. A major challenge in using MRS to study biological processes such as metabolism and transport is to devise measurements that provide cell‐specific information from this mix. Fortunately nature has helped the MR scientist by in several cases nearly completely localizing metabolic pathways and their associated metabolites in specific cell types. The chemical specificity of MRS allows the concentrations and synthesis rates of these metabolites to be measured, providing information about the compartmentation of metabolism and function. In this review examples are presented from MRS studies of metabolic trafficking between neurons and astrocytes in the brain, brain glucose transport, and the role of muscle glucose transport in insulin resistance and diabetes. The concepts and approaches used in these studies are generally applicable for studying cellular metabolic compartmentation in a wide range of systems. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

FFA

free fatty acid

MM

Michaelis–Menton

NIDDM

noninsulin‐dependant diabetes mellitus

PAG

phosphate activated glutaminase.
MR spectroscopy quantitation: a review of frequency domain methods
Authors: Mierisová Šárka , Ala‐Korpela Mika 
Published: September 2002

AbstractThere has been a vast increase in applications of magnetic resonance spectroscopy (MRS) in biomedical research during the last few years. This is not surprising since MRS provides both in vivo and in vitro a non‐invasive tool for various biochemical and biomedical studies. There are also expectations that clinical MRS will have an important role as a diagnostic tool. An essential prerequisite for the future success of MRS for applicability in biomedical sciences will be accurate and biochemically relevant data analysis (at as high a level of automation as possible). This review briefly describes principles of the methodology available for advanced quantitative data analysis in the frequency domain. Various biomedical applications are discussed in order to illustrate the practical aspects of the analyses and to show the applicability and power of biochemical prior knowledge‐based lineshape fitting analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

Asp

aspartate

Cho

choline

Cr

creatine

EMCL

extra‐myocellular lipids

FID

free induction decay

FT

Fourier transform

GABA

γ‐aminobutyric acid

Glu

glutamate

Gln

glutamine

Glc

glucose

GPC

glycerophosphocholine

GPE

glycerophosphoethanolamine

HDL

high density lipoprotein

IDL

intermediate density lipoprotein

IMCL

intra‐myocellular lipids

LDL

low density lipoprotein

Pi

inorganic phosphate

myo‐Ins

myo‐inositol

NAA

N‐acetyl‐aspartate

NAAG

N‐acetylaspartylglutamate

NTP

nucleotide triphosphates

PC

phosphocholine

PCr

phosphocreatine

PDE

phosphodiesters

PE

phosphoethanolamine

PME

phosphomonoesters

scyllo‐Ins

scyllo‐inositol

SNR

signal‐to‐noise ratio

Tau

taurine

TDFD

frequency domain fitting using time domain models

TLS

total lineshape

TSP

sodium 3‐trimethylsilyl[2,2,3,3‐D4] propionate

VLDL

very low density lipoprotein.
NMR spectral quantitation by principal component analysis
Authors: Stoyanova R. , Brown T. R. 
Published: September 2002

AbstractThe use of principal component analysis (PCA) for simultaneous spectral quantitation of a single resonant peak across a series of spectra has gained popularity among the NMR community. The approach is fast, requires no assumptions regarding the peak lineshape and provides quantitation even for peaks with very low signal‐to‐noise ratio. PCA produces estimates of all peak parameters: area, frequency, phase and linewidth. If desired, these estimates can be used to correct the original data so that the peak in all spectra has the same lineshape. This ability makes PCA useful not only for direct peak quantitation, but also for processing spectral data prior to application of pattern recognition/classification techniques. This article briefly reviews the theoretical basis of PCA for spectral quantitation, addresses issues of data processing prior to PCA, describes suitable and unsuitable datasets for PCA applications and summarizes the developments and the limitations of the method. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

PCA

principal component analysis.
Expression and localization of agrin during sympathetic synapse formation in vitro
Authors: Gingras Jacinthe , Ferns Michael 
Published: September 2002

AbstractAgrin is a motoneuron‐derived signaling factor that plays a key organizing role in the initial stages of neuromuscular synapse formation. Agrin is expressed in other regions of the developing central and peripheral nervous systems, however, raising the possibility that it also directs the formation of some interneuronal synapses. To address this question, we have examined the expression and localization of agrin during formation of cholinergic, interneuronal synapses in the sympathetic system. In the superior cervical ganglia (SCG) in vivo, we found that agrin is highly expressed, and that it is present at, but is not limited to, synapses. In SCG neuronal cultures that were treated with ciliary neurotrophic factor to induce a uniform cholinergic phenotype, we found that agrin immunostaining colocalized precisely with cholinergic terminals and aggregates of neuronal acetylcholine receptor on the neuronal cell bodies and dendrites. Moreover, we found that α‐dystroglycan, which is a potential receptor for agrin, is also concentrated at these cholinergic synaptic contacts. Finally, the SCG neurons expressed the C‐terminal isoform of agrin that is neural‐specific and highly active in synaptogenesis, and also the N‐terminal splice isoform that occurs as a type II transmembrane protein. These findings show that agrin is specifically localized at sympathetic synapses in vitro, and are consistent with it playing a role in interneuronal synapse formation. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 228–242, 2001
Quality awards as a public sector benchmarking concept in OECD member countries: some guidelines for quality award organizers
Authors: Löffler Elke 
Published: September 2002

AbstractIn many OECD member countries, quality awards have become an important benchmarking instrument for public and especially private sector organizations. Quality awards pursue two main goals: one is to introduce elements of competition in areas of the public and the private sectors that lack of market competition; the other is to encourage organizational learning. The problem is that in a public sector context these aims seem to be mutually exclusive. The aim of the article is to show quality award organizers how to realize the full potential of quality awards by making the appropriate choices in the design of a public sector quality award. The conclusion is that the stage of public sector quality management and the degree of ‘publicness’ of the public sector in a given country will influence the competition‐inducing and learning effect of a national quality award in an adverse way. Nevertheless, the negative effects on one or the other element of quality awards can be counterbalanced by the appropriate choice of the scope of the quality award, the area to be evaluated, the evaluation criteria as well as the benchmarking concept. Last but not least, quality award organizers should keep in mind that quality awards are not a benchmarking instrument for all seasons. Copyright © John Wiley & Sons, Ltd.
Incentive Effects of Expanding Federal Mass Transit Formula Grants
Authors: Schmidt Stephen 
Published: September 2002

AbstractPublic subsidies to industries firms incentives to alter their behavior. When calculating the effects of such programs, previous assessments of transit subsidies have not included the effects of these incentives on the firms' output. This article reports the responses of mass transit firms to the federal transit subsidy program and changes the Transportation Equity Act for the 21st Century (TEA 21) made to that program, as predicted by a structural model of output choice. TEA 21 increases bus service in medium‐sized cities by 6‐8 percent, butincreases service in large cities by only 1‐2 percent. The formula's incentive tier is weak, and the size of the subsidy depends little on whether that output results in increased ridership. The formula could be redesigned to provide stronger incentives to lower cost and increase ridership, thus encouraging a more efficient response from transit firms. © 2001 by the Association for Public Policy Analysis and Management.
Cases and Controversies: How Novitiates Are Trained to Be Masters of the Public Policy Universe
Authors: Chetkovich Carol , Kirp David L. 
Published: September 2002

AbstractPublic policy schools were established 30 years ago to provide analytic and management skills to aspiring policy professionals. A centerpiece of policy management training has been the action‐centered teaching case, modeled after the cases long used in business schools. Though other aspects of public management teaching and research have been vigorously debated, little attention has been paid to the content of teaching cases.Taking these texts as a central element in policy student socialization, the authors ask what implicit lessons they convey. A close reading of 10 best‐selling cases from the Kennedy School of Government finds the policy world to be the domain of high‐level, lone protagonists beset by hostile political forces; collaborative problem‐solving is rare, street‐level actors insignificant, and historical, social, and institutional contexts of minimal importance. The article discusses the implications of this construction and raises questions about its appropriateness for the training of future public servants. © 2001 by the Association for Public Policy Analysis and Management.
Synthesis and characterization of new soluble polyamides derived from 2,6‐bis(4‐aminophenyl)‐3,5‐dimethyltetrahydro‐4H‐pyran‐4‐one
Authors: García José M. , García Félix , Sanz Roberto , de la Campa José G. , Lozano Angel E. , de Abajo Javier 
Published: September 2002

AbstractA new oxypyrone diamine, 2,6‐bis(4‐aminophenyl)‐3,5‐dimethyltetrahydro‐4H‐pyran‐4‐one (DAPP), was prepared from 4‐nitrobenzaldehyde and 3‐oxa‐n‐pentane in a two‐step reaction with a high yield and a high purity. Aromatic polyamides were obtained from this novel condensation monomer and several diacid chlorides through the conventional low‐temperature solution method in N,N‐dimethylacetamide. Polycondensation results were consistent with a high reactivity for DAPP because high yields and high molecular weight polyamides were obtained with inherent viscosities up to 1.8 dL/g. The reactivity of DAPP was also estimated with theoretical calculations from computer programs for molecular simulation, with orbital and charge factors considered. The polymers showed improved solubility in organic solvents, relative to conventional wholly aromatic polyamides, and high glass‐transition temperatures (from differential scanning calorimetry) over 270 °C. However, the thermal resistance, as estimated by thermogravimetric analysis, was lower than that of conventional aromatic polyamides; nevertheless, decomposition temperatures well beyond 300 °C were observed in nitrogen and air. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1825–1832, 2001
Wave formation by heating in thin metal film on an elastomer
Authors: Kim Jinook , Lee Hong H. 
Published: September 2002

AbstractWave formation by heating rather than the usual cooling in a thin metal film on an elastomer is presented. A simple model is used to relate the wavelength of the waves thus formed to the heating temperature. An indirect method of estimating Young's modulus at elevated temperatures emerges from the analysis. The waves formed by heating can be made to appear or not to appear by the selection of the temperature to which the sample is heated. A relationship is given for the critical temperature that determines the appearance or nonappearance of the waves. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1122–1128, 2001