bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of hepatic perfusion parameters with dynamic MRI
Authors: Materne R. , Smith A.M. , Peeters F. , Dehoux J.P. , Keyeux A. , Horsmans Y. , Van Beers B.E. 
Published: September 2002

AbstractQuantification of hepatic perfusion parameters greatly contributes to the assessment of liver function. The purpose of this study was to describe and validate the use of dynamic MRI for the noninvasive assessment of hepatic perfusion parameters. The signal from a fast T1‐weighted spoiled gradient‐echo sequence preceded by a nonslice‐selective 90° pulse and a spoiler gradient was calibrated in vitro with tubes filled with various gadolinium concentrations. Dynamic images of the liver were obtained after intravenous bolus administration of 0.05 mmol/kg of Gd‐DOTA in rabbits with normal liver function. Hepatic, aortic, and portal venous signal intensities were converted to Gd‐DOTA concentrations according to the in vitro calibration curve and fitted with a dual‐input one‐compartmental model. With MRI, hepatic blood flow was 100 ± 35 mL min‐1 100 mL‐1, the arterial fraction 24 ± 11%, the distribution volume 13.0 ± 3.7%, and the mean transit time 8.9 ± 4.1 sec. A linear relationship was observed between perfusion values obtained with MRI and with radiolabeled microspheres (r = 0.93 for hepatic blood flow [P < 0.001], r = 0.79 for arterial blood flow [P = 0.01], and r = 0.91 for portal blood flow [P < 0.001]). Our results indicate that hepatic perfusion parameters can be assessed with dynamic MRI and compartmental modeling. Magn Reson Med 47:135–142, 2002. © 2002 Wiley‐Liss, Inc.
Highly diffusion‐sensitized MRI of brain: Dissociation of gray and white matter
Authors: Yoshiura Takashi , Wu Ona , Zaheer Atif , Reese Timothy G. , Sorensen A. Gregory 
Published: September 2002

AbstractThe brains of six healthy volunteers were scanned with a full tensor diffusion MRI technique to study the effect of a high b value on diffusion‐weighted images (DWIs). The b values ranged from 500 to 5000 s/mm2. Isotropic DWIs, trace apparent diffusion coefficient (ADC) maps, and fractional anisotropy (FA) maps were created for each b value. As the b value increased, ADC decreased in both the gray and white matter. Furthermore, ADC of the white matter became lower than that of the gray matter, and, as a result, the white matter became brighter than the gray matter in the isotropic DWIs. Quantitative analysis showed that these changes were due to nonmonoexponential diffusion signal decay of the brain tissue, which was more prominent in white matter than in gray matter. There was no significant change in relation to the b value in the FA maps. High b value appears to have a dissociating effect on gray and white matter in DWIs. Magn Reson Med 45:734–740, 2001. © 2001 Wiley‐Liss, Inc.
Analysis of partial volume effects in diffusion‐tensor MRI
Authors: Alexander Andrew L. , Hasan Khader M. , Lazar Mariana , Tsuruda Jay S. , Parker Dennis L. 
Published: September 2002

AbstractThe diffusion tensor is currently the accepted model of diffusion in biological tissues. The measured diffusion behavior may be more complex when two or more distinct tissues with different diffusion tensors occupy the same voxel. In this study, a partial volume model of MRI signal behavior for two diffusion‐tensor compartments is presented. Simulations using this model demonstrate that the conventional single diffusion tensor model could lead to highly variable and inaccurate measurements of diffusion behavior. The differences between the single and two‐tensor models depend on the orientations, fractions, and exchange between the two diffusion tensor compartments, as well as the diffusion‐tensor encoding technique and diffusion‐weighting that is used in the measurements. The current single compartment model's inaccuracies could cause diffusion‐based characterization of cerebral ischemia and white matter connectivity to be incorrect. A diffusion‐tensor MRI imaging experiment on a normal human brain revealed significant partial volume effects between oblique white matter regions when using very large voxels and large diffusion‐weighting (b ∼ 2.69 × 103 sec/mm2). However, the apparent partial volume effects in white matter decreased significantly when smaller voxel dimensions were used. For diffusion tensor studies obtained using typical diffusion‐weighting values (b ∼ 1 × 103 sec/mm2) partial volume effects are much more difficult to detect and resolve. More accurate measurements of multiple diffusion compartments may lead to improved confidence in diffusion measurements for clinical applications. Magn Reson Med 45:770–780, 2001. © 2001 Wiley‐Liss, Inc.
Three‐dimensional subzone‐based reconstruction algorithm for MR elastography
Authors: Van Houten Elijah E.W. , Miga Michael I. , Weaver John B. , Kennedy Francis E. , Paulsen Keith D. 
Published: September 2002

AbstractAccurate characterization of harmonic tissue motion for realistic tissue geometries and property distributions requires knowledge of the full three‐dimensional displacement field because of the asymmetric nature of both the boundaries of the tissue domain and the location of internal mechanical heterogeneities. The implications of this for magnetic resonance elastography (MRE) are twofold. First, for MRE methods which require the measurement of a harmonic displacement field within the tissue region of interest, the presence of 3D motion effects reduces or eliminates the possibility that simpler, lower‐dimensional motion field images will capture the true dynamics of the entire stimulated tissue. Second, MRE techniques that exploit model‐based elastic property reconstruction methods will not be able to accurately match the observed displacements unless they are capable of accounting for 3D motion effects. These two factors are of key importance for MRE techniques based on linear elasticity models to reconstruct mechanical tissue property distributions in biological samples. This article demonstrates that 3D motion effects are present even in regular, symmetric phantom geometries and presents the development of a 3D reconstruction algorithm capable of discerning elastic property distributions in the presence of such effects. The algorithm allows for the accurate determination of tissue mechanical properties at resolutions equal to that of the MR displacement image in complex, asymmetric biological tissue geometries. Simulation studies in a realistic 3D breast geometry indicate that the process can accurately detect 1‐cm diameter hard inclusions with 2.5× elasticity contrast to the surrounding tissue. Magn Reson Med 45:827–837, 2001. © 2001 Wiley‐Liss, Inc.
Accurate multislice gradient echo T1 measurement in the presence of non‐ideal RF pulse shape and RF field nonuniformity
Authors: Parker Geoffrey J.M. , Barker Gareth J. , Tofts Paul S. 
Published: September 2002

AbstractA methodology is presented for estimating T1 using a two‐point technique with a standard multislice gradient echo sequence. The method explicitly corrects for the shape of the RF pulse and for spatial variations in transmitted RF field intensity. Including these factors in the calculation of T1 gives a substantial improvement in accuracy and precision of two‐point gradient echo T1 measurements in the presence of RF nonuniformity and non‐ideal pulse profiles. The mean accuracy of the technique was found to be 1.4%. The mean precision was found to be 3.0%. The mean variation along the axis of a head coil was found to be 2.3%. Magn Reson Med 45:838–845, 2001. © 2001 Wiley‐Liss, Inc.
Adaptive sensitivity encoding incorporating temporal filtering (TSENSE)†
Authors: Kellman Peter , Epstein Frederick H. , McVeigh Elliot R. 
Published: September 2002

AbstractA number of different methods have been demonstrated which increase the speed of MR acquisition by decreasing the number of sequential phase encodes. The UNFOLD technique is based on time interleaving of k‐space lines in sequential images and exploits the property that the outer portion of the field‐of‐view is relatively static. The differences in spatial sensitivity of multiple receiver coils may be exploited using SENSE or SMASH techniques to eliminate the aliased component that results from undersampling k‐space. In this article, an adaptive method of sensitivity encoding is presented which incorporates both spatial and temporal filtering. Temporal filtering and spatial encoding may be combined by acquiring phase encodes in an interleaved manner. In this way the aliased components are alternating phase. The SENSE formulation is not altered by the phase of the alias artifact; however, for imperfect estimates of coil sensitivities the residual artifact will have alternating phase using this approach. This is the essence of combining temporal filtering (UNFOLD) with spatial sensitivity encoding (SENSE). Any residual artifact will be temporally frequency‐shifted to the band edge and thus may be further suppressed by temporal low‐pass filtering. By combining both temporal and spatial filtering a high degree of alias artifact rejection may be achieved with less stringent requirements on accuracy of coil sensitivity estimates and temporal low‐pass filter selectivity than would be required using each method individually. Experimental results that demonstrate the adaptive spatiotemporal filtering method (adaptive TSENSE) with acceleration factor R = 2, for real‐time nonbreath‐held cardiac MR imaging during exercise induced stress are presented. Magn Reson Med 45:846–852, 2001. Published 2001 Wiley‐Liss, Inc.
Lumbrical and interossei recording in severe carpal tunnel syndrome
Authors: Boonyapisit Kanokwan , Katirji Bashar , Shapiro Barbara E , Preston David C. 
Published: September 2002

AbstractPatients with severe carpal tunnel syndrome (CTS) may occasionally have absent median motor and sensory responses; in these cases, it is not possible to accurately localize the median mononeuropathy to the wrist using standard electrodiagnostic tests. We prospectively investigated the use of comparing the median motor latency to the second lumbrical and the ulnar motor latency to the interossei muscles in 28 patient hands with severe CTS and absent median motor and sensory responses. We found a prolonged latency difference in 92.8%. Along with its use in mild CTS, study of the lumbrical‐interossei latency difference is helpful in patients with severe CTS with absent median motor and sensory responses. © 2002 John Wiley & Sons, Inc. Muscle Nerve 25: 102–105, 2002
Magnetization transfer MRS
Authors: Leibfritz Dieter , Dreher Wolfgang 
Published: September 2002

AbstractThis review deals with magnetization transfer (MT) effects observed in in vivo NMR spectroscopy. The basic experimental methods of MT experiments, the underlying kinetic mechanisms as well as the evaluation of measured data by fits to two‐ or three‐pool models are described. Experimental results of both 31P and 1H in vivo MRS are reviewed showing the potential of MT experiments to characterize kinetic equilibrium reactions. This includes reactions where all involved components are MR visible, as well as situations where one indirectly measures pools of bound spins which cannot directly be observed in vivo. In particular, MT effects are described which have been observed in in vivo 1H NMR spectra measured on the animal or human brain or on skeletal muscle. Possible mechanisms for the strong MT effects observed for the signals of creatine/phosphocreatine, lactate, alcohol and other metabolites are discussed. It is also emphasized that MT effects caused by water suppression techniques may lead to systematic errors in the quantification of in vivo 1H NMR spectra. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

CIDNP

chemically induced nuclear polarization

NOE

nuclear Overhauser effect

SNR

signal‐to‐noise ratio

TRABI

train of bipolar pulses

2D EXSY

two‐dimensional exchange spectroscopy

MEGA

Mescher–Garwood water suppression

WEFT

water‐eliminated Fourier technique

rf

radio frequency

cw

continuous wave.
Relaxation times and microstructures
Authors: Fenrich F. R. E. , Beaulieu C. , Allen P. S. 
Published: September 2002

AbstractA discussion is presented of the evaluation of multiple relaxation components from water protons in biological tissue. The principal focus is to draw attention to the way in which limitations in the raw NMR data, such as signal‐to‐noise ratio, data sampling density and acquisition window width, affect the precision and resolution in the processed multiple component solution of the return to thermal equilibrium. The second issue discussed is the interpretation of these multiple components in terms of microstructural compartments of the biological sample and, thirdly, we outline some of the successes in determining regional and pathological variations in microstructure in the human body in‐vivo, using the technique of multiple relaxation components. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

CNS

central nervous system

CPMG

Carr–Purcell–Meiboom–Gill sequence

RBC

red blood cells

NMR

nuclear magnetic resonance

NNLS

non‐negative least squares

PNS

peripheral nervous system

SNR

signal‐to‐noise ratio

TE

echo time.
MR spectroscopy quantitation: a review of time‐domain methods
Authors: Vanhamme Leentie , Sundin Tomas , Hecke Paul Van , Huffel Sabine Van 
Published: September 2002

AbstractIn this article an overview of time‐domain quantitation methods is given. Advantages of processing the data in the measurement domain are discussed. The basic underlying principles of the methods are outlined and from them the situations under which these algorithms perform well are derived. Also an overview of methods to preprocess the data is given. In that respect, signal‐to‐noise and/or resolution enhancement, the removal of unwanted components and corrections for model imperfections are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

ARMA

autoregressive moving average

ATP

adenosine triphosphate

EM

expectation ‐ maximization

FIR

finite impulse response

IQML

iterative quadratic maximum likelihood method

ML

maximum likelihood

MP

matrix pencil

NLLS

nonlinear least squares

PCA

principal component analysis

SVD

singular value decomposition

TLS

total least squares.
Automatic quantitation of localized in vivo1H spectra with LCModel
Authors: Provencher Stephen W. 
Published: September 2002

AbstractThe LCModel method analyzes an in vivo spectrum as a Linear Combination of Model in vitro spectra from individual metabolite solutions. Complete model spectra, rather than individual resonances, are used in order to incorporate maximum prior information into the analysis. A nearly model‐free constrained regularization method automatically accounts for the baseline and lineshape in vivo without imposing a restrictive parameterized form on them. LCModel is automatic (non‐interactive) with no subjective input. Approximately maximum‐likelihood estimates of the metabolite concentrations and their uncertainties (Cramér‐Rao lower bounds) are obtained. LCModel analyses of spectra from users with fields from 1.5 to 9.4 T and a wide range of sequences, particularly with short TE, are used here to illustrate the capabilities and limitations of LCModel and proton MRS. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

Ala

alanine

Asp

aspartate

Cr

creatine

GABA

γ‐aminobutyric acid

Glc

glucose

Gln

glutamine

Glu

glutamate

GPC

glycerophosphocholine

GSH

glutathione

Ins

myo‐inositol

Lac

lactate

NAA

N‐acetylaspartate

NAAG

N‐acetylaspartylglutamate

PC

phosphocholine

PCr

phosphocreatine

PE

phosphoethanolamine

Scyllo

scyllo‐inositol

S/N

signal‐to‐noise ratio

Tau

taurine.
Enteric neuroblasts require the phosphatidylinositol 3‐kinase pathway for GDNF‐stimulated proliferation
Authors: Focke Paul J. , Schiltz Craig A. , Jones Sharon E. , Watters Jyoti J. , Epstein Miles L. 
Published: September 2002

AbstractThe enteric nervous system (ENS) develops from neural crest cells that enter the gut, migrate, proliferate, and differentiate into neurons and glia. The growth factor glial‐derived neurotrophic factor (GDNF) stimulates the proliferation and survival of enteric crest‐derived cells. We investigated the intracellular signaling pathways activated by GDNF and their involvement in proliferation. We found that GDNF stimulates the phosphorylation of both the PI 3‐kinase downstream substrate Akt and the MAP kinase substrate ERK in cultures of immunoaffinity‐purified embryonic avian enteric crest‐derived cells. The selective PI 3‐kinase inhibitor LY‐294002 blocked GDNF‐stimulated Akt phosphorylation in purified crest cells, and reduced proliferation in cultures of dissociated quail gut. The ERK kinase (MEK) inhibitors PD 98059 and UO126 did not reduce GDNF‐stimulated proliferation, although PD 98059 blocked GDNF‐stimulated phosphorylation of ERK. We conclude that the PI 3‐kinase pathway is necessary for the GDNF‐stimulated proliferation of enteric neuroblasts. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 306–317, 2001
Prenatal diagnosis of a de novo supernumerary marker derived from chromosome 16
Authors: Hengstschläger Markus , Bettelheim Dieter , Drahonsky Regina , Deutinger Josef , Bernaschek Gerhard 
Published: September 2002

AbstractMarker chromosomes are supernumerary chromosomes of unknown origin and are seldom found in prenatal diagnosis. Application of fluorescent in situ hybridization (FISH) allows the identification of the chromosomal origin of markers. Estimation of the risk of an abnormal phenotype outcome can be enabled by collecting data on phenotypes associated with markers of the same chromosomal origin. So far only very few cases of prenatal diagnosis of de novo supernumerary markers derived from chromosome 16 have been reported. Here the prenatal diagnosis of a de novo supernumerary marker chromosome 16 is described and the relevant literature discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Micellar effect on the reaction of chromium(VI) oxidation of D‐fructose in the presence and absence of picolinic acid in aqueous media: a kinetic study
Authors: Das Asim K. , Roy Aparna , Saha Bidyut , Mohanty Rajani K. , Das Mahua 
Published: September 2002

AbstractThe kinetics and mechanism of the Cr(VI) oxidation of D‐fructose in the presence and absence of picolinic acid (PA) in aqueous acid media were studied under the conditions [D‐fructose]T ≫[Cr(VI)]T at different temperatures. Under the kinetic conditions, the monomeric species of Cr(VI) was found to be kinetically active in the absence of PA whereas in the PA‐catalysed path, the Cr(VI)–PA complex was considered to be the active oxidant. In this path, the Cr(VI)–PA complex undergoes a nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition through glycol splitting leading to the lactone of C5‐aldonic acid along with formaldehyde and the Cr(IV)–PA complex. The primary product formaldehyde undergoes further oxidation (in part) to form formic acid. Then the Cr(IV)–PA complex participates further in the oxidation of D‐fructose and ultimately is converted into the inert Cr(III)–PA complex. In the uncatalysed path, the Cr(VI)–substrate ester experiences an acid‐catalysed redox decomposition (2e transfer) in the rate‐determining step giving rise to the products. The uncatalysed path shows a second‐order dependence on [H+] whereas the PA catalysed path shows a fractional order in [H+]. Both paths show a first‐order dependence on [D‐fructose]T and [Cr(VI)]T. The PA‐catalysed path is first order in [PA]T. All these patterns remain unaltered in the presence of externally added surfactants. The effects of a cationic surfactant, N‐cetylpyridinium chloride (CPC), and an anionic surfactant, sodium dodecyl sulfate (SDS), on both the uncatalysed and PA‐catalysed paths were studied. CPC inhibits both the uncatalysed and PA‐catalysed paths whereas SDS catalyses the reactions. The observed micellar effects are explained by considering a distribution pattern of the reactants between the micellar and aqueous phases. The applicability of different kinetic models, e.g. the pseudo‐phase ion‐exchange model, the Menger–Portnoy model and the Piszkiewicz cooperative model, was tested to explain the observed micellar effects. The effect of [surfactant]T on the activation parameters was explored to rationalize the micellar effect. Copyright © 2001 John Wiley & Sons, Ltd.
Psychosocial interventions for cancer: review and analysis using a three‐tiered outcomes model
Authors: Owen Jason E. , Klapow Joshua C. , Hicken Bret , Tucker Diane C. 
Published: September 2002

AbstractThis study describes a three‐tiered measurement model for psychosocial interventions with cancer patients and compares this model to extant measurement strategies. Progress has been made toward demonstrating that psychosocial interventions reduce depression, anxiety, functional impairment, and symptoms. However, Chambless and Hollon (1998) note that the literature on psychosocial interventions for cancer fails to meet criteria for establishing treatment ‘efficacy’ and does not address issues of cost‐effectiveness. The lack of a timely model of clinical outcomes may be hindering demonstration of efficacy and wider implementation of these interventions. Outcomes assessed by 65 interventions were classified as Global Health Outcomes (medical endpoints, health‐related quality of life (HRQOL), or resource utilization), Dimensions of HRQOL (distress, symptoms, functional ability, or interpersonal well‐being), or Mechanisms of Action (evaluation of psychological or physiological processes). A total of 28% of reviewed studies assessed Global Outcomes, 82% assessed Dimensions of HRQOL, and 49% assessed Mechanisms of Action. While most studies assessed patients' symptoms and distress, measurements of resource utilization, HRQOL, and interpersonal HRQOL were under‐reported. A greater emphasis on treatment costs, quality of life, and mediating/moderating processes associated with improvement in outcomes could inform decisions regarding allocation of health‐care resources and lead to more widely available and efficient interventions for patients. Copyright © 2001 John Wiley & Sons, Ltd.
Supportive groups for siblings of pediatric oncology patients: impact on anxiety
Authors: Houtzager B.A. , Grootenhuis M.A. , Last B.F. 
Published: September 2002

AbstractChildhood cancer can have a substantial emotional impact on the siblings of the sick child. In order to help these siblings adjust to the illness, supportive groups were started in 1994 at our medical center. The program is based on a model of psychosocial support; the aim of the group is to enhance control strategies and, thus, to reduce anxiety. It consists of five sessions and is offered to siblings aged 7–18. The study objective is to evaluate the effect of group participation on sibling anxiety. The State Trait Anxiety Inventory for Children was administered to 24 siblings before and after group participation.Results showed that siblings experience less anxiety after participating in the group. Before group participation, a majority of the siblings were more anxious compared with normal peers. The sibling's age and sex, whether the ill child is in treatment, survival perspective, and time since diagnosis were not related to anxiety reduction. The continuation of the group is supported by its positive impact on siblings. Results must nevertheless be interpreted cautiously, considering the small number of siblings participating in the study, the lack of a control group and the restriction to one outcome measure. Copyright © 2001 John Wiley & Sons, Ltd.