bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous measurement of arterial input function and tumor pharmacokinetics in mice by dynamic contrast enhanced imaging: Effects of transcytolemmal water exchange
Authors: Zhou Rong , Pickup Stephen , Yankeelov Thomas E. , Springer Charles S. , Glickson Jerry D. 
Published: July 2004

AbstractA noninvasive technique for simultaneous measurement of the arterial input function (AIF) for gadodiamide (Omniscan) and its uptake in tumor was demonstrated in mice. Implantation of a tumor at a suitable location enabled its visualization in a cardiac short axis image. Sets of gated, low‐resolution saturation recovery images were acquired from each of five tumor‐bearing mice following intravenous administration of a bolus of contrast agent (CA). The AIF was extracted from the signal intensity changes in left ventricular blood using literature values of the CA relaxivity and a precontrast T1 map. The time‐dependent 1H2O relaxation rate constant (R1 = 1/T1) in the tumor was modeled using the BOLus Enhanced Relaxation Overview (BOLERO) method in two modes regarding the equilibrium transcytolemmal water exchange system: 1) constraining it exclusively to the fast exchange limit (FXL) (the conventional assumption), and 2) allowing its transient departure from FXL and access to the fast exchange regime (FXR), thus designated FXL/FXR. The FXL/FXR analysis yielded better fittings than the FXL‐constrained analysis for data from the tumor rims, whereas the results based on the two modes were indistinguishable for data from the tumor cores. For the tumor rims, the values of Ktrans (the rate constant for CA transfer from the vasculature to the interstitium) and ve (volume fraction of the tissue extracellular and extravascular space) returned from FXL/FXR analysis are consistently greater than those from the FXL‐constrained analysis by a factor of 1.5 or more corresponding to a CA dose of 0.05 mmole/kg. Magn Reson Med 52:248–257, 2004. © 2004 Wiley‐Liss, Inc.
Long component time constant of 23Na T relaxation in healthy human brain
Authors: Bartha Robert , Menon Ravi S. 
Published: July 2004

AbstractSignal intensity in 23Na images is altered in pathologic conditions such as ischemia and may provide information regarding tissue viability complementary to MR diffusion and perfusion imaging. However, the multicomponent transverse relaxation of 23Na (spin 3/2) complicates the determination of tissue sodium concentration from 23Na images with nonzero echo‐time. The purpose of this study was to measure the long component time constant of tissue sodium T relaxation in the healthy human brain at 4 T. Multiecho gradient‐echo 23Na images (10 echo‐times ranging from 3.8–68.7 ms) were acquired in five healthy human volunteers. T was quantified on a pixel‐by‐pixel basis using a nonnegative least squares fitting routine using 100 equally spaced bins between 0.5–99.5 ms and parametric maps were produced representing components between 0.5–3, 3.1–50, 50.1–98, and 98.1–99.5 ms. The long T component of tissue sodium (average ± standard deviation) varied between cortex (occipital = 22.0 ± 2.4 ms), white matter (parietal = 18.2 ± 1.9 ms), and subcortical gray matter (thalamus = 16.9 ± 2.4 ms). These results demonstrate considerable regional variability and establish a foundation for future characterization of 23Na T in conditions such as cerebral ischemia and cancer. Magn Reson Med 52:407–410, 2004. © 2004 Wiley‐Liss, Inc.
Breath‐hold water and fat imaging using a dual‐echo two‐point dixon technique with an efficient and robust phase‐correction algorithm
Authors: Ma Jingfei 
Published: July 2004

AbstractA two‐point Dixon technique using a novel phase‐correction algorithm and commercially available dual‐echo fast gradient‐echo pulse sequence is presented. The phase‐correction algorithm determines the directional rather than phase distribution of signals due to field inhomogeneities. Specifically, a region‐growing scheme uses precalculated spatial gradients of the signal phase to guide the growth sequence, so there is no need to manually select the seeds or use an empirical angular threshold. Further, the determination of the signal direction of a given pixel is based on both the amplitude and phase of the surrounding pixels, the direction of which has already been determined. The advantages of this algorithm include its easy implementation, computational efficiency, and robustness in the presence of pixels with large phase uncertainty. The feasibility and usefulness of the technique are demonstrated in vivo with artifact‐free water and fat images of an entire abdomen in a single breath‐hold. Magn Reson Med 52:415–419, 2004. © 2004 Wiley‐Liss, Inc.
Assessment of tumor blood perfusion by high‐resolution dynamic contrast‐enhanced MRI: A preclinical study of human melanoma xenografts
Authors: Benjaminsen Ilana C. , Graff Bjørn A. , Brurberg Kjetil G. , Rofstad Einar K. 
Published: July 2004

AbstractA noninvasive method to obtain high‐resolution images of tumor blood perfusion is needed for individualized cancer treatments. In this study we investigated the potential usefulness of dynamic contrast‐enhanced MRI (DCE‐MRI), using human melanoma xenografts as models of human cancer. Gadopentetate dimeglumine (Gd‐DTPA) was used as the contrast agent, and DCE‐MRI was performed at a voxel size of 0.5 × 0.2 × 2.0 mm3 with spoiled gradient‐recalled sequences. We obtained images of E · F (where E is the extraction fraction, and F is perfusion) by subjecting DCE‐MR images to Kety analysis. We obtained highly reproducible E · F images, which we verified by imaging heterogeneous tumors twice. We hypothesized that the extraction fraction of Gd‐DTPA would be high and would not vary significantly in tumor tissue, implying that E · F should be a well‐suited parameter for describing tumor blood perfusion. Observations consistent with this hypothesis were made by comparison of E · F‐images with immunostained histological preparations from the imaged sections. The E · F images mirrored the histological appearance of the tumor tissue perfectly. Quantitative studies showed that E · F was highest in nonhypoxic tissue with high microvascular density, second highest in nonhypoxic tissue with low microvascular density, third highest in hypoxic tissue, and lowest in necrotic tissue. Moreover, the radial heterogeneity in E · F was almost identical to that in the blood supply, as assessed by the use of Na99mTcO4 as a perfusion tracer. Taken together, our observations show that high‐resolution images reflecting tumor blood perfusion can be obtained by DCE‐MRI. Magn Reson Med 52:269–276, 2004. © 2004 Wiley‐Liss, Inc.
Self‐navigated motion correction using moments of spatial projections in radial MRI
Authors: Welch Edward Brian , Rossman Phillip J. , Felmlee Joel P. , Manduca Armando 
Published: July 2004

AbstractInterest in radial MRI (also known as projection reconstruction (PR) MRI) has increased recently for uses such as fast scanning and undersampled acquisitions. Additionally, PR acquisitions offer intrinsic advantages over standard two‐dimensional Fourier transform (2DFT) imaging with respect to motion of the imaged object. It is well known that aligning each spatial domain projection's center of mass (calculated using the 0th and 1st moments) to the center of the field of view (FOV) corrects shifts caused by in‐plane translation. In this work, a previously unrealized ability to determine the in‐plane rotational motion of an imaged object using the 2nd moments of the spatial domain projections in conjunction with a specific projection angle acquisition time order is reported. We performed the correction using only the PR data itself acquired with the newly proposed projection angle acquisition time order. With the proposed view angle acquisition order, the acquisition is “self‐navigating” with respect to both in‐plane translation and rotation. We reconstructed the images using the aligned projections and detected acquisition angles to significantly reduce image artifacts due to such motion. The theory of the correction technique is described, and its effectiveness is demonstrated in phantom and in vivo experiments. Magn Reson Med 52:337–345, 2004. © 2004 Wiley‐Liss, Inc.
Echo‐planar BOLD fMRI of mice on a narrow‐bore 9.4 T magnet
Authors: Nair Govind , Duong Timothy Q. 
Published: July 2004

AbstractThe feasibility of BOLD fMRI in association with electrical somatosensory stimulation on spontaneously breathing, isoflurane‐anesthetized mice was investigated using spin‐echo, echo‐planar imaging (EPI) on a vertical narrow‐bore 9.4 T magnet. Three experiments were performed to derive an optimal fMRI protocol. In Experiment 1 (n = 9), spin‐echo BOLD responses to 10% CO2 challenge under graded isoflurane (0.25–1.25%) ranged from 10 ± 2% to 3.5 ± 0.9%; the optimal BOLD contrast‐to‐noise ratio peaked at 0.75% isoflurane. In Experiment 2 (n = 6), hindpaw somatosensory stimulations using 1–7 mA under 0.75% isoflurane revealed the optimal BOLD response was at 6 mA. In Experiment 3 (n = 5), BOLD responses to 4 and 6 mA stimulation under 0.75% and 1% isoflurane were evaluated in detail, confirming the optimal conditions in Experiment 2. These results demonstrated that BOLD fMRI using single‐shot, spin‐echo EPI in a mouse somatosensory stimulation model could be routinely performed on high‐field, vertical, narrow‐bore magnets. This protocol might prove useful for fMRI studies of transgenic mice. Magn Reson Med 52:430–434, 2004. © 2004 Wiley‐Liss, Inc.
Rapid T2 estimation with phase‐cycled variable nutation steady‐state free precession
Authors: Deoni Sean C.L. , Ward Heidi A. , Peters Terry M. , Rutt Brian K. 
Published: July 2004

AbstractVariable nutation SSFP (DESPOT2) permits rapid, high‐resolution determination of the transverse (T2) relaxation constant. A limitation of DESPOT2, however, is the presence of T2 voids due to off‐resonance banding artifacts associated with SSFP images. These artifacts typically occur in images acquired with long repetition times (TR) in the presence of B0 inhomogeneities, or near areas of magnetic susceptibility difference, such that the transverse magnetization experiences a net phase shift during the TR interval. This places constraints on the maximum spatial resolution that can be achieved without artifact. Here, a novel implementation of DESPOT2 is presented incorporating RF phase‐cycling which acts to shift the spatial location of the bands, allowing reconstruction of a single, reduced artifact‐image. The method is demonstrated in vivo with the acquisition of a 0.34 mm3 isotropic resolution T2 map of the brain with high precision and accuracy and significantly reduced artifact. Magn Reson Med 52:435–439, 2004. © 2004 Wiley‐Liss, Inc.
Prebolus quantitative MR heart perfusion imaging
Authors: Köstler Herbert , Ritter Christian , Lipp Michael , Beer Meinrad , Hahn Dietbert , Sandstede Jörn 
Published: July 2004

AbstractThe purpose of this study was to present the prebolus technique for quantitative multislice myocardial perfusion imaging. In quantitative MR perfusion studies the maximum contrast agent dose is limited by the requirement to determine the arterial input function (AIF). The prebolus technique consists of two consecutive contrast agent administrations. The AIF is determined from a first low‐dose bolus, while a second, high‐dose bolus allows the measurement of the myocardium with improved signal increase. The results of the prebolus technique using a multislice saturation recovery trueFISP sequence in healthy volunteers are presented. In comparison to a standard dose of 3 ml Gd‐DTPA, perfusion values are maintained while the signal increase in the concentration time courses was considerably improved, accompanied by reduced standard deviations of the obtained perfusion values (0.72 ± 0.13 ml/g/min for 1 ml/8 ml and 0.67 ± 0.10 ml/g/min for 1 ml/12 ml Gd‐DTPA, respectively). Magn Reson Med 52:296–299, 2004. © 2004 Wiley‐Liss, Inc.
Microcirculation and microvasculature in breast tumors: Pharmacokinetic analysis of dynamic MR image series
Authors: Brix Gunnar , Kiessling Fabian , Lucht Robert , Darai Susanne , Wasser Klaus , Delorme Stefan , Griebel Jürgen 
Published: July 2004

AbstractThe purpose of this study was to quantify microcirculation and microvasculature in breast lesions by pharmacokinetic analysis of Gd‐DTPA‐enhanced MRI series. StronglyT1‐weighted MR images were acquired in 18 patients with breast lesions using a saturation‐recovery‐TurboFLASH sequence. Concentration‐time courses were determined for blood, pectoral muscle, and breast masses and subsequently analyzed by a two‐compartment model to estimate plasma flow and the capillary transfer coefficient per unit of plasma volume (F/VP,KPS/VP) as well as fractional volumes of the plasma and interstitial space (fP,fI). Tissue parameters determined for pectoral muscle (fP= 0.04 ± 0.01,fI= 0.09 ± 0.01,F/VP= 2.4 ± 1.3 min‐1, andKPS/VP= 1.2 ± 0.5 min‐1) and 10 histologically proven carcinomas (fP= 0.20 ± 0.07,fI= 0.34 ± 0.16,F/VP= 2.4 ± 0.7 min‐1, andKPS/VP= 0.86 ± 0.62 min‐1) agreed reasonable well with literature data. Best separation between malignant and benign lesions was obtained by the ratioKPS/F(0.35 ± 0.17 vs. 1.23 ± 0.65). The functional imaging technique presented appears promising to quantitatively characterize tumor pathophysiology. Its impact on diagnosis and therapy management of breast tumors, however, has to be evaluated in larger patient studies. Magn Reson Med 52:420–429, 2004. © 2004 Wiley‐Liss, Inc.
Non‐Fourier‐encoded parallel MRI using multiple receiver coils
Authors: Mitsouras Dimitris , Hoge W. Scott , Rybicki Frank J. , Kyriakos Walid E. , Edelman Alan , Zientara Gary P. 
Published: July 2004

AbstractThis paper describes a general theoretical framework that combines non‐Fourier (NF) spatially‐encoded MRI with multichannel acquisition parallel MRI. The two spatial‐encoding mechanisms are physically and analytically separable, which allows NF encoding to be expressed as complementary to the inherent encoding imposed by RF receiver coil sensitivities. Consequently, the number of NF spatial‐encoding steps necessary to fully encode an FOV is reduced. Furthermore, by casting the FOV reduction of parallel imaging techniques as a dimensionality reduction of the k‐space that is NF‐encoded, one can obtain a speed‐up of each digital NF spatial excitation in addition to accelerated imaging. Images acquired at speed‐up factors of 2× to 8× with a four‐element RF receiver coil array demonstrate the utility of this framework and the efficiency afforded by it. Magn Reson Med 52:321–328, 2004. © 2004 Wiley‐Liss, Inc.
Imaging of myocardial infarction for diagnosis and intervention using real‐time interactive MRI without ECG‐gating or breath‐holding
Authors: Guttman Michael A. , Dick Alexander J. , Raman Venkatesh K. , Arai Andrew E. , Lederman Robert J. , McVeigh Elliot R. 
Published: July 2004

AbstractCurrent methods for MRI of infarcted myocardium require ECG‐gating and breath‐holding during contrast‐enhanced segmented k‐space inversion‐recovery (IR) imaging. However, ECG‐gating can be problematic in MRI, and breath‐holding can be difficult for some patients. This work demonstrates that infarcted tissue can be visualized without ECG‐gating or breath‐holding with the use of intermittent inversion pulses during real‐time (RT) interactive imaging with steady‐state free precession (SSFP). The sequence generates a RT image stream containing a myocardium‐nulled image every few frames, which allows nearly simultaneous observation of both infarcted regions and wall motion. First‐pass perfusion and wall motion can be simultaneously observed with minor parameter modifications. This method may reduce diagnostic scan time, expand the target population, improve patient comfort, and facilitate targeted, interventional treatment of infarcted myocardium. Supplementary material for this article can be found on the MRM website at http://www.interscience.wiley.com/jpages/0740‐3194/suppmat/index.html.Magn Reson Med 52:354–361, 2004. Published 2004 Wiley‐Liss, Inc.
MOCVD as a dry deposition method of ZnSe buffers for Cu(In,Ga)(S,Se)2 solar cells
Authors: Siebentritt Susanne , Walk Philipp , Fiedeler Ulrich , Lauermann Iver , Rahne Kari , Lux‐Steiner Martha Ch. , Niesen Thomas P. , Karg Franz 
Published: July 2004

AbstractZnSe prepared by metal organic chemical vapor deposition is used as a buffer layer in Cu(In,Ga)(S,Se)2 solar cells without any utilization of wet chemistry. Cell efficiencies are as good as cells with the conventional CdS buffer. Stability of unencapsulated cells under damp heat conditions is somewhat lower for the alternative buffer. The first stages of photoassisted growth are studied. X‐ray photoemission spectroscopy shows that a continuous layer is formed. Copyright © 2004 John Wiley & Sons, Ltd.
Spatially resolved evaluation of power losses in industrial solar cells by illuminated lock‐in thermography
Authors: Isenberg Joerg , Warta Wilhelm 
Published: July 2004

AbstractThe principles of a recently introduced measurement technique for power losses in solar cells, illuminated lock‐in thermography (ILT), are reviewed. The main advantage of ILT over dark lock‐in Thermography (DLT) is measurement under realistic operational conditions of solar cells. The main focus of this paper is to demonstrate the wide range of applications of ILT in identifying the causes of power losses in solar cells. For this purpose different evaluation methods are presented. A method for the evaluation of improvement potentials within a given cell technology is demonstrated. It is shown that different types of series resistance may be localized. Small areas of recombination losses (e.g., grain boundaries) can routinely be detected, which is not possible in dark lock‐in thermography. Good correspondence with light‐beam‐induced current images is found. A realistic evaluation of the impact of recombination losses on solar cell performance is demonstrated on two examples. Finally, process‐ or treatment‐induced recombination losses are investigated. In summary ILT is shown to be an extremely powerful tool in localizing, identifying and quantifying power losses of solar cells under realistic illumination conditions. Copyright © 2004 John Wiley & Sons, Ltd.
A method for the rapid depletion of albumin and immunoglobulin from human plasma
Authors: Greenough Carrie , Jenkins Rosalind E. , Kitteringham Neil R. , Pirmohamed Munir , Park B. Kevin , Pennington Stephen R. 
Published: July 2004

AbstractIn studies of the plasma proteome, the high abundance of proteins such as albumin and immunoglobulin impedes the investigation of lower abundance proteins that may be more suitable as biomarkers of disease. We report the specific removal of 98% of albumin and 80% of immunoglobulin heavy chain from human plasma by affinity chromatography, and the subsequent improvement in the number of spots detected and their resolution following two‐dimensional gel electrophoresis.
Proteome analysis of human mesothelial cells during epithelial to mesenchymal transitions induced by shed menstrual effluent
Authors: Demir Ayşe Y. , Demol Hans , Puype Magda , de Goeij Anton F. P. M. , Dunselman Gerard A. J. , Herrler Andreas , Evers Johannes L. H. , Vandekerckhove Joël , Groothuis Patrick G. 
Published: July 2004

AbstractPeritoneal endometriosis is the result of ectopic implantation and growth of endometrium tissue that has been regurgitated into the abdominal cavity during menstruation. We have previously shown that menstrual effluent induces epithelial to mesenchymal transitions (EMT) in mesothelial cells, which results in cell retraction and exposure of submesothelial extracellular matrix. Since endometrial tissue preferentially adheres to the extracellular matrix, adhesion of endometrial tissue to the peritoneum is facilitated. The EMT were shown to be associated with differential expression and phosphorylation of mesothelial proteins. Using radiolabeling and proteomics we detected changes in protein expression and phosphorylation that occur in mesothelial cells during the EMT process. The identity of 73 proteins, which were obtained from 324 analyzed spots, was confirmed. The expression of 35 proteins involved in organization of the cytoskeleton, signal transduction, regulation of the redox state, and production of ATP, was altered during the EMT process. Four of the identified proteins were differentially phosphorylated: annexin‐1, an actin‐binding protein and a substrate for receptor tyrosine kinases; tropomyosin‐α, a regulator of actin filament stability and cell shape; elongation factor 1 delta; ATP synthase β‐chain. In conclusion, factors from menstrual effluent induce specific changes in the expression and phosphorylation status of structural, regulatory and metabolic proteins relevant to the complex process of EMT in mesothelial cells.
Identification of protein targets for mycophenolic acid acyl glucuronide in rat liver and colon tissue
Authors: Shipkova Maria , Beck Hermann , Voland Antje , Armstrong Victor W. , Gröne Hermann‐Josef , Oellerich Michael , Wieland Eberhard 
Published: July 2004

AbstractCovalent binding of acyl glucuronides to proteins is considered an initiating event for the organ toxicity of drugs containing a carboxylic acid group. An acyl glucuronide (AcMPAG) of the immunosuppressant mycophenolic acid was described and shown to form covalent adducts with plasma albumin in vivo. The aim of the present investigation was to identify AcMPAG target proteins in the liver and colon of rats treated with mycophenolate mofetil, which may contribute to a better understanding of the mechanisms responsible for the development of side effects during therapy with this drug. Mycophenolate mofetil was administered per os in to Wistar rats (40 mg/kg/day) over 21 days. Proteins in liver and colon homogenates were separated by two‐dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. AcMPAG labeled protein spots were detected by Western blotting. After in‐gel tryptic digestion of the protein spots from parallel gels (n = 2), peptides were characterized by matrix‐assisted laser desorption/ionization‐time of flight‐mass spectrometry. Data base searching identified AcMPAG target proteins. Tryptic peptides with sufficient signal intensities were subjected to post‐source decay analysis. Three proteins in the liver (ATPase/ATP synthase (alpha and beta subunits), protein disulfide isomerase A3 and selenium binding protein) and one protein in the colon (selenium binding protein) were identified as targets for AcMPAG. ATPase/ATP synthase and protein disulfide isomerase are essential proteins involved in the control of the energy and redox state of the cells, whereas the physiological role of selenium binding protein is not fully understood. This study shows for the first time the formation of adducts between tissue proteins and AcMPAG. Whether this chemical modification is associated with compromised protein function and drug toxicity remains to be investigated.