bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of experimental parameters on high b‐value q‐space MR images of excised rat spinal cord
Authors: Nossin‐Manor Revital , Duvdevani Revital , Cohen Yoram 
Published: June 2005

AbstractThe influence of diffusion time (Δ), gradient duration (δ), and TE on the appearance of high b‐value q‐space diffusion MR images of excised rat spinal cord (SC) was evaluated. The water signal decays in the white (WM) and gray matter (GM) were analyzed when the diffusion was measured perpendicular (⟂) and parallel (‖) to the fibers of the SC, using three different approaches: single‐component q‐space analysis, the biexponential model, and the bi‐Gaussian fit of the displacement distribution profile. Probability and displacement contrast and anisotropy indices were calculated for the WM and GM. It was found that WM/GM contrast increases as the diffusion time is increased when diffusion is measured perpendicular to the long axis of the SC. At a diffusion time of 50 ms, when diffusion was measured parallel to the fibers of the SC, the displacement was found to be higher for GM as compared to WM. For this direction the WM/GM contrast increased when diffusion time was increased, although here the changes were much less pronounced than for the perpendicular direction. The WM/GM displacement contrast nearly disappears for a diffusion time of 150 ms, when diffusion is measured parallel to the fibers of the SC. As expected, the anisotropy indices were found to be higher in WM than in GM, and increased with the increase in diffusion time. Both δ and TE affected the extracted parameters. It was found that long δ and long TE overemphasizes the apparent slow‐diffusing water component of the SC, which is also the more restricted one. It is demonstrated that the single‐component q‐space analysis best describes diffusion in WM when diffusion is measured perpendicular to the fibers of the SC. In other cases, a more complete description is obtained by using two‐component models. Magn Reson Med 54:96–104, 2005. © 2005 Wiley‐Liss, Inc.
Generic method for imaging transgene expression
Authors: So Po‐Wah , Hotee Sarah , Herlihy Amy H. , Bell Jimmy D. 
Published: June 2005

AbstractWe propose a generic method to report on gene expression based on the use of an antigen–antibody reporting system and visualization by MRI. This methodology was demonstrated using a truncated form of the H2Kk antigen, tH2Kk, as the nonendogenous antigen to be imaged. HeLa cells, transfected to express tH2Kk, exposed to tH2Kk antibodies conjugated to a superparamagnetic iron oxide particle, generated strong negative contrast compared to non‐H2Kk expressing cells by MRI. T2 of the tH2Kk expressing cells was 57.6 ± 17.0 ms, compared to 424.0 ± 38.7 and 445.4 ± 47.2 ms for the mock transfected and nontransfected cells, respectively (P < 0.001). tH2Kk expression in the former cells was confirmed by flow cytometry, fluorescence, and electron microscopy. The methodology can be adapted to image in vivo other nonendogenous antigens in cells/tissues. Magn Reson Med 54:218–221, 2005. © 2005 Wiley‐Liss, Inc.
Metal artifacts caused by gradient switching
Authors: Graf Hansjörg , Steidle Günter , Martirosian Petros , Lauer Ulrike A. , Schick Fritz 
Published: June 2005

AbstractIn metal parts, e.g., implants or instruments, eddy currents can be induced from gradient switching if positioned off‐center inside the MR scanner. For the first time, a systematic analysis of related artifacts was performed. Current strength increases in conjunction with increasing size of the part, increasing electrical conductivity, distance from isocenter, and increasing gradient strengths. A xy‐plane oriented copper ring (do = 20 mm, di = 15 mm, 2 mm thick) was examined at isocenter and at x = 15 cm, y = z = 0. Comparisons of xy‐, xz‐, and yz‐slices, recorded for both possibilities to select encoding directions, revealed effects from ramp‐down of the slice‐selection and ramp‐up of the read‐out gradient. Near the metal part, temporary inhomogeneities were superimposed to the static field and spin‐dephasing signal loss resulted, despite using spin‐echo technique. Artifacts depended on excitation and read‐out bandwidth. For an equivalent titanium ring, conductivity related effects could not be ascertained but distinct susceptibility effects occurred. MR compatibility of implants/instruments therefore requires both low susceptibility and low conductivity. Magn Reson Med 54:231–234, 2005. © 2005 Wiley‐Liss, Inc.
Analysis and compensation of eddy currents in balanced SSFP
Authors: Bieri O. , Markl M. , Scheffler K. 
Published: June 2005

AbstractBalanced steady‐state free precession (SSFP) completely compensates for all gradients within each repetition time (TR), and is thus very sensitive to any magnetic field imperfection that disturbs the perfectly balanced acquisition scheme. It is demonstrated that balanced SSFP is especially sensitive to changing eddy currents that are induced by stepwise changing phase‐encoding (PE) gradients. In contrast to the linear k‐space trajectory, which has small variations between consecutive encoding steps, other encoding schemes (e.g., centric, random, or segmented orderings) exhibit significant jumps in k‐space between adjacent PE steps, and consequently induce rapidly changing eddy currents. The resulting disturbances induce significant image artifacts, such that compensation strategies are essential when nonlinear PE schemes are applied. Although direct annihilation of the induced eddy currents by additional, opposing magnetic fields has been investigated, it is limited by uncertainty regarding the time evolution of induced eddy currents. A generic (and thus system‐unrelated) compensation strategy is proposed that consists of “pairing” of consecutive PE steps. Another approach is based on partial dephasing along the slice direction that annihilates eddy‐current‐induced signal oscillations. Both pairing of the PE steps and “through‐slice equilibration” are easy to implement and allow the use of arbitrary k‐space trajectories for balanced SSFP. Magn Reson Med 54:129–137, 2005. © 2005 Wiley‐Liss, Inc.
Suppression of lipid artifacts in amide proton transfer imaging
Authors: Sun Phillip Zhe , Zhou Jinyuan , Sun Weiyun , Huang Judy , van Zijl Peter C. M. 
Published: June 2005

AbstractAmide proton transfer (APT) imaging is a type of chemical exchange saturation transfer imaging in which the amide protons of cellular proteins and peptides are saturated and detected via the water resonance. To study this effect, conventional magnetization transfer and direct saturation effects in the frequency‐dependent water saturation spectrum (z‐spectrum) need to be removed by asymmetry analysis with respect to the water frequency offset. When using echo planar imaging, it was found that unequal pericranial fat saturation at equidistant higher and lower frequencies with respect to water leads to a lipid artifact in APT asymmetry images. It is demonstrated that a chemical‐shift‐selective refocusing pulse in combination with crusher gradients can suppress this artifact and provide high‐quality images. Magn Reson Med 54:222–225, 2005. © 2005 Wiley‐Liss, Inc.
MRI detection of macrophage activity after experimental stroke in rats: New indicators for late appearance of vascular degradation?
Authors: Weber Ralph , Wegener Susanne , Ramos‐Cabrer Pedro , Wiedermann Dirk , Hoehn Mathias 
Published: June 2005

AbstractFocal cerebral ischemia was induced in rats and followed with high‐resolution MRI methods for a chronic period of 10 weeks. Two weeks after stroke induction and at the end of the observation period, conventional histological analysis was combined with immunohistochemical staining for macrophages and with Prussian blue staining for the detection of ferric iron. In the late chronic phase, a patchy hypointensity was observed in the ischemic caudoputamen exclusively on T‐weighted (TW) images, with no change in quantitative T1 and T2 relaxation time maps. This characteristic MRI pattern is different from hemorrhagic transformations (HTs) at earlier time points (2 weeks post stroke induction), which became apparent on images of all three imaging sequences. The exclusive T‐sensitive hypointensity colocalized with iron‐positive macrophages in the lesion territory at this time. These iron‐containing macrophages were found predominantly around blood vessels in the ischemic tissue, and interpreted as the result of a phagocytotic incorporation of red blood cells leaking from slowly degrading vessels. The present investigation demonstrates the sensitivity of heavily TW 3D MRI for observing the inflammatory response in the chronic phase after stroke, without prior systemic labeling of the blood‐borne macrophages by iron oxide nanoparticles. Magn Reson Med 54:59–66, 2005. © 2005 Wiley‐Liss, Inc.
Optimization of 3D contrast‐enhanced pulmonary magnetic resonance angiography in pediatric patients with congenital heart disease
Authors: Macgowan Christopher K. , Al‐Kwifi Osama , Varodayan Florence , Yoo Shi‐Joon , Wright Graham A. , Kellenberger Christian J. 
Published: June 2005

AbstractContrast kinetics were studied in the main pulmonary artery (MPA) and ascending aorta (AAo) of 12 children with congenital heart disease. This information was used to optimize the timing of data acquisition for contrast‐enhanced MR angiography in these vessels. To reduce contrast‐agent dosage in these fragile patients, contrast enhancement was measured during routine diagnostic 3D magnetic resonance (MR) angiography instead of using test‐bolus methods. This was possible by acquiring 2D cross‐sectional images of the MPA and AAo during the 3D scan. Time‐to‐peak in the MPA and AAo was 4.9 ± 2.2 and 6.1 ± 2.2 s, respectively, while the transit time between the two vessels was 4.5 ± 0.6 s. A point‐spread‐function analysis showed that intravascular signal strength was maximized if data acquisition began 4.7 ± 2.3 s after the first arrival of contrast in the MPA and 5.6 ± 2.3 s in the AAo. Little signal loss and artifact resulted when longer acquisition delays were used because contrast‐agent clearance was slow. Based on these results, MR angiography of both the MPA and the AAo in children with congenital heart disease can be performed using elliptic‐centric k‐space sampling and a trigger delay of 7.9 s after contrast arrival in the AAo (i.e., time‐to‐peak signal strength in the AAo plus one SD to account for intersubject variability). Magn Reson Med 54:207–212, 2005. © 2005 Wiley‐Liss, Inc.
Transmission line for improved RF safety of interventional devices
Authors: Weiss Steffen , Vernickel Peter , Schaeffter Tobias , Schulz Volkmar , Gleich Bernhard 
Published: June 2005

AbstractA new concept is proposed to improve the safety of transmission lines with respect to heating during RF transmission. It is based on the integration of transformers into the transmission line. The concept was applied to an active tracking device. Miniature transformers were designed, and two types of tracking devices were built based on a standard line and a transformer line. Temperature measurements were performed for both devices during high specific absorption rate (SAR) scanning, and the suppression of RF heating to a physiologically non‐relevant level was demonstrated for the transformer device. The transmission properties of the transformer line were examined in simulations and RF measurements. Active tracking with the transformer device performed robustly in the phantom. Because of the favorable signal transmission properties of the tested device, it is expected that the concept can be applied to the construction of clinical devices for tracking and intravascular imaging, which are RF‐safe under clinical SAR conditions. Since the transformer line has a large bandwidth, the concept may also be applied for RF‐safe transmission of non‐MR signals. Magn Reson Med 54:182–189, 2005. © 2005 Wiley‐Liss, Inc.
Measurement of cerebrospinal fluid oxygen partial pressure in humans using MRI
Authors: Zaharchuk Greg , Martin Alastair J. , Rosenthal Guy , Manley Geoffery T. , Dillon William P. 
Published: June 2005

AbstractFluid‐attenuated inversion recovery (FLAIR) images obtained during the administration of supplemental oxygen demonstrate a hyperintense signal within the cerebrospinal fluid (CSF) that is likely caused by T1 changes induced by paramagnetic molecular oxygen. Previous studies demonstrated a linear relationship between the longitudinal relaxation rate (R1 = 1/T1) and oxygen content, which permits quantification of the CSF oxygen partial pressure (PcsfO2). In the current study, CSF T1 was measured at 1.5 T in the lateral ventricles, third ventricle, cortical sulci, and basilar cisterns of eight normal subjects breathing room air or 100% oxygen. Phantom studies performed with artificial CSF enabled absolute PcsfO2 quantitation. Regional PcsfO2 differences on room air were observed, from 65 ± 27 mmHg in the basilar cisterns to 130 ± 49 mmHg in the third ventricle. During 100% oxygen, PcsfO2 increases of 155 ± 45 and 124 ± 34 mmHg were measured in the basilar cisterns and cortical sulci, respectively, with no change observed in the lateral or third ventricles. PcsfO2 measurements in humans breathing room air or 100% oxygen using a T1 method are comparable to results from invasive human and animal studies. Similar approaches could be applied to noninvasively monitor oxygenation in many acellular, low‐protein body fluids. Magn Reson Med 54:113–121, 2005. © 2005 Wiley‐Liss, Inc.
Eight‐channel phased array coil and detunable TEM volume coil for 7 T brain imaging
Authors: Wiggins G. C. , Potthast A. , Triantafyllou C. , Wiggins C. J. , Wald L. L. 
Published: June 2005

AbstractAn eight‐channel receive‐only brain coil and table‐top detunable volume transmit coil were developed and tested at 7 T for human imaging. Optimization of this device required attention to sources of interaction between the array elements, between the transmit and receive coils and minimization of common mode currents on the coaxial cables. Circular receive coils (85 mm dia.) were designed on a flexible former to fit tightly around the head and within a 270‐mm diameter TEM transmit volume coil. In the near cortex, the array provided a fivefold increase in SNR compared to a TEM transmit‐receive coil, a gain larger than that seen in comparable coils at 3 T. The higher SNR gain is likely due to strong dielectric effects, which cause the volume coil to perform poorly in the cortex compared to centrally. The sensitivity and coverage of the array is demonstrated with high‐resolution images of the brain cortex. Magn Reson Med 54:235–240, 2005. © 2005 Wiley‐Liss, Inc.
New method for the simultaneous detection of metabolites and water in localized in vivo 1H nuclear magnetic resonance spectroscopy
Authors: Dreher Wolfgang , Leibfritz Dieter 
Published: June 2005

AbstractA new two‐scan method for localized 1H in vivo NMR spectroscopy (MRS) without water suppression (WS) is described. In one of the scans, two chemical shift selective 180° pulses are applied prior to a standard localization sequence to invert all metabolite signals upfield and downfield from water, which remains unaffected. The difference spectrum records the metabolites whereas water and accompanying gradient induced artifacts are widely suppressed. The method was implemented on a 4.7‐T system using point resolved spectroscopy with a short echo time of 18 ms. Phantom measurements proved the feasibility of absolute quantification using water as an internal reference. Measurements on healthy rat brain yielded comparable spectrum quality as measurements with water presaturation. The method does not require additional adjustments or sophisticated data postprocessing and scales favorably with increasing B0 field. Therefore, the method should be useful for 1H MRS without WS. Although the two‐step method doubles the minimum total measurement time, it may also be of interest for spectroscopic imaging (SI) without WS, in particular if fast SI techniques are applied. Magn Reson Med 54:190–195, 2005. © 2005 Wiley‐Liss, Inc.
Magnetization transfer weighted imaging in the upper cervical spinal cord using cerebrospinal fluid as intersubject normalization reference (MTCSF imaging)
Authors: Smith Seth A. , Xavier Golay , Ali Fatemi , Craig K. Jones , Gerald V. Raymond , Hugo W. Moser , Peter C. M. van Zijl 
Published: June 2005

AbstractThe magnetization transfer ratio (MTR) is a reliable measure of MT effects because it employs an internal standard that allows quantitative comparison between subjects, independent of other contrasts, coil loading, and coil sensitivity profiles. However, at very high spatial resolution in the spinal cord at 1.5 T, the use of MTR quantification has been hampered by low signal‐to‐noise ratio (SNR) and acute sensitivity to motion. Here, the suitability of cerebrospinal fluid (CSF) as an alternative inter‐subject MT signal intensity reference for the spine is evaluated. Contrary to MTR, this so‐called MTCSF internal standard does not remove interfering T1, T2, and spin density contrast and is not expected to be able to discriminate between myelination and inflammation effects. However, it can detect initial changes in myelination when signal alterations are not yet detectable by conventional MRI. As a first example, this is demonstrated for the noninflammatory spinal cord white matter disease adrenomyeloneuropathy. Magn Reson Med 54:201–206, 2005. © 2005 Wiley‐Liss, Inc.
The smoothing effect of a simultaneous directions parallel method as applied to Poisson problems
Authors: Galo José R. , Calzada M. Carmen , Cruz José L. , Marín Mercedes , Albarreal I. Ignacio , Fernández‐Cara Enrique 
Published: June 2005

AbstractBy using local Fourier analysis, a simultaneous directions parallel method, which is a particular instance of the parallel fractional step algorithm, is shown to possess smoothing effects when applied to Poisson problems. The specific smoothing factor is determined and the expected factor values are found to be consistent with those obtained. The simultaneous directions approach is an advantageous alternative to other existing smoothers in the multigrid environment. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006
New π‐stacked benzofulvene polymer showing thermoreversible polymerization: Studies in macromolecular and aggregate structures and polymerization mechanism
Authors: Cappelli Andrea , Anzini Maurizio , Vomero Salvatore , Donati Alessandro , Zetta Lucia , Mendichi Raniero , Casolaro Mario , Lupetti Pietro , Salvatici Paolo , Giorgi Gianluca 
Published: June 2005

AbstractThe macromolecular and aggregate structures of poly[ethyl 1‐methylene‐3‐(4‐methylphenyl)‐1H‐indene‐2‐carboxylate] (poly‐BF1; a new polymer based on a functionalized benzofulvene moiety showing interesting properties, i.e., thermoreversible polymerization/depolymerization behavior, high solubility in the most common organic solvents, and susceptibility to molecular manipulation) have been investigated with NMR spectroscopy, absorption and emission spectrophotometry, and transmission electron microscopy (TEM). Moreover, the polymerization mechanism has been studied to obtain further information on the polymer structure. The collected evidence is consistent in indicating for poly‐BF1 a vinyl (1,2) polymer structure stabilized by means of aromatic stacking interactions. Furthermore, TEM studies performed on metal replicas have shown that the polymer is liable to give nanostructured aggregates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3289–3304, 2005
Fluorescein–formaldehyde oligomeric pH indicator: Facile synthesis, characterization, and potential application
Authors: Liu Zhihong , Gao Shuyu , Chen Tianlu 
Published: June 2005

AbstractA kind of fluorescent oligomeric pH indicator (fluorescein–formaldehyde product) was synthesized by the reaction of fluorescein with formaldehyde under alkaline conditions by a one‐pot method. The synthesized product was fully characterized with Fourier transform infrared, 1H NMR, ultraviolet–visible spectra, luminescence spectra, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra. The results indicated that the reaction was a typical phenol–formaldehyde reaction and that the fluorescein–formaldehyde product contained dimer, trimer, tetramer, and even a little octamer. Visible spectra and luminescence spectra showed that the fluorescein–formaldehyde product could still provide pH sensitivity similar to that of fluorescein. In addition, the oligomeric pH indicator immobilized poly(vinyl alcohol) membranes could be easily fabricated and achieved better long‐term stability and fast equilibrium response. Thus, they are promising transparent membranes for optical pH sensors of a wide pH range (0.0–10.0) based on absorption and fluorescence. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3447–3453, 2005
Primary therapy of carcinoma of the large bowel
Authors: Fazio Victor W. , Tjandra Joe J. 
Published: June 2005

AbstractMost colonic and rectal carcinomas are treated by excision, usually with the object of cure. Adequate and safe resection depends upon sound understanding of the anatomy and pathology of the tumor. The surgical options in various clinical situations are discussed but the final choice has to be individualized. Improved understanding of the biology of large bowel cancer and the advent of circular stapling devices have significantly altered the surgical practice in large bowel cancer. Despite these innovative advances, there has only been a modest improvement in survival over the last few decades. This is because the concept of “sequential tumor spread” does not always hold true. Systemic adjuvant therapy that is effective and safe is needed for selected patients. Notwithstanding, surgical resection remains the most effective therapy for large bowel cancer.
Adjuvant therapy for colorectal carcinoma
Authors: Metzger U. 
Published: June 2005

AbstractIn Western industrialized countries, colorectal adenocarcinoma is the second most common solid malignant tumor. Despite radical surgery in 75% to 80% of all cases, about 50% of patients with colorectal carcinoma die of this tumor. The essential advances of the last years are the reduction in the surgical complication rate and postoperative mortality. Recent studies show that radiotherapy for rectal carcinoma and chemotherapy (5‐Fluorouracil in combination with levamisole) for colon carcinoma as additional measures in certain subgroups can significantly improve results. However, such multimodality treatment concepts need adequate equipment and experience and should only be implemented, whenever possible, in controlled clinical trials.
Follow‐up plans after treatment of primary colon and rectum cancer
Authors: Steele Glenn 
Published: June 2005

AbstractAlthough some would argue about the value of routine follow‐up of patients with colon and rectal cancer, well designed programs of testing have been shown to identify treatable recurrence at its earliest detectable stage. Treatment of these recurrences appears to be associated with improved survival. Newer applications of radiolabeled antibodies that are directed to specific or nonspecific cell surface epitopes may increase the value of serologic tumor markers. Ultimately, the application of progressively more stringent cost controls in our medical care delivery systems will demand that follow‐up tests be proven of value either in a curative or palliative sense to the patient with recurrent disease.
Prevention and management of recurrent rectal cancer
Authors: Beart Robert W. 
Published: June 2005

AbstractIncreased attention to surgical indications and technique can minimize the risks of recurrent rectal cancer. In addition, the use of adjuvant chemoradiation therapy has been shown to further decrease the risks of recurrent rectal cancer. In the event a recurrence develops, surgical therapy, combined with radiation therapy, can result in local control in as many as 75% of patients and long term survival in 25% to 40% of patients.