bluuebunny/crossref_metadata_2025 huggingface dataset:
An analytical solution for the SSFP signal in MRI
Authors: Hänicke Wolfgang , Vogel Horst U.
Published: March 2003

Among previous analyses of the steady‐state free‐precession (SSFP) signal in rapid MRI, one treatment resulted in equations that require the evaluation of infinite binomial series. Here, an analytical solution is derived by a transformation into the power series expansion of the derivative of the inverse sine function, which is essentially a root. The treatment is extended to include higher‐order signals. The results demonstrate the identity of the vastly different equations for the SSFP signals reported so far. Applications consist of the derivation of closed expressions for the signal in echo‐shifted MRI and a corresponding analysis of TrueFISP sequences. Magn Reson Med 49:771–775, 2003. © 2003 Wiley‐Liss, Inc.
Is multicomponent T2 a good measure of myelin content in peripheral nerve?
Authors: Webb Stephanie , Munro Catherine A. , Midha Rajiv , Stanisz Greg J.
Published: March 2003

Multicomponent T2 relaxation of normal and injured rat sciatic nerve was measured. The T2 relaxation was multiexponential, indicating the multicompartmental nature of T2 decay in nerve tissue. The size of the short, observed T2 component correlated very well with quantitative assessment of myelin using computer‐assisted histopathological image analysis of myelin. Specifically, the size of the short T2 component reflected the processes of myelin loss and remyelination accompanying Wallerian degeneration and regeneration following trauma. However, it represented all myelin present in the sample and did not distinguish between intact myelin and myelin debris. Other changes in T2 spectra were also observed and could be correlated with axonal loss and inflammation. The study also questions the validity of previously offered interpretations of T2 spectra of nerve. Magn Reson Med 49:638–645, 2003. © 2003 Wiley‐Liss, Inc.
Muscle glycogenolysis is not activated by changes in cytosolic P‐metabolites: A 31P and 1H MRS demonstration
Authors: Hsu Alex C. , Dawson M. Joan
Published: March 2003

Skeletal muscle contraction and glycogenolysis are closely coupled. The standard explanation for this coupling, as taught in modern biochemistry textbooks, is that the metabolic products of contraction (ADP, AMP, Pi) feed back to activate glycogenolytic enzymes, thus providing for resynthesis of ATP. However, both in vivo 31P MRS analyses and chemical analyses of muscle extracts have provided results that are contrary to this theory, at least in its simplest form. The MRS studies suffer from ambiguous assumptions. More importantly, in 31P MRS studies the dependent and independent variables are often confounded because the glycogenolytic rate is calculated from the same data which are used to calculate the other metabolic variables. The analysis of biopsies has been necessarily quite limited, and suffers from a different set of experimental artifacts. Thus, the problem of contraction‐glycogenolysis‐coupling was reassessed using a quantitatively accurate 1H MRS method. It is confirmed that glycogenolysis and contractions are closely coupled during repetitive exercise, while glycogenolysis and P‐metabolite concentrations are not. A simple metabolic feedback system cannot explain contraction‐glycogenolysis‐coupling. Magn Reson Med 49:626–631, 2003. © 2003 Wiley‐Liss, Inc.
Indirect imaging of ethanol via magnetization transfer at high and low magnetic fields
Authors: Estilaei Mohammad R. , Matson Gerald B. , Meyerhoff Dieter J.
Published: March 2003

Ethanol (EtOH) is believed to exert its neurochemical effects through interactions with brain cellular components, which causes a fraction of brain EtOH to have a lower molecular mobility. This facilitates magnetization transfer to other molecules similarly associated with macromolecules, such as water. It was hypothesized that this effect can be used in vivo to image EtOH indirectly via the much stronger brain tissue water resonance. EtOH‐containing bovine serum albumin samples were used to demonstrate magnetic coupling between EtOH and water at 7 T and 1.5 T. Spectroscopy and imaging experiments demonstrated that EtOH signal saturation yielded greater water signal reduction than inversion and that this reduction scaled with EtOH concentration in the BSA samples. In human brain at physiologically relevant brain EtOH concentrations, water signal reductions were measurable when saturating the EtOH resonance. Strengths and limitations of indirectly imaging brain EtOH are discussed. Magn Reson Med 49:755–759, 2003. © 2003 Wiley‐Liss, Inc.
Fast high‐resolution 3D segmented echo planar imaging for dose mapping using a superheated emulsion chamber
Authors: Lamba Michael , Holland Scott K. , Schmithorst Vincent , Dardzinski Bernard , d'Errico Francesco , Nath Ravinder
Published: March 2003

The superheated emulsion chamber (SEC) consists of superheated droplets of halocarbons in an aqueous gel. The gel resides in a pressure chamber. Brachytherapy sources can be implanted in the SEC for radiation dosimetry studies. Upon irradiation by ionizing radiation, the metastable droplets vaporize to form microbubbles. MRI can be used to determine the distribution of bubbles following irradiation of the SEC. In order to generate sufficient statistical accuracy in the determination of dose distributions around brachytherapy sources, it is necessary to use hundreds of irradiation cycles. Susceptibility‐weighted images provide contrast between the gel and the vapor microbubbles. This article describes a 3D, blipped, double‐sampled, segmented echo‐planar imaging technique for rapidly imaging the SEC at 650 μm isotropic 3D resolution in about 2 min. This method was used with a pressure cycling SEC to acquire hundreds of images in several hours. Results are presented showing the 2D dose distribution generated by an 125I source as measured in the SEC using this new imaging method. Magn Reson Med 49:675–681, 2003. © 2003 Wiley‐Liss, Inc.
Classification and quantification of neuronal fiber pathways using diffusion tensor MRI
Authors: Ding Zhaohua , Gore John C. , Anderson Adam W.
Published: March 2003

Quantitative characterization of neuronal fiber pathways in vivo is of significant neurological and clinical interest. Using the capability of MR diffusion tensor imaging to determine the local orientations of neuronal fibers, novel algorithms were developed to bundle neuronal fiber pathways reconstructed in vivo with diffusion tensor images and to quantify various physical and geometric properties of fiber bundles. The reliability of the algorithms was examined with reproducibility tests. Illustrative results show that consistent physical and geometric measurements of novel properties of neuronal tissue can be obtained, which offer considerable potential for the quantitative study of fiber pathways in vivo. Magn Reson Med 49:716–721, 2003. © 2003 Wiley‐Liss, Inc.
Detection of elevated glutathione in meningiomas by quantitative in vivo1H MRS
Authors: Opstad K.S. , Provencher S.W. , Bell B.A. , Griffiths J.R. , Howe F.A.
Published: March 2003

Glutathione has major roles in removing free radicals and toxins from normal tissues, but its presence in tumor cells hinders the effectiveness of many anticancer therapies. Analysis of short echo time brain tumor1H spectra at 1.5 T using a linear combination of metabolite spectra (LCModel) suggested a significant contribution of glutathione to meningioma spectra. By in vivo MRS (TE = 30 ms, TR = 2020 ms), reduced glutathione was found to be significantly elevated in meningiomas (3.3 ± 1.5 mM, Mann Whitney,P< 0.005) compared to normal white matter (1.2 ± 0.15 mM) and low‐grade gliomas (1.0 ± 0.26 mM), in agreement with published histofluorescence studies of tumor biopsies. Glx concentrations were also found to be elevated in meningiomas compared to astrocytomas or normal white matter, indicative of metabolic differences. The ability to noninvasively quantify reduced glutathione in vivo may aid selection of treatment therapies and also provide an indication of tumor aggressiveness. Magn Reson Med 49:632–637, 2003. © 2003 Wiley‐Liss, Inc.
Cell internalization of anionic maghemite nanoparticles: Quantitative effect on magnetic resonance imaging
Authors: Billotey C. , Wilhelm C. , Devaud M. , Bacri J.C. , Bittoun J. , Gazeau F.
Published: March 2003

Anionic iron oxide nanoparticles are efficiently internalized into macrophages where they concentrate within micrometric endosomes, conferring on them a high magnetic susceptibility. The uptake of anionic maghemite nanoparticles by macrophages was quantified by an electron spin resonance (ESR) experiment. MR spin‐echo sequences were performed with various TEs and TRs. The contrast enhancement was compared between two types of agarose phantoms with the same equivalent ferrite concentrations but containing either dispersed isolated nanoparticles or magnetically labeled macrophages. It is shown that the intracellular confinement of maghemite nanoparticles within micrometric endosomes results in a significant decrease of the longitudinal relaxivity and a moderate decrease of the transverse relaxivity compared to the relaxivities of the dispersed isolated nanoparticles. As a consequence, the signature of endosomal magnetic labeling consists of a negative contrast on T1‐weighted images in the whole ferrite concentration range, whereas the presence of extracellular isolated nanoparticles can result in a positive enhancement. Magn Reson Med 49:646–654, 2003. © 2003 Wiley‐Liss, Inc.
Novel T‐weighted contrast preparation scheme for segmented k‐space myocardial imaging
Authors: Redpath T.W. , Semple S.I.K. , Waiter G.D. , Frisch L. , Norton M.Y. , Morris D.M. , Egred M.
Published: March 2003

A novel T‐weighted contrast‐preparation scheme is described for use with segmented k‐space cardiac sequences. This approach frees the imaging phase from the requirement of a long TE and, hence, a relatively long TR. A [90°x‐τ‐90°ρ] preparation scheme is used to acquire four image data sets with the phase ρ of the second pulse set to x, y, –x, and –y. The ρ = x raw data is subtracted from the ρ = –x data to form the “x” image, with a similar subtraction to generate the “y” image. These images are added in quadrature to obtain the T‐weighted image. The method results in reduced artifact compared to a simple two‐image scheme with ρ = x, and y. T was measured in the myocardial septum in six normal volunteers by comparing τ = 7 and 28 ms images, and it was found to be 44 ± 5 ms at 0.95 T. Magn Reson Med 49:776–780, 2003. © 2003 Wiley‐Liss, Inc.
Capillarization of the sinusoids in liver fibrosis: Noninvasive assessment with contrast‐enhanced MRI in the rabbit
Authors: Van Beers Bernard E. , Materne Roland , Annet Laurence , Hermoye Laurent , Sempoux Christine , Peeters Frank , Smith Anne M. , Jamart Jacques , Horsmans Yves
Published: March 2003

Sinusoidal capillarization induces microcirculatory changes in liver cirrhosis and fibrosis. The purpose of this study was to assess whether contrast‐enhanced MRI can be used to demonstrate the effects of sinusoidal capillarization in liver fibrosis. Dynamic MRI after injection of a low‐molecular‐weight contrast agent of 0.56 kDa (Gd‐DOTA), and two high‐molecular‐weight contrast agents of 6.47 kDa and 52 kDa (P792 and P717) was performed in rabbits with liver fibrosis induced by cholesterol and diethylstilbestrol. The hepatic distribution volume accessible to the high‐molecular‐weight agents decreased in the rabbits with liver fibrosis (P792: 7.8% ± 1.7% vs. 10.1% ± 1.8% in normal rabbits, P = .038; P717: 6.2% ± 2.1% vs. 9.7% ± 1.6% in normal rabbits, P = .007), whereas the hepatic mean transit time (MTT) of the low‐molecular‐weight agent was increased (15.9 ± 8.0 s vs. 8.8 ± 2.6 s in normal rabbits, P = .015). In rabbits with liver fibrosis, the clearance of indocyanine green (ICG) was correlated with the volume accessible to the high‐molecular‐weight agents (P792: r = 0.810, P = .015; P717: r = 0.857, P = .007). The collagen content of the liver was inversely correlated with the distribution volume of P717 (r = –.833, P = .010) and with the ICG clearance (r = –.810, P = .015). It was concluded that the microcirculatory changes induced by sinusoidal capillarization in liver fibrosis can be demonstrated noninvasively with MRI. Magn Reson Med 49:692–699, 2003. © 2003 Wiley‐Liss, Inc.
On the transient phase of balanced SSFP sequences
Authors: Scheffler Klaus
Published: March 2003

The signal intensity of balanced steady‐state free precession (SSFP) imaging is a function of the proton density, T1, T2, flip angle (α), and repetition time (TR). The steady‐state signal intensity that is established after about 5*T1/TR can be described analytically. The transient phase or the approach of the echo amplitudes to the steady state is an exponential decay from the initial amplitude after the first excitation pulse to the steady‐state signal. An analytical expression of the decay rate of this transient phase is presented that is based on a simple analysis derived from the Bloch equations. The decay rate is a weighted average of the T1 and T2 relaxation times, where the weighting is determined by the flip angle of the excitation pulses. Thus, balanced SSFP imaging during the transient phase can provide various contrasts depending on the flip angle and the number of excitation pulses applied before the acquisition of the central k‐space line. In addition, transient imaging of hyperpolarized nuclei, such as 3He, 129Xe, or 13C, can be optimized according to their T1 and T2 relaxation times. Magn Reson Med 49:781–783, 2003. © 2003 Wiley‐Liss, Inc.
Steady‐state free precession with myocardial tagging: CSPAMM in a single breathhold
Authors: Zwanenburg Jaco J.M. , Kuijer Joost P.A. , Marcus J. Tim , Heethaar Robert M.
Published: March 2003

A method is presented that combines steady‐state free precession (SSFP) cine imaging with myocardial tagging. Before the tagging preparation at each ECG‐R wave, the steady‐state magnetization is stored as longitudinal magnetization by an α/2 flip‐back pulse. Imaging is continued immediately after tagging preparation, using linearly increasing startup angles (LISA) with a rampup over 10 pulses. Interleaved segmented k‐space ordering is used to prevent artifacts from the increasing signal during the LISA rampup. First, this LISA‐SSFP method was evaluated regarding ghost artifacts from the steady‐state interruption by comparing LISA with an α/2 startup method. Next, LISA‐SSFP was compared with spoiled gradient echo (SGRE) imaging, regarding tag contrast‐to‐noise ratio and tag persistence. The measurements were performed in phantoms and in six subjects applying breathhold cine imaging with tagging (temporal resolution 51 ms). The results show that ghost artifacts are negligible for the LISA method. Compared to the SGRE reference, LISA‐SSFP was two times faster, with a slightly better tag contrast‐to‐noise. Additionally, the tags persisted 126 ms longer with LISA‐SSFP than with SGRE imaging. The high efficiency of LISA‐SSFP enables the acquisition of complementary tagged (CSPAMM) images in a single breathhold. Magn Reson Med 49:722–730, 2003. © 2003 Wiley‐Liss, Inc.
Assessment of global and regional myocardial function in the mouse using cine and tagged MRI
Authors: Zhou Rong , Pickup Stephen , Glickson Jerry D. , Scott Craig H. , Ferrari Victor A.
Published: March 2003

Mouse models are expected to play an important role in future investigations of human cardiac diseases. In the present report, MRI methods for determining global and regional cardiac function in the mouse are demonstrated. ECG‐gated cine images were acquired in five C57BL/6 mice at physiological temperatures (37°C) and heart rates of 500 ± 50 beats per minute. Left ventricular mass, ejection fraction, and cardiac output were estimated from the resulting images. Regional myocardial function was also determined in three animals by application of 2D SPAtial Modulation of Magnetization (SPAMM) in combination with the cine protocol. The quality of the tagged images was sufficient to allow mapping of myocardial strains and displacements. The results of the regional strain analysis were consistent with similar studies in larger animals. This work demonstrates the first characterization of regional myocardial function in the mouse via SPAMM techniques. Magn Reson Med 49:760–764, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of new sequences for high‐resolution cartilage imaging
Authors: Hargreaves Brian A. , Gold Garry E. , Beaulieu Christopher F. , Vasanawala Shreyas S. , Nishimura Dwight G. , Pauly John M.
Published: March 2003

The high prevalence of osteoarthritis continues to demand improved accuracy in detecting cartilage injury and monitoring its response to different treatments. MRI is the most accurate noninvasive method of diagnosing cartilage lesions. However, MR imaging of cartilage is limited by scan time, signal‐to‐noise ratio (SNR), and image contrast. Recently, there has been renewed interest in SNR‐efficient imaging sequences for imaging cartilage, including various forms of steady‐state free‐precession as well as driven‐equilibrium imaging. This work compares several of these sequences with existing methods, both theoretically and in normal volunteers. Results show that the new steady‐state methods increase SNR‐efficiency by as much as 30% and improve cartilage‐synovial fluid contrast by a factor of three. Additionally, these methods markedly decrease minimum scan times, while providing 3D coverage without the characteristic blurring seen in fast spin‐echo images. Magn Reson Med 49:700–709, 2003. © 2003 Wiley‐Liss, Inc.
High‐resolution in vivo CBV mapping with MRI in wild‐type mice
Authors: Wu Ed X. , Wong Kelvin K. , Andrassy Martin , Tang Haiying
Published: March 2003

NMR microimaging has the potential to elucidate cerebrovascular abnormalities in mouse models. In this study, the relative regional cerebral blood volume (CBV) map is presented for C57BL6/J wild‐type mice. The CBV mapping was based on changes in the steady‐state NMR transverse relaxation rate (ΔR2) associated with the presence of a superparamagnetic intravascular contrast agent (MION) with a long blood halflife. The experiments were performed at 9.4 T at a voxel size of 100 μm × 100 μm × 600 μm. Fine details, such as the hippocampal and olfactory bulb area, were visualized in the CBV map. The relative regional CBV values of various brain regions were measured. The ΔR2 dosage dependency and MION tissue clearance in mouse are also reported. Magn Reson Med 49:765–770, 2003. © 2003 Wiley‐Liss, Inc.
Relaxation times of 31P‐metabolites in human calf muscle at 3 T
Authors: Meyerspeer Martin , Krššák Martin , Moser Ewald
Published: March 2003

Localized 31P‐STEAM experiments were performed at 3 T to estimate relaxation times of phosphorus‐containing metabolites in the human calf muscle in vivo. T1 and T2 times of PCr, Pi, and NTPs were measured in the resting calf muscle of healthy subjects by varying TR and TE. The localization performance of the 31P‐STEAM sequence was evaluated on a test object, resulting in a relative selection efficiency of 78 ± 1% and contamination from outside the voxel of 0 ± 2% under fully relaxed conditions. T1 relaxation times (±SD, n = 5) of Pi, PCr, γ‐NTP, α‐NTP, and β‐NTP obtained at 3 T are 5.2 ± 1.0 s, 6.4 ± 0.2 s, 4.5 ± 0.3 s, 2.6 ± 0.9 s, and 3.5 ± 1.1 s, respectively. T2 relaxation times (±SD, n = 6) of these metabolites are 148 ± 17 ms, 334 ± 30 ms, 78 ± 13 ms, 55 ± 7 ms, and 55 ± 10 ms, respectively. Spin‐lattice relaxation times established at 3 T are consistent with literature data at lower field strengths, whereas spin–spin relaxation times are lower. Several methodological considerations are discussed which may help improve quantification of metabolite concentrations in the human (calf) muscle in vivo by using localized noninvasive 31P‐MRS at 3 T, which is currently being tested for routine clinical applications. Magn Reson Med 49:620–625, 2003. © 2003 Wiley‐Liss, Inc.
In vivo measurement of brain metabolites using two‐dimensional double‐quantum MR spectroscopy—exploration of GABA levels in a ketogenic diet
Authors: Wang Zhiyue J. , Bergqvist Christina , Hunter Jill V. , Jin Dongzhu , Wang Dah‐Jyuu , Wehrli Suzanne , Zimmerman Robert A.
Published: March 2003

A localized proton 2D double‐quantum (DQ) spin‐echo spectroscopy technique was implemented on 1.5 T clinical MRI scanners for the detection of γ‐aminobutyrate (GABA) in the brain. The 2D approach facilitates separation of peaks overlapping with GABA in 1D DQ‐filtered (DQF) spectra. This technique was applied to four normal adult volunteers and four children with intractable epilepsy. The coefficient of variation of the level of GABA and overlapping macromolecules at F2 = 3.0 ppm and F1 = 4.8 ppm was 0.08 in normal subjects. Three patients received 2D MRS scans before and after initiation of the ketogenic diet (KD): one patient showed a trend of decreasing GABA throughout the study, and two patients showed low initial GABA levels that increased over time. In addition to major metabolites and GABA, low‐level metabolites (valine, leucine, and glutathione) were also identified in the 2D spectra. Magn Reson Med 49:615–619, 2003. © 2003 Wiley‐Liss, Inc.
Phased‐array MRI of canine prostate using endorectal and endourethral coils
Authors: Yung Andrew C. , Oner Ali Y. , Serfaty Jean‐Michel , Feneley Mark , Yang Xiaoming , Atalar Ergin
Published: March 2003

A four‐channel phased array consisting of one surface coil, two endorectal coils, and one flexible endourethral loop coil was designed for MRI of the canine prostate. The endorectal coils provide high signal in the posterior region of the prostate, while the endourethral and surface coils are sensitive to the central and anterior regions of the prostate. Gel phantom experiments indicate that the proposed phased‐array configuration generates 15 times more signal‐to‐noise ratio (SNR) than a combination of two surface coils and one endorectal coil within the posterior region of the prostate; the performance of the two configurations is comparable near the anterior prostate surface. Ultimate intrinsic SNR (UISNR) analysis was used to compare the proposed phased array's performance to the best possible SNR for external coils. This analysis showed that the proposed phased array outperforms the best‐case external coil within the posterior and central regions of the prostate by up to 20 times. In canine experiments in vivo, high‐resolution fast spin‐echo (FSE) images of the prostate were obtained with a pixel size of 230 μm obtained in 3 min 12 s. The proposed phased‐array design potentially can be used to increase the accuracy of prostate cancer staging and the feasibility of MR‐guided prostate interventions. Magn Reson Med 49:710–715, 2003. © 2003 Wiley‐Liss, Inc.
Spin‐echo fMRI in humans using high spatial resolutions and high magnetic fields
Authors: Yacoub Essa , Duong Timothy Q. , Van De Moortele Pierre‐Francois , Lindquist Martin , Adriany Gregor , Kim Seong‐Gi , Uğurbil Kâmil , Hu Xiaoping
Published: March 2003

The Hahn spin‐echo (HSE)‐based BOLD effect at high magnetic fields is expected to provide functional images that originate exclusively from the microvasculature. The blood contribution that dominates HSE BOLD contrast at low magnetic fields (e.g., 1.5 T), and degrades specificity, is highly attenuated at high fields because the apparent T2 of venous blood in an HSE experiment decreases quadratically with increasing magnetic field. In contrast, the HSE BOLD contrast is believed to arise from the microvasculature and increase supralinearly with the magnetic field strength. In this work we report the results of detailed and quantitative evaluations of HSE BOLD signal changes for functional imaging in the human visual cortex at 4 and 7 T. This study used high spatial resolution, afforded by the increased signal‐to‐noise ratio (SNR) of higher field strengths and surface coils, to avoid partial volume effects (PVEs), and demonstrated increased contrast‐to‐noise ratio (CNR) and spatial specificity at the higher field strengths. The HSE BOLD signal changes induced by visual stimulation were predominantly linearly dependent on the echo time (TE). They increased in magnitude almost quadratically in going from 4 to 7 T when the blood contribution was suppressed using Stejskal‐Tanner gradients that suppress signals from the blood due to its inhomogeneous flow and higher diffusion constant relative to tissue. The HSE signal changes at 7 T were modeled accurately using a vascular volume of 1.5%, in agreement with the capillary volume of gray matter. Furthermore, high‐resolution acquisitions indicate that CNR increased with voxel sizes < 1 mm3 due to diminishing white matter or cerebrospinal fluid‐space vs. gray matter PVEs. It was concluded that the high‐field HSE functional MRI (fMRI) signals originated largely from the capillaries, and that the magnitude of the signal changes associated with brain function reached sufficiently high levels at 7 T to make it a useful approach for mapping on the millimeter to submillimeter spatial scale. Magn Reson Med 49:655–664, 2003. © 2003 Wiley‐Liss, Inc.
Unsupervised reconstruction of a three‐dimensional left ventricular strain from parallel tagged cardiac images
Authors: Denney Thomas S. , Gerber Bernhard L. , Yan Litao
Published: March 2003

A new algorithm, called the Unsupervised Tag ExTraction and Heart strain(E) Reconstruction (UNTETHER) algorithm, is presented for quantifying three‐dimensional (3D) myocardial strain in tagged cardiac MR images. Five human volunteers and five postinfarct patients were imaged. 3D strains measured by UNTETHER and a user‐supervised technique were compared. Each study was analyzed in 49 ± 8 min with UNTETHER, compared to ∼4 hr with the user‐supervised technique. For pooled human data, the correlation coefficient between the two methods for circumferential shortening (Ecc) was r = 0.91 at the mid‐wall (P < 0.0005). UNTETHER is capable of measuring wall motion abnormalities resulting from coronary artery disease, and has the potential to overcome the main limitations (time and user‐supervision requirements) to routine clinical use of tagged cardiac MRI. Magn Reson Med 49:743–754, 2003. © 2003 Wiley‐Liss, Inc.
Local reconstruction of stenosed sections of artery using multiple MRA acquisitions
Authors: Herment A. , Roullot E. , Bloch I. , Jolivet O. , De Cesare A. , Frouin F. , Bittoun J. , Mousseaux E.
Published: March 2003

A method for reconstructing magnetic resonance angiography (MRA) volumes from successive acquisitions is described. The method is based on double oblique acquisitions of highly anisotropic MRA volumes, each of which corresponds to reduced k‐space filling. These partial k‐spaces are then combined to obtain a 3D k‐space adapted to the frequency spread of the angiographic image of the stenosis. The SNR‐resolution compromise of MRA is thus improved by focusing the acquisition on the most relevant k‐space regions. The reconstruction is performed directly in k‐space by averaging the partial k‐spaces. The feasibility of the method was demonstrated in studies on a Lucite stenosis phantom, on MRAs of carotid arteries using three bolus injections, and on MRAs of renal arteries using a single contrast injection. Magn Reson Med 49:731–742, 2003. © 2003 Wiley‐Liss, Inc.
Screening for risk of rehospitalization from home care: Use of the outcomes assessment information set and the probability of readmission instrument
Authors: Bowles Kathryn H. , Cater Jacqueline R.
Published: March 2003

The purpose of this study was to evaluate the Outcomes Assessment Information Set (OASIS) compared with the Probability of Readmission (Pra) instrument for use in predicting rehospitalization during home care. Using logistic regression and receiver operating characteristic (ROC) curve analysis, the Pra instrument was found to be significantly better at predicting rehospitalization than the OASIS case mix weight, clinical, or service scores. The area under the curve (AUC) for the Pra was .686 compared with .549 for the OASIS case mix weight (p = .010). Similar results were found for the OASIS clinical and service scores. The AUC for the function score of ≥2 (.599) provided the closest approximation to the Pra (.686), and the difference between the two was not statistically significant (p = .120). The OASIS function score could be used to identify at‐risk home care patients without having to also use the Pra instrument. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:118–127, 2003
Toward a metasynthesis of qualitative findings on motherhood in HIV‐positive women
Authors: Sandelowski Margarete , Barroso Julie
Published: March 2003

A qualitative metasynthesis of qualitative findings ought to be more than a mere summary of those findings. Yet the processes by which the interpretive innovation expected of qualitative metasynthesis projects can be achieved remain opaque. Several analytic devices for the metasynthesis of findings were clarified in the course of an ongoing methodological project involving 45 reports of qualitative studies of HIV‐positive women. These devices include the creation of a taxonomy of findings, the explicit use of sustained comparisons, the translation of in vivo concepts, and the use of imported concepts. Any qualitative metasynthesis of findings constitutes an interpretation at least three times removed from the lives represented in them. Clarifying the analytic devices used to create such metasyntheses is essential to demonstrating that despite being far away from participants' lives, these interpretations remain close to them. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:153–170, 2003
Psychometric characteristics of the breastfeeding self‐efficacy scale: Data from an Australian sample
Authors: Creedy Debra K. , Dennis Cindy‐Lee , Blyth Rosemary , Moyle Wendy , Pratt Jan , De Vries Susan M.
Published: March 2003

Many new mothers discontinue breastfeeding prematurely because of difficulties encountered rather than maternal choice. Research has shown that a significant predictor of breastfeeding duration is a mother's confidence in her ability to breastfeed. To measure breastfeeding confidence, the Breastfeeding Self‐Efficacy Scale (BSES) was developed and psychometrically tested at 1 week postpartum. The purpose of this methodological study was to psychometrically test the BSES antenatally and at 1 week and 4 months postpartum in a sample of Australian women and to determine predictive validity. The psychometric assessment of the original BSES study was replicated, including internal consistency, principal components factor analysis, comparison of contrasted groups, and correlations with a similar construct. Support for predictive validity was demonstrated through positive correlations and significant mean differences between antenatal BSES scores and infant‐feeding method at 1 week and 4 months postpartum. The BSES is now considered ready for both research and clinical use (a) to identify new mothers with low breastfeeding confidence who require additional assistance, (b) to assess breastfeeding behaviors and cognitions in order to have individualized confidence‐building strategies, and (c) to assist in the evaluation of various nursing interventions. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:143–152, 2003
Effects of stress management on PNI‐based outcomes in persons with HIV disease
Authors: McCain Nancy L. , Munjas Barbara A. , Munro Cindy L. , Elswick R. K. , Robins Jo L. Wheeler , Ferreira‐Gonzalez Andrea , Baliko Beverly , Kaplowitz Lisa G. , Fisher Evelyn J. , Garrett Carleton T. , Brigle Kevin E. , Kendall Linda C. , Lucas Valentina , Cochran Katherine L.
Published: March 2003

A pretest–posttest, repeated‐measures design was used to evaluate the effects of two stress management interventions on a battery of outcomes derived from a psychoneuroimmunological (PNI) framework. The effects of cognitive‐behavioral relaxation training groups (CBSM) and social support groups (SSG) were compared with a WAIT‐listed control group on the outcomes of psychosocial functioning, quality of life, neuroendocrine mediation, and somatic health. Participants were 148 individuals (119 men, 29 women), diagnosed with HIV disease; 112 (76%) completing the study groups. Using analysis of covariance, the CBSM group was found to have significantly higher postintervention emotional well‐being and total quality‐of‐life scores than did either the SSG or WAIT groups. SSG participants had significantly lower social/family well‐being scores immediately postintervention and lower social support scores after 6 months. The findings point to a pressing need for further, well‐controlled research with these common intervention modalities. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:102–117, 2003
Teaching nursing research to undergraduates: A text analysis of instructors' intentions
Authors: Porter Eileen J. , Mansour Tamam B.
Published: March 2003

Reviews of teaching strategies for undergraduate nursing research have been organized according to (a) the type of learning to be achieved, such as learning by doing, or (b) the specific teaching strategy, such as a poster session. For this text analysis, a new tack was taken to reveal the intentions of undergraduate nursing research instructors for student learning. Giorgi's (1985) descriptive phenomenological method was used to analyze 77 narrative reports of instructors about research teaching strategies. Seven intentions were identified, including desensitizing negative perceptions about research and stimulating collaborative learning about research. The intentions were contrasted in scope and relevance to frameworks organized according to learning goals or teaching techniques. The relevance of the intentions was considered in relation to critical trends influencing nursing education. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:128–142, 2003
Situated clinical reasoning: Distinguishing acute confusion from dementia in hospitalized older adults
Authors: McCarthy Marianne
Published: March 2003

In this study a dimensional analysis approach was used to explore the clinical reasoning of nurses who care for hospitalized older adults to identify factors that might explain their failure to detect acute confusion and to distinguish it from dementia in this patient population. Data analysis yielded a grounded theory of situated clinical reasoning, which proposes that the ability of nurses to identify acute confusion varies widely. This variation can be attributed to the differences in nurses' philosophical perspectives on aging. According to this theory, three distinct perspectives are unwittingly embraced by nurses who care for older patients. These perspectives influence how nurses characterize aging and the aged and condition the ways in which they judge and ultimately deal with older adults in clinical situations. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:90–101, 2003
Applying TAF to generate efficient derivative code of Fortran 77‐95 programs
Authors: Giering Ralf , Kaminski Thomas
Published: April 2003

This paper features FastOpt's automatic differentiation (AD) tool Transformation of Algorithms in Fortran (TAF), a source to source translator for programs written in Fortran 77‐95. TAF and its predecessor TAMC have a long record of successful large‐scale applications. Here we give an overview on how TAF approaches typical challenges of AD such as handling of badly written program code, of large memory/disk requirements, of iterative solvers or of black box routines. We also point out, where the user is required to prepare his program code prior to invoking TAF.
Preparation, characterization, and properties of novolac‐type phenolic/SiO2 hybrid organic–inorganic nanocomposite materials by sol–gel method
Authors: Chiang Chin‐Lung , Ma Chen‐Chi M. , Wu Dai‐Lin , Kuan Hsu‐Chiang
Published: March 2003

This article describes the preparation of novolac‐type phenolic resin/silica hybrid organic–inorganic nanocomposite, with a sol–gel process. The coupling agent was used to improve the interface between the organic and inorganic phases. The effect of the structure of the nanocomposite on its physical and chemical properties is discussed. The coupling agent reacts with the resin to form covalent bonds. The structure of the modified hybrid nanocomposites was identified with a Fourier transform infrared spectroscope. The silica network was characterized by nuclear magnetic resonance imaging (29Si NMR). Results revealed that Q4 (tetrasubstituted) and T3 (trisubstituted) are the dominant microstructures. The size of the silica in the phenolic resin was characterized with a scanning electron microscope. The size of the particles of inorganic silica in the modified system was less than 100 nm. The nanocomposite exhibited good transparency. Moreover, the thermal and mechanical properties exhibited significant improvement. The modified hybrid composite exhibited favorable thermal properties. The temperature at which a weight loss of 5% occurred increased from 281 to 350 °C. The flexural strength increased by 6–30%. The limiting oxygen index of the nanocomposite reached 37, and the Underwriters Laboratory test was 94V‐0. Consequently, these materials possess excellent flame‐retardant properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 905–913, 2003
Ethyl‐iso‐butylaluminoxane activated metallocene catalyst for olefin polymerization
Authors: Wang Qi , Hong Jian , Fan Zhiqiang , Tao Ruoyuan
Published: March 2003

Ethylene and propylene were polymerized by different combinations of metallocenes and aluminoxanes. Ethyl‐iso‐butylaluminoxane (EBAO), which could be easily obtained by direct hydrolysis of Et3Al/iso‐Bu3Al in toluene with water, displayed as good polymerization activity as methylaluminoxane when it was paired with some metallocenes. The UV–visible spectroscopic study on different metallocene/aluminoxane pairs suggests that tightness of the ionic pairs generated from the reaction between metallocene and aluminoxane is different for a fixed metallocenium. The loose ionic pair derived from EBAO prefers the monomer propagation and hinders the interaction between active species, which results in high catalytic activity and molecular weight. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 998–1003, 2003
Copolymerization of styrene and conjugated dienes with half‐sandwich titanium(IV) catalysts: The effect of the ligand structure on the monomer reactivity, monomer sequence distribution, and insertion mode of dienes
Authors: Naga Naofumi , Imanishi Yukio
Published: March 2003

The copolymerization of styrene and 1,3‐butadiene (Bd) or isoprene (Ip) was carried out with half‐sandwich titanium(IV) Cp′TiCl3 catalysts (where Cp′ is cyclopentadienyl 1, indenyl 2, or pentamethylcyclopentadienyl 3) with methylaluminoxane as a cocatalyst. For the copolymerization with Bd, catalyst 3 gave the copolymers containing the highest amount of Bd among the catalysts used. The resulting copolymers were composed of a styrene–Bd multiblock sequence. High melting points were observed in the copolymers prepared with catalyst 1. The structures of hydrogenated poly(styrene‐co‐Bd) were studied by 13C NMR spectroscopy, and the long styrene sequence length was detected in the copolymers prepared with catalyst 1. For styrene/Ip copolymerization, random copolymers were obtained. Among the used catalysts, catalyst 1 gave the copolymers containing the highest amount of Ip. The copolymers prepared with catalyst 1 showed a steep melting point depression with increasing Ip content because of the high ratio of 1,4‐inserted Ip units and/or the low molecular weights of the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 939–946, 2003
Helicity induction on a poly(phenylacetylene) derivative bearing aza‐18‐crown‐6 ether pendants in water
Authors: Nonokawa Ryuji , Yashima Eiji
Published: March 2003

A stereoregular poly(phenylacetylene) bearing the bulky aza‐18‐crown‐6 ether as the pendant (poly‐1) formed a predominantly one‐handed helical conformation upon complexation with various chiral compounds, such as amino acids, peptides, aminosugars, amines, and amino alcohols in water. The complexes exhibited an induced circular dichroism (ICD) in the UV–visible region of the polymer main chain. Therefore, poly‐1 can be used as a novel probe for determining the chirality of chiral compounds in water. The assay of 19 common free L‐amino acids gave the same ICD sign at 0 °C except for L‐phenylalanine. The effects of pH, temperature, guest concentration, and organic solvent content on the ICD during the complexation of poly‐1 with chiral compounds were also investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1004–1013, 2003
Isolation and identification of cyclic oligomers of the poly(ethylene terephthalate)–poly(ethylene isophthalate) copolymer
Authors: Lim Byung‐Ho , Kwon Soo‐Han , Kang En‐Chang , Park Heon , Lee Hyun‐Woo , Kim Whan‐Gi
Published: March 2003

New cyclic oligomers of the copolymer of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) were isolated and identified. A condensation polymerization was carried out at a high temperature, and the solid‐state polymerization that followed yielded the high molecular weight polymer. The oligomers were extracted from the high molecular weight PET–PEI copolymer and separated with preparative high performance liquid chromatography techniques. Their chemical structures and properties were analyzed and determined by 1H NMR, differential scanning calorimetry, and mass spectroscopy. The oligomers observed at early retention times were a cyclic dimer and cyclic trimers and consisted of [GT]3, [GI]2, [GI]3, [GT]2[GI]1, and [GT]1[GI]2. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 881–889, 2003
Molecular and structural analysis of a triepoxide‐modified poly(ethylene terephthalate) from rheological data
Authors: Dhavalikar R. , Yamaguchi M. , Xanthos M.
Published: March 2003

The effects of reactive melt modification of poly(ethylene terephthalate) (PET) with a multifunctional epoxide—triglycidyl isocyanurate—that lead to chain extension/branching and formation of gel‐like structures were rheologically characterized. The storage and loss moduli and the complex viscosity of the modified PET were larger than those of the unmodified PET. The elastic or solidlike behavior of PET was enhanced after reactive modification as a result of chain extension/branching. Modified Cole–Cole plots revealed that the modified resins show higher elasticity than the unmodified one. Reactive modification characterized by the presence of long‐chain branching resulted in a wider molecular weight distribution. The effects of mixing temperature and the concentration of modifier corresponding to different stoichiometries were investigated. Higher amounts of modifier resulted in a polymeric structure near the sol–gel transition point whose linear viscoelastic properties obey scaling law. The relaxation spectrum was calculated from the oscillatory shear data by Tschoegl equations. Certain modified resins have rheological properties suitable for process operations such as extrusion foaming, blow molding, and thermoforming. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 958–969, 2003
Convenient synthesis and polymerization of 5,6‐disubstituted dithiophthalides toward soluble poly(isothianaphthene): An initial spectroscopic characterization of the resulting low‐band‐gap polymers
Authors: Polec I. , Henckens A. , Goris L. , Nicolas M. , Loi M. A. , Adriaensens P. J. , Lutsen L. , Manca J. V. , Vanderzande D. , Sariciftci N. S.
Published: March 2003

A new synthetic procedure toward substituted dithiophthalides, 5,6‐dialkyloxydithiophthalide and 5,6‐dithioalkyldithiophthalide, is presented. 5,6‐Dithiooctyldithiophthalide was obtained from 4,5‐dichlorophthalic acid in an eight‐step reaction with an overall yield of 26%. 5,6‐Dioctyloxydithiophthalide was obtained from 4,5‐dihydroxyphthalic acid dimethyl ester in a seven‐step reaction (overall yield = 15%). Both monomers were polymerized by a thermal and nonoxidative polymerization that resulted in soluble poly(isothianaphthene) derivatives with a band gap of about 1.2 eV. Photoinduced absorption measurements revealed the existence of charged excitations upon illumination. The photoinduced charge generation, combined with the extensive light‐harvesting properties and the easy processability, makes these materials quite promising for photovoltaic applications. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1034–1045, 2003
Synthesis and ring‐opening (co)polymerization of L‐lysine N‐carboxyanhydrides containing labile side‐chain protective groups
Authors: Hernández Juan Rodríguez , Klok Harm‐Anton
Published: March 2003

This contribution describes the synthesis and ring‐opening (co)polymerization of several L‐lysine N‐carboxyanhydrides (NCAs) that contain labile protective groups at the ϵ‐NH2 position. Four of the following L‐lysine NCAs were investigated: Nϵ‐trifluoroacetyl‐L‐lysine N‐carboxyanhydride, Nϵ‐(tert‐butoxycarbonyl)‐L‐lysine N‐carboxyanhydride, Nϵ‐(9‐fluorenylmethoxycarbonyl)‐L‐lysine N‐carboxyanhydride, and Nϵ‐(6‐nitroveratryloxycarbonyl)‐L‐lysine N‐carboxyanhydride. In contrast to the harsh conditions that are required for acidolysis of benzyl carbamate moieties, which are usually used to protect the ϵ‐NH2 position of L‐lysine during NCA polymerization, the protective groups of the L‐lysine NCAs presented here can be removed under mildly acidic or basic conditions or by photolysis. As a consequence, these monomers may allow access to novel peptide hybrid materials that cannot be prepared from ϵ‐benzyloxycarbonyl‐L‐lysine N‐carboxyanhydride (Z‐Lys NCA) because of side reactions that accompany the removal of the Z groups. By copolymerization of these L‐lysine NCAs with labile protective groups, either with each other or with γ‐benzyl‐L‐glutamate N‐carboxyanhydride or Z‐Lys NCA, orthogonally side‐chain‐protected copolypeptides with number‐average degrees of polymerization ≤20 were obtained. Such copolypeptides, which contain different side‐chain protective groups that can be removed independently, are interesting for the synthesis of complex polypeptide architectures or can be used as scaffolds for the preparation of synthetic antigens or protein mimetics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1167–1187, 2003
Polymer hybrids with functionalized silsesquioxanes via two physical interactions in one system
Authors: Kim Kyung‐Min , Chujo Yoshiki
Published: March 2003

Transparent and homogeneous polymer hybrids were obtained from a series of random styrene/N,N‐dimethylacrylamide copolymers (PSnPAm) and octa(3‐hydroxypropyldimethylsiloxy)octasilsesquioxane (Cube‐OH) by means of the sol–gel reaction of phenyltrimethoxysilane (PTMOS). The resulting ternary polymer hybrids were prepared via two simultaneous physical interactions [hydrogen‐bonding and aromatic (π–π) interactions] in one system. Cube‐OH and PTMOS were used to form hydrogen‐bonding and aromatic (π–π) interactions, respectively, with the organic copolymer. When PS90PA10 was used as an organic polymer for the two physical interactions, the transparency was maintained when the weight ratio of Cube‐OH to PTMOS was increased to 0.5. However, the polymer hybrids with PS65PA35 produced optically translucent or turbid materials, which indicated the phase separation of the organic polymer and silica gel. The homogeneity of the ternary polymer hybrids was dependent on the balance between the intensity of the hydrogen‐bonding interaction and that of the aromatic (π–π) interaction. The homogeneity was supported by the results of Fourier transform infrared, differential scanning calorimetry, scanning electron microscopy, and X‐ray diffraction, which demonstrated a nanometer‐level integration of the organic polymer, Cube‐OH, and silica gel. The initial decomposition temperature of the ternary polymer hybrids was more dependent on the amount of PTMOS than on that of Cube‐OH. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1306–1315, 2003