bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractMulticomponent 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

AbstractSkeletal 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

AbstractEthanol (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

AbstractThe 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

AbstractQuantitative 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

AbstractGlutathione 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

AbstractAnionic 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

AbstractA 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

AbstractSinusoidal 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

AbstractThe 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

AbstractA 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

AbstractMouse 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

AbstractThe 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

AbstractNMR 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

AbstractLocalized 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

AbstractA 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

AbstractA 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.