bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resting‐state functional connectivity of the rat brain
Authors: Pawela Christopher P. , Biswal Bharat B. , Cho Younghoon R. , Kao Dennis S. , Li Rupeng , Jones Seth R. , Schulte Marie L. , Matloub Hani S. , Hudetz Anthony G. , Hyde James S. 
Published: April 2008

AbstractRegional‐specific average time courses of spontaneous fluctuations in blood oxygen level dependent (BOLD) MRI contrast at 9.4T in lightly anesthetized resting rat brain are formed, and correlation coefficients between time course pairs are interpreted as measures of connectivity. A hierarchy of regional pairwise correlation coefficients (RPCCs) is observed, with the highest values found in the thalamus and cortex, both intra‐ and interhemisphere, and lower values between the cortex and thalamus. Independent sensory networks are distinguished by two methods: data driven, where task activation defines regions of interest (ROI), and hypothesis driven, where regions are defined by the rat histological atlas. Success in these studies is attributed in part to the use of medetomidine hydrochloride (Domitor) for anesthesia. Consistent results in two different rat‐brain systems, the sensorimotor and visual, strongly support the hypothesis that resting‐state BOLD fluctuations are conserved across mammalian species and can be used to map brain systems. Magn Reson Med 59:1021–1029, 2008. © 2008 Wiley‐Liss, Inc.
Interleaved narrow‐band PRESS sequence with adiabatic spatial‐spectral refocusing pulses for 1H MRSI at 7T
Authors: Balchandani Priti , Pauly John , Spielman Daniel 
Published: April 2008

AbstractProton magnetic resonance spectroscopic imaging (1H MRSI) is a useful technique for measuring metabolite levels in vivo, with Choline (Cho), Creatine (Cre), and N‐Acetyl‐Aspartate (NAA) being the most prominent MRS‐detectable brain biochemicals. 1H MRSI at very high fields, such as 7T, offers the advantages of higher SNR and improved spectral resolution. However, major technical challenges associated with high‐field systems, such as increased B1 and B0 inhomogeneity as well as chemical shift localization (CSL) error, degrade the performance of conventional 1H MRSI sequences. To address these problems, we have developed a Position Resolved Spectroscopy (PRESS) sequence with adiabatic spatial‐spectral (SPSP) refocusing pulses, to acquire multiple narrow spectral bands in an interleaved fashion. The adiabatic SPSP pulses provide magnetization profiles that are largely invariant over the 40% B1 variation measured across the brain at 7T. Additionally, there is negligible CSL error since the transmit frequency is separately adjusted for each spectral band. in vivo 1H MRSI data were obtained from the brain of a normal volunteer using a standard PRESS sequence and the interleaved narrow‐band PRESS sequence with adiabatic refocusing pulses. In comparison with conventional PRESS, this new approach generated high‐quality spectra from an appreciably larger region of interest and achieved higher overall SNR. Magn Reson Med 59:973–979, 2008. © 2008 Wiley‐Liss, Inc.
Accelerated proton echo planar spectroscopic imaging (PEPSI) using GRAPPA with a 32‐channel phased‐array coil
Authors: Tsai Shang‐Yueh , Otazo Ricardo , Posse Stefan , Lin Yi‐Ru , Chung Hsiao‐Wen , Wald Lawrence L. , Wiggins Graham C. , Lin Fa‐Hsuan 
Published: April 2008

AbstractParallel imaging has been demonstrated to reduce the encoding time of MR spectroscopic imaging (MRSI). Here we investigate up to 5‐fold acceleration of 2D proton echo planar spectroscopic imaging (PEPSI) at 3T using generalized autocalibrating partial parallel acquisition (GRAPPA) with a 32‐channel coil array, 1.5 cm3 voxel size, TR/TE of 15/2000 ms, and 2.1 Hz spectral resolution. Compared to an 8‐channel array, the smaller RF coil elements in this 32‐channel array provided a 3.1‐fold and 2.8‐fold increase in signal‐to‐noise ratio (SNR) in the peripheral region and the central region, respectively, and more spatial modulated information. Comparison of sensitivity‐encoding (SENSE) and GRAPPA reconstruction using an 8‐channel array showed that both methods yielded similar quantitative metabolite measures (P > 0.1). Concentration values of N‐acetyl‐aspartate (NAA), total creatine (tCr), choline (Cho), myo‐inositol (mI), and the sum of glutamate and glutamine (Glx) for both methods were consistent with previous studies. Using the 32‐channel array coil the mean Cramer–Rao lower bounds (CRLB) were less than 8% for NAA, tCr, and Cho and less than 15% for mI and Glx at 2‐fold acceleration. At 4‐fold acceleration the mean CRLB for NAA, tCr, and Cho was less than 11%. In conclusion, the use of a 32‐channel coil array and GRAPPA reconstruction can significantly reduce the measurement time for mapping brain metabolites. Magn Reson Med 59:989–998, 2008. © 2008 Wiley‐Liss, Inc.
Off‐resonance‐dependent slice profile effects in balanced steady‐state free precession imaging
Authors: Staehle F. , Leupold J. , Hennig J. , Markl M. 
Published: April 2008

AbstractThe purpose of this study was the simulation and measurement of balanced steady‐state free precession (bSSFP) slice profiles for a detailed analysis of the influence of off‐resonance effects on slice profile shape and bSSFP signal intensity. Due to the frequency response function of the bSSFP sequence, measurements that are not on‐resonance result in broadened effective slice profiles with different off‐resonance‐dependent shapes and signal intensities. In this study, bSSFP slice profile effects and their dependence on off‐resonance were investigated based on bSSFP signal simulations of phantom data as well as blood and tissue. For a better assessment of the similarity of measured and simulated slice profiles the field map was integrated in the slice profile simulations. The results demonstrate that simulations can accurately predict bSSFP slice profiles. Both measurements and simulations indicate that there is a substantial increase in signal intensity close to the banding artifacts, i.e., at spatial locations with off‐resonance frequencies corresponding to a dephasing/TR = ± π resulting in signal void (bands). For routine bSSFP imaging, off‐resonance‐dependent slice broadening may thus result in a substantial difference between nominal and true slice thickness and lead to spatially varying slice thickness and signal intensities across the imaging slice. Magn Reson Med 59:1197–1202, 2008. © 2008 Wiley‐Liss, Inc.
Wireless self‐gated multiple‐mouse cardiac cine MRI
Authors: Esparza‐Coss Emilio , Ramirez Marc S. , Bankson James A. 
Published: April 2008

AbstractDespite the excellent image‐contrast capability of MRI and the ability to synchronize MRI with the murine cardiac cycle, this technique is underused for assessing mouse models of cardiovascular disease because of its perceived cost and complexity. This perception stems, in part, from complications associated with the placement and adjustment of electrocardiographic leads that may interact with gradient pulses and the relatively long acquisition times required with traditional gating schemes. To improve the efficiency and reduce the cost and complexity of using cardiac MRI in mice, we combined wireless self‐gating techniques (with which we derived cardiac synchronization signals from acquired data) with an imaging technique that acquires multislice cardiac cine images from four mice simultaneously. As a result, the wireless self‐gated acquisitions minimized animal preparation time and improved image quality. The simultaneous acquisition of cardiac cine data from multiple animals greatly increased throughput and reduced costs associated with instrument access. Magn Reson Med 59:1203–1206, 2008. © 2008 Wiley‐Liss, Inc.
Evaluation of temporal and spatial characteristics of 2D HYPR processing using simulations
Authors: Wu Yan , Wieben Oliver , Mistretta Charles A. , Korosec Frank R. 
Published: April 2008

AbstractHighly constrained back‐projection (HYPR) is a data acquisition and reconstruction method that provides very rapid frame update rates and very high spatial resolution for a time series of images while maintaining a good signal‐to‐noise ratio and high image quality. In this study we used simulations to evaluate the temporal and spatial characteristics of images produced using the HYPR algorithm. The simulations demonstrate that spatial accuracy is well maintained in the images and the temporal changes in signal intensity are represented with high fidelity. The waveforms representing signal intensity as a function of time obtained from regions‐of‐interest placed in simulated objects track the true curves very well, with variations from the truth occurring only when objects with very different temporal behavior are very close to each other. However, even when objects with different temporal characteristics are touching, their influences on each other are small. Magn Reson Med 59:1090–1098, 2008. © 2008 Wiley‐Liss, Inc.
Regional metabolite T2 in the healthy rhesus macaque brain at 7T
Authors: Liu Songtao , Gonen Oded , Fleysher Lazar , Fleysher Roman , Soher Brian J. , Pilkenton Sarah , Lentz Margaret R. , Ratai Eva‐Maria , González R. Gilberto 
Published: April 2008

AbstractAlthough the rhesus macaque brain is an excellent model system for the study of neurological diseases and their responses to treatment, its small size requires much higher spatial resolution, motivating use of ultra‐high‐field (B0) imagers. Their weaker radio‐frequency fields, however, dictate longer pulses; hence longer TE localization sequences. Due to the shorter transverse relaxation time (T2) at higher B0s, these longer TEs subject metabolites to T2‐weighting, that decrease their quantification accuracy. To address this we measured the T2s of N‐acetylaspartate (NAA), choline (Cho), and creatine (Cr) in several gray matter (GM) and white matter (WM) regions of four healthy rhesus macaques at 7T using three‐dimensional (3D) proton MR spectroscopic imaging at (0.4 cm)3 = 64 μl spatial resolution. The results show that macaque T2s are in good agreement with those reported in humans at 7T: 169 ± 2.3 ms for NAA (mean ± SEM), 114 ± 1.9 ms for Cr, and 128 ± 2.4 ms for Cho, with no significant differences between GM and WM. The T2 histograms from 320 voxels in each animal for NAA, Cr, and Cho were similar in position and shape, indicating that they are potentially characteristic of “healthy” in this species. Magn Reson Med 59:1165–1169, 2008. © 2008 Wiley‐Liss, Inc.
System identification theory in pharmacokinetic modeling of dynamic contrast‐enhanced MRI: Influence of contrast injection
Authors: Aerts H.J.W.L. , van Riel N.A.W. , Backes W.H. 
Published: April 2008

AbstractOptimization of experimental settings of dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI), like the contrast administration protocol, is of great importance for reliable quantification of the microcirculatory properties, such as the volume transfer‐constant Ktrans. Using system identification theory and computer simulations, the confounding effects of volume, rate and multiplicity of a contrast injection on the reliability of Ktrans estimation was assessed. A new tracer‐distribution model (TDM), based on in vivo data from rectal cancer patients, served to describe the relationship between the contrast agent injection and the blood time‐course. A pharmacokinetic model (PKM) was used to describe the relation between the blood and tumor tissue time‐courses. By means of TDM and PKM in series, the tissue‐transfer function of the PKM was analyzed. As both the TDM and PKM represented low‐frequency‐pass filters, the energy‐density at low frequencies of the blood and tissue time‐courses was larger than at high frequencies. The simulations, based on measurements in humans, predict that the Ktrans is most reliable with a high injection volume administered in a single injection, where high rates only modestly improve Ktrans. Magn Reson Med 59:1111–1119, 2008. © 2008 Wiley‐Liss, Inc.
Generalized k‐space decomposition with chemical shift correction for non‐cartesian water‐fat imaging
Authors: Brodsky Ethan K. , Holmes James H. , Yu Huanzhou , Reeder Scott B. 
Published: April 2008

AbstractChemical‐shift artifacts associated with non‐Cartesian imaging are more complex to model and less clinically acceptable than the bulk fat shift that occurs with conventional spin‐warp Cartesian imaging. A novel k‐space based iterative decomposition of water and fat with echo asymmetry and least‐squares estimation (IDEAL) approach is introduced that decomposes multiple species while simultaneously correcting distortion of off‐resonant species. The new signal model accounts for the additional phase accumulated by off‐resonant spins at each point in the k‐space acquisition trajectory. This phase can then be corrected by adjusting the decomposition matrix for each k‐space point during the final IDEAL processing step with little increase in reconstruction time. The technique is demonstrated with water‐fat decomposition using projection reconstruction (PR)/radial, spiral, and Cartesian spin‐warp imaging of phantoms and human subjects, in each case achieving substantial correction of chemical‐shift artifacts. Simulations of the point‐spread‐function (PSF) for off‐resonant spins are examined to show the nature of the chemical‐shift distortion for each acquisition. Also introduced is an approach to improve the signal model for species which have multiple resonant peaks. Many chemical species, including fat, have multiple resonant peaks, although such species are often approximated as a single peak. The improved multipeak decomposition is demonstrated with water‐fat imaging, showing a substantial improvement in water‐fat separation. Magn Reson Med 59:1151–1164, 2008. © 2008 Wiley‐Liss, Inc.
Simultaneous acquisition of MR angiography and venography (MRAV)
Authors: Du Yiping P. , Jin Zhaoyang 
Published: April 2008

AbstractA dual‐echo pulse sequence for simultaneous acquisition of MR angiography and venography (MRAV) is developed. Data acquisition of the second echo for susceptibility‐weighted imaging–based MR venography is added to the conventional three‐dimensional (3D) time‐of‐flight (TOF) MRA pulse sequence. Using this dual‐echo acquisition approach, the venography data can be acquired without increasing the repetition time, and, therefore, the scan duration of routine TOF MRA scans is maintained. The feasibility of simultaneous acquisition of MRAV is presented in brain scans at different spatial resolutions. The effect of spatial resolution on vein‐to‐background contrast is also demonstrated. Venous contrast is improved in high‐resolution (0.52 × 0.52 × 1.6 mm3) images compared to that in standard‐resolution (0.78 × 0.78 × 1.6 mm3) images. This MRAV technique enables the acquisition of MR venography without the need of an extra scan or injection of contrast agent in routine clinical brain exams at 3T. Magn Reson Med 59:954–958, 2008. © 2008 Wiley‐Liss, Inc.
Evidence for enhanced functional activity of cervical cord in relapsing multiple sclerosis
Authors: Agosta F. , Valsasina P. , Rocca M.A. , Caputo D. , Sala S. , Judica E. , Stroman P.W. , Filippi M. 
Published: April 2008

AbstractFunctional MRI (fMRI) was used to assess proprioceptive‐associated cervical cord activity in 24 relapsing multiple sclerosis (MS) patients and 10 controls. Cord and brain conventional and diffusion tensor (DT) MRI were also acquired. fMRI was performed using a block design during a proprioceptive stimulation consisting of a passive flexion‐extension of the right upper limb. Cord lesion number, cross‐sectional area, mean diffusivity (MD) and fractional anisotropy (FA), whole brain and left corticospinal tract lesion volume (LV), gray matter (GM) MD, and normal‐appearing white matter (NAWM) MD and FA were calculated. MS patients had higher average cord fMRI signal changes than controls (3.4% vs. 2.7%, P = 0.03). Compared to controls, MS patients also had a higher average signal change in the anterior section of the right cord at C5 (P = 0.005) and left cord at C5–C6 (P = 0.03), whereas no difference was found in the other cord sections. Cord average signal change correlated significantly with cord FA and brain left corticospinal tract LV, GM‐MD, and NAWM‐FA. This study shows an abnormal pattern of activations in the cervical cord of MS patients following proprioceptive stimulation. Cord fMRI changes might have a role in limiting the clinical consequences of MS associated with irreversible tissue damage. Magn Reson Med 59:1035–1042, 2008. © 2008 Wiley‐Liss, Inc.
Semiautomatic off‐resonance correction in spiral imaging
Authors: Chen Weitian , Meyer Craig H. 
Published: April 2008

AbstractSpiral scanning is a promising MRI method, but one limitation is that off‐resonance effects can cause image blurring. Most current off‐resonance correction methods for spiral imaging require an accurate field map, which is difficult to obtain in many applications. Automatic methods can perform off‐resonance correction without acquiring a field map. However, these methods are computationally inefficient and relatively prone to estimation error. This study describes a new semiautomatic off‐resonance correction method that combines an automatic method with a low resolution field map acquisition for off‐resonance correction in spiral scanning. Experiments demonstrate that this method is more robust than conventional automatic off‐resonance correction and can provide more accurate off‐resonance correction than conventional field map based methods. The proposed method is also computationally efficient and has been implemented for online reconstruction. Magn Reson Med 59:1212–1219, 2008. © 2008 Wiley‐Liss, Inc.
Optimization framework for calibration of constitutive models enhanced by neural networks
Authors: Obrzud Rafał F. , Vulliet Laurent , Truty Andrzej 
Published: April 2008

AbstractA two‐level procedure designed for the estimation of constitutive model parameters is presented in this paper. The neural network (NN) approach at the first level is applied to achieve the first approximation of parameters. This technique is used to avoid potential pitfalls related to the conventional gradient‐based optimization techniques, considered here as a corrector that improves predicted parameters. The feed‐forward NN (FFNN) and the modified Gauss–Newton algorithms are briefly presented. The proposed framework is verified for the elasto‐plastic modified Cam Clay model that can be calibrated based on standard triaxial laboratory tests, i.e. the isotropic consolidation test and the drained compression test. Two different formulations of the input data to the NN, enhanced by a dimensional reduction of experimental data using principal component analysis, are presented. The determination of model characteristics is demonstrated, first on numerical pseudo‐experiments and then on the experimental data. The efficiency of the proposed approach by means of accuracy and computational effort is also discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Retrospective analysis of 65 Chinese children with acute promyelocytic leukemia: A single center experience
Authors: Zhang Li , Zhao Hui , Zhu Xiaofan , Chen Yumei , Zou Yao , Chen Xiaojuan 
Published: April 2008

AbstractBackgroundThere are very limited data reported about childhood acute promyelocytic leukemia (APL), especially with arsenic trioxide (As2O3) treatment. We review the clinical course and treatment outcome of 65 children APL.ProcedureBetween January 1999 and December 2005, 65 children (<18 years) with newly diagnosed APL were treated.ResultsThree groups of patients were identified according to the different induction regimens. Forty patients were given ATRA alone (group 1, G1), 8 patients were given As2O3 alone (group 2, G2), 15 patients (group 3, G3) were treated with combination of ATRA and As2O3. Two patients received cytosine arabinoside and died at days 2 and 4, respectively. The CR rate of G1 was 95% (38/40). The overall CR rate of G2+G3 was 91.3% (21/23). Toxicity of ATRA and As2O3 were minimal and recoverable during induction. Five children had a hematologic relapse and two developed molecular relapse. Five of them were successfully treated with ATRA alone or combined with As2O3. The 5‐year estimate of EFS, DFS and OS between G1 and G2+G3 has no difference.ConclusionAs2O3 is an effective and well tolerable therapy for children with APL and it may be used in those who have dose limiting side effects of ATRA, but also for those with newly diagnosed or relapsed APL. Pediatr Blood Cancer 2008;51:210–215. © 2008 Wiley‐Liss, Inc.
Comparison of gallium and PET scans at diagnosis and follow‐up of pediatric patients with Hodgkin lymphoma
Authors: Hines‐Thomas Melissa , Kaste Sue C. , Hudson Melissa M. , Howard Scott C. , Liu Wei A. , Wu Jianrong , Kun Larry E. , Shulkin Barry L. , Krasin Matthew J. , Metzger Monika L. 
Published: April 2008

AbstractBackgroundPositron emission tomography (PET) and gallium scans facilitate diagnosis and staging, evaluation of response to therapy, and monitoring for relapse in Hodgkin lymphoma (HL), but have not been compared in pediatric HL.ProcedureWe performed concurrent PET and gallium scans on 44 pediatric HL patients at diagnosis, early response, off chemotherapy, and off‐therapy evaluations. PET and gallium scans were compared to each other and to computed tomography (CT) alone to determine whether either modality led to a change in stage or modified the results of the early response evaluation, which was used to determine the radiation dose.ResultsPET upstaged four patients at diagnosis (2 from stage I to II, one II to III, and one III to IV), but did not lead to a change in therapy in any of them. It changed response category in two patients at early response evaluation, leading to a change in radiation dose for 1 patient (25.5 Gy instead of 15 Gy to the spleen). Gallium did not change the stage of treatment for any patient. The negative predictive values for eventual lymphoma relapse of PET and gallium scans at off therapy were 89% and 83%, respectively; the positive predictive value of PET at off therapy is 29%.ConclusionPET appears to be superior to gallium in pediatric HL; future studies will determine the optimal timing of PET to assess early response and the utility of quantitative interpretation of the avidity of specific nodal sites. Pediatr Blood Cancer 2008;51:198–203. © 2008 Wiley‐Liss, Inc.
Methadone analgesia for children with advanced cancer
Authors: Davies Dawn , DeVlaming Deborah , Haines Christina 
Published: April 2008

AbstractBackgroundMethadone is frequently used in the treatment of adults with advanced cancer. A criticism of relevant research is the use of single or fixed doses, which does not reflect use in clinical practice. Literature about use of methadone in the treatment of pediatric patients is limited to case reports. The objective of this study is to describe methadone use as primary opioid analgesic for advanced pediatric cancer over a 6.5‐year period.ProcedureAll 17 patients who received methadone as their primary opioid analgesic through the Northern Alberta Children's Cancer Program from January 2000 to June 2007 were included. Children who received combination opioid therapy were excluded.ResultsRotation to methadone was usually by a complete switch from primary opioid. Conversion ratios of morphine equivalent daily dose (MEDD)/methadone daily dose (TMDD) ranged widely from 1:2 in one patient with sudden pain crisis just prior to death, to 60:1 in a patient who had been treated with opioids for months. Methadone was used for a total of 925 patient‐days. There were no significant adverse events in any patient, and all but one patient remained on methadone until the time of their death. Clinically, the effectiveness of analgesia clearly improved at time of conversion in 16 patients.ConclusionWith close monitoring, methadone therapy can be done safely in pediatric oncology patient populations in both inpatient and outpatient settings. Our experience suggests improvement in analgesia with the use of methadone, with 16 patients remaining on methadone until they died. Pediatr Blood Cancer 2008;51:393–397. © 2008 Wiley‐Liss, Inc.