bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium time course using 23Na MRI in reversible focal brain ischemia in the monkey
Authors: LaVerde George C. , Jungreis Charles A. , Nemoto Edwin , Boada Fernando E. 
Published: June 2009

AbstractPurposeTo demonstrate the use of sodium MRI for measuring the time course of tissue sodium concentration (TSC) in a nonhuman primate model of reversible focal brain ischemia.Materials and MethodsReversible endovascular focal brain ischemia was induced in nonhuman primates (n = 4), and sodium MRI was performed on a 3 Tesla scanner for monitoring changes in TSC during both the middle cerebral artery (MCA) occlusion and MCA reperfusion portions of the experiment.ResultsThe TSC increased linearly in the ischemic tissue during MCA occlusion (ranging from a mean TSC increase of 5.44%/h to 7.15%/h across the four subjects), and then there was a statistically significant change from a positive TSC slope during MCA occlusion to a TSC slope after MCA reperfusion that was not statistically different from zero. The linear increase in sodium MRI during brain ischemia was used to estimate the stroke onset time to within 0.45 h in each of the four subjects (with a maximum 95% confidence interval of ± 1.147 h).ConclusionThe data indicate that sodium MRI increases linearly during brain ischemia, and that this increase is stopped by tissue reperfusion within 5.4 h after stroke onset. J. Magn. Reson. Imaging 2009;30:219–223. © 2009 Wiley‐Liss, Inc.
Improving computation of cardiovascular relative pressure fields from velocity MRI
Authors: Ebbers Tino , Farnebäck Gunnar 
Published: June 2009

AbstractPurposeTo evaluate a multigrid‐based solver for the pressure Poisson equation (PPE) with Galerkin coarsening, which works directly on the specified domain, for the computation of relative pressure fields from velocity MRI data.Materials and MethodsWe compared the proposed structure‐defined Poisson solver to other popular Poisson solvers working on unmodified rectangular and modified quasirectangular domains using synthetic and in vitro phantoms in which the mathematical solution of the pressure field is known, as well as on in vivo MRI velocity measurements of aortic blood flow dynamics.ResultsAll three PPE solvers gave accurate results for convex computational domains. Using a rectangular or quasirectangular domain on a more complicated domain, like a c‐shape, revealed a systematic underestimation of the pressure amplitudes, while the proposed PPE solver, working directly on the specified domain, provided accurate estimates of the relative pressure fields.ConclusionPopular iterative approaches with quasirectangular computational domains can lead to significant systematic underestimation of the pressure amplitude. We suggest using a multigrid‐based PPE solver with Galerkin coarsening, which works directly on the structure‐defined computational domain. This solver provides accurate estimates of the relative pressure fields for both simple and complex geometries with additional significant improvements with respect to execution speed. J. Magn. Reson. Imaging 2009;30:54–61. © 2009 Wiley‐Liss, Inc.
Multicenter validation of the magnetic resonance t2* technique for segmental and global quantification of myocardial iron
Authors: Ramazzotti Anna , Pepe Alessia , Positano Vincenzo , Rossi Giuseppe , De Marchi Daniele , Brizi Maria Gabriella , Luciani Antongiulio , Midiri Massimo , Sallustio Giuseppina , Valeri Gianluca , Caruso Vincenzo , Centra Michele , Cianciulli Paolo , De Sanctis Vincenzo , Maggio Aurelio , Lombardi Massimo 
Published: June 2009

AbstractPurposeTo assess the transferability of the magnetic resonance imaging (MRI) multislice multiecho T2* technique for global and segmental measurement of iron overload in thalassemia patients.Materials and MethodsMultiecho T2* sequences were installed on six MRI scanners. Five healthy subjects (n = 30) were scanned at each site; five thalassemia major (TM) patients were scanned at the reference site and were rescanned locally (n = 25) within 1 month. T2* images were analyzed using previously validated software.ResultsT2* values of healthy subjects showed intersite homogeneity. On TM patients, for global heart T2* values the correlation coefficient was 0.97, coefficients of variation (CoVs) ranged from 0.04–0.12, and intraclass coefficients (ICCs) ranged from 0.94–0.99. The mean CoV and ICC for segmental T2* distribution were 0.198 and 88, respectively.ConclusionThe multislice multiecho T2* technique is transferable among scanners with good reproducibility. J. Magn. Reson. Imaging 2009;30:62–68. © 2009 Wiley‐Liss, Inc.
Improved myelin water quantification using spatially regularized non‐negative least squares algorithm
Authors: Hwang Dosik , Du Yiping P. 
Published: June 2009

AbstractPurposeTo improve the myelin water quantification in the brain in the presence of measurement noise and to increase the visibility of small focal lesions in myelin‐water‐fraction (MWF) maps.Materials and MethodsA spatially regularized non‐negative least squares (srNNLS) algorithm was developed for robust myelin water quantification in the brain. The regularization for the conventional NNLS algorithm was expanded into the spatial domain in addition to the spectral domain. Synthetic data simulations were performed to study the effectiveness of this new algorithm. Experimental free‐induction‐decay measurements were obtained using a multi‐gradient‐echo pulse sequence and MWF maps were estimated using the srNNLS algorithm. The results were compared with other conventional methods.ResultsA substantial decrease in MWF variability was observed in both simulations and experimental data when the srNNLS algorithm was applied. As a result, false lesions in the MWF maps disappeared and the visibility of small focal lesions improved greatly. On average, the contrast‐to‐noise ratio for focal lesions was improved by a factor of 2.ConclusionThe MWF variability due to the measurement noise can be substantially reduced and the detection of small focal lesions can be improved by using the srNNLS algorithm. J. Magn. Reson. Imaging 2009;30:203–208. © 2009 Wiley‐Liss, Inc.
DCE‐MRI pixel‐by‐pixel quantitative curve pattern analysis and its application to osteosarcoma
Authors: Guo Jun‐Yu , Reddick Wilburn E. 
Published: June 2009

AbstractPurposeTo present a novel curve pattern analysis (CPA) method to characterize and quantify signal curves from the dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) data without any prerequisites such as arterial input function (AIF) or T1 measurement.Materials and MethodsCPA parameters represent characteristics of the scaled DCE signal curve. Simulations were performed to investigate the dependence of CPA parameters on T1, TR, and flip angle. In vivo studies were performed on five pediatric patients with osteosarcoma. Parametric maps were generated using the CPA method and a pharmacokinetic model‐based method for comparison.ResultsSimulations show that CPA parameters varied less than 2% when T1 changed from 300 msec to 1500 msec, and less than 10% when the flip angle changed from 30° to 40°. Various curve patterns can be qualitatively identified and recognized from CPA parameter maps. Simulation and in vivo studies showed that the CPA parameter had a strong correlation with kep, with correlation coefficients of 0.9983 in the simulation and 0.95 in the in vivo studies.ConclusionA novel CPA method is presented. Simulations and in vivo studies showed that the CPA method provides a feasible alternative to quantifying DCE‐MRI studies with possibly higher repeatability by minimizing variations potentially induced by AIF and T1 estimations and model dependence. J. Magn. Reson. Imaging 2009;30:177–184. © 2009 Wiley‐Liss, Inc.
Three‐dimensional analysis of segmental wall shear stress in the aorta by flow‐sensitive four‐dimensional‐MRI
Authors: Frydrychowicz Alex , Stalder Aurélien F. , Russe Maximilian F. , Bock Jelena , Bauer Simon , Harloff Andreas , Berger Alexander , Langer Mathias , Hennig Jürgen , Markl Michael 
Published: June 2009

AbstractPurposeTo assess the distribution and regional differences of flow and vessel wall parameters such as wall shear stress (WSS) and oscillatory shear index (OSI) in the entire thoracic aorta.Materials and MethodsThirty‐one healthy volunteers (mean age = 23.7 ± 3.3 years) were examined by flow‐sensitive four‐dimensional (4D)‐MRI at 3T. For eight retrospectively positioned 2D analysis planes distributed along the thoracic aorta, flow parameters and vectorial WSS and OSI were assessed in 12 segments along the vascular circumference.ResultsMean absolute time‐averaged WSS ranged between 0.25 ± 0.04 N/m2 and 0.33 ± 0.07 N/m2 and incorporated a substantial circumferential component (–0.05 ± 0.04 to 0.07 ± 0.02 N/m2). For each analysis plane, a segment with lowest absolute WSS and highest OSI was identified which differed significantly from mean values within the plane (P < 0.05). The distribution of atherogenic low WSS and high OSI closely resembled typical locations of atherosclerotic lesions at the inner aortic curvature and supraaortic branches.ConclusionThe normal distribution of vectorial WSS and OSI in the entire thoracic aorta derived from flow‐sensitive 4D‐MRI data provides a reference constituting an important perquisite for the examination of patients with aortic disease. Marked regional differences in absolute WSS and OSI may help explaining why atherosclerotic lesions predominantly develop and progress at specific locations in the aorta. J. Magn. Reson. Imaging 2009;30:77–84. © 2009 Wiley‐Liss, Inc.
Study of reproducibility of human arterial plaque reconstruction and its effects on stress analysis based on multispectral in vivo magnetic resonance imaging
Authors: Gao Hao , Long Quan , Graves Martin , Gillard Jonathan H. , Li Zhi‐Yong 
Published: June 2009

AbstractPurposeTo quantify the uncertainties of carotid plaque morphology reconstruction based on patient‐specific multispectral in vivo magnetic resonance imaging (MRI) and their impacts on the plaque stress analysis.Materials and MethodsIn this study, three independent investigators were invited to reconstruct the carotid bifurcation with plaque based on MR images from two subjects to study the geometry reconstruction reproducibility. Finite element stress analyses were performed on the carotid bifurcations, as well as the models with artificially modified plaque geometries to mimic the image segmentation uncertainties, to study the impacts of the uncertainties to the stress prediction.ResultsPlaque reconstruction reproducibility was generally high in the study. The uncertainties among interobservers are around one or the subpixel level. It also shows that the predicted stress is relatively less sensitive to the arterial wall segmentation uncertainties, and more affected by the accuracy of lipid region definition. For a model with lipid core region artificially increased by adding one pixel on the lipid region boundary, it will significantly increase the maximum Von Mises Stress in fibrous cap (>100%) compared with the baseline model for all subjects.ConclusionThe current in vivo MRI in the carotid plaque could provide useful and reliable information for plaque morphology. The accuracy of stress analysis based on plaque geometry is subject to MRI quality. The improved resolution/quality in plaque imaging with newly developed MRI protocols would generate more realistic stress predictions. J. Magn. Reson. Imaging 2009;30:85–93. © 2009 Wiley‐Liss, Inc.
Impact of cerebrospinal fluid contamination on brain metabolites evaluation with 1H‐MR spectroscopy: A single voxel study of the cerebellar vermis in patients with degenerative ataxias
Authors: Guerrini Laura , Belli Giacomo , Mazzoni Lorenzo , Foresti Silvia , Ginestroni Andrea , Della Nave Riccardo , Diciotti Stefano , Mascalchi Mario 
Published: June 2009

AbstractPurposeTo investigate the impact of cerebrospinal fluid (CSF) contamination on metabolite evaluation in the superior cerebellar vermis with single‐voxel 1H‐MRS in normal subjects and patients with degenerative ataxias.Materials and MethodsTwenty‐nine healthy volunteers and 38 patients with degenerative ataxias and cerebellar atrophy were examined on a 1.5 Tesla scanner. Proton spectra of a volume of interest placed in the superior vermis were acquired using a four TE PRESS technique. We calculated N‐acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, and NAA/Cho ratios, T2 relaxation times and concentrations of the same metabolites using the external phantom method. Finally, concentrations were corrected taking into account the proportion of nervous tissue and CSF, that was determined as Volume Fraction (VF).ResultsIn healthy subjects, a significant difference was observed between metabolite concentrations with and without correction for VF. As compared to controls, patients with ataxias showed significantly reduced NAA/Cr and NAA concentrations, while only corrected Cr concentration was significantly increased. The latter showed an inverse correlation with VF.ConclusionCSF contamination has a not negligible effect on the estimation of brain metabolites. The increase of Cr concentration in patients with cerebellar atrophy presumably reflects the substitutive gliosis which takes place along with loss of neurons. J. Magn. Reson. Imaging 2009;30:11–17. © 2009 Wiley‐Liss, Inc.
Combining spatial and temporal information to explore function‐guide action of acupuncture using fMRI
Authors: Liu Peng , Qin Wei , Zhang Yi , Tian Jie , Bai Lijun , Zhou Guangyu , Liu Jixin , Chen Peng , Dai Jianping , von Deneen Karen M. , Liu Yijun 
Published: June 2009

AbstractPurposeTo investigate the brain response patterns of modulation of GB37 (Guangming) and KI8 (Jiaoxin).Materials and MethodsAn experiment using nonrepeated event‐related fMRI design was carried out on 28 subjects with electroacupuncture stimulation (EAS) at GB37 or KI8 on the left leg. The discrete cosine transform and functional connectivity methods were adopted to detect the differences related with these two acupoints before and after the EAS.ResultsSpatial patterns were distinct for EAS at the two acupoints, and the overlapping brain regions were mainly located in the posterior cingulate cortex (PCC) and precuneus (pC). Two opposite patterns of modulation in the default mode network were detected from the temporal patterns with the overlapping PCC/pC as the region of interest. Furthermore, the specific responses of sustained effects at these acupoints were also identified.ConclusionSpatial and temporal patterns of the sustained effect modulation of GB37 and KI8 were distinct. We suggest these findings may attribute to the functional specificity of a certain acupoint. Moreover, our current results reflect a significant methodological contribution to future acupuncture studies. J. Magn. Reson. Imaging 2009;30:41–46. © 2009 Wiley‐Liss, Inc.
Pilot study of improved lesion characterization in breast MRI using a 3D radial balanced SSFP technique with isotropic resolution and efficient fat‐water separation
Authors: Moran Catherine J. , Kelcz Frederick , Jung Youngkyoo , Brodsky Ethan K. , Fain Sean B. , Block Walter F. 
Published: June 2009

AbstractPurposeTo assess a 3D radial balanced steady‐state free precession (SSFP) technique that provides submillimeter isotropic resolution and inherently registered fat and water image volumes in comparison to conventional T2‐weighted RARE imaging for lesion characterization in breast magnetic resonance imaging (MRI).Materials and Methods3D projection SSFP (3DPR‐SSFP) combines a dual half‐echo radial k‐space trajectory with a linear combination fat/water separation technique (linear combination SSFP). A pilot study was performed in 20 patients to assess fat suppression and depiction of lesion morphology using 3DPR‐SSFP. For all patients fat suppression was measured for the 3DPR‐SSFP image volumes and depiction of lesion morphology was compared against corresponding T2‐weighted fast spin echo (FSE) datasets for 15 lesions in 11 patients.ResultsThe isotropic 0.63 mm resolution of the 3DPR‐SSFP sequence demonstrated improved depiction of lesion morphology in comparison to FSE. The 3DPR‐SSFP fat and water datasets were available in a 5‐minute scan time while average fat suppression with 3DPR‐SSFP was 71% across all 20 patients.Conclusion3DPR‐SSFP has the potential to improve the lesion characterization information available in breast MRI, particularly in comparison to conventional FSE. A larger study is warranted to quantify the effect of 3DPR‐SSFP on specificity. J. Magn. Reson. Imaging 2009;30:135–144. © 2009 Wiley‐Liss, Inc.
Temporal sampling requirements for reference region modeling of DCE‐MRI data in human breast cancer
Authors: Planey Catherine R. , Welch E. Brian , Xu Lei , Chakravarthy A. Bapsi , Gatenby J. Christopher , Freehardt Darla , Mayer Ingrid , Meszeoly Ingrid , Kelley Mark , Means‐Powell Julie , Gore John C. , Yankeelov Thomas E. 
Published: June 2009

AbstractPurposeTo assess the temporal sampling requirements needed for quantitative analysis of dynamic contrast‐enhanced MRI (DCE‐MRI) data with a reference region (RR) model in human breast cancer.Materials and MethodsSimulations were used to study errors in pharmacokinetic parameters (Ktrans and ve) estimated by the RR model using six DCE‐MRI acquisitions over a range of pharmacokinetic parameter values, arterial input functions, and temporal samplings. DCE‐MRI data were acquired on 12 breast cancer patients and parameters were estimated using the native resolution data (16.4 seconds) and compared to downsampled 32.8‐second and 65.6‐second data.ResultsSimulations show that, in the majority of parameter combinations, the RR model results in an error less than 20% in the extracted parameters with temporal sampling as poor as 35.6 seconds. The experimental results show a high correlation between Ktrans and ve estimates from data acquired at 16.4‐second temporal resolution compared to the downsampled 32.8‐second data: the slope of the regression line was 1.025 (95% confidence interval [CI]: 1.021, 1.029), Pearson's correlation r = 0.943 (95% CI: 0.940, 0.945) for Ktrans, and 1.023 (95% CI: 1.021. 1.025), r = 0.979 (95% CI: 0.978, 0.980) for ve. For the 64‐second temporal resolution data the results were: 0.890 (95% CI: 0.894, 0.905), r = 0.8645, (95% CI: 0.858, 0.871) for Ktrans, and 1.041 (95% CI: 1.039, 1.043), r = 0.970 (95% CI: 0.968, 0.971) for ve.ConclusionRR analysis allows for a significant reduction in temporal sampling requirements and this lends itself to analyze DCE‐MRI data acquired in practical situations. J. Magn. Reson. Imaging 2009;30:121–134. © 2009 Wiley‐Liss, Inc.
A diffusion tensor imaging group study of the spinal cord in multiple sclerosis patients with and without T2 spinal cord lesions
Authors: Van Hecke Wim , Nagels Guy , Emonds Griet , Leemans Alexander , Sijbers Jan , Van Goethem Johan , Parizel Paul M. 
Published: June 2009

AbstractPurposeTo examine the T2‐normal appearing spinal cord of patients with multiple sclerosis (MS) using diffusion tensor imaging.Materials and MethodsDiffusion tensor images of the spinal cord were acquired from 21 healthy subjects, 11 MS patients with spinal cord lesions, and 10 MS patients without spinal cord lesions on the T2‐weighted MR images. Different diffusion measures were evaluated using both a region of interest (ROI) ‐based and a diffusion tensor tractography‐based segmentation approach.ResultsIt was observed that the FA, the transverse diffusivity λ⟂, and the ratio of the longitudinal and transverse diffusivities (λ∥/λ ⟂) were significantly lower in the spinal cord of MS patients with spinal cord lesions compared with the control subjects using both the ROI method (P = 0.014, P = 0.028, and P = 0.039, respectively) and the tractography‐based approach (P = 0.006, P = 0.037, and P = 0.012, respectively). For both image analysis methods, the FA and the λ ∥/λ ⟂ values were significantly different between the control group and the MS patient group without T2 spinal cord lesions (P = 0.013).ConclusionOur results suggest that the spinal cord may still be affected by MS, even when lesions are not detected on a conventional MR scan. In addition, we demonstrated that diffusion tensor tractography is a robust tool to analyze the spinal cord of MS patients. J. Magn. Reson. Imaging 2009;30:25–34. © 2009 Wiley‐Liss, Inc.
Added value of diffusion‐weighted imaging in the MRI assessment of perilesional tumor recurrence after chemoembolization of hepatocellular carcinomas
Authors: Yu Jeong‐Sik , Kim Joo Hee , Chung Jae‐Joon , Kim Ki Whang 
Published: June 2009

AbstractPurposeTo investigate the additional value of diffusion‐weighted imaging (DWI) in the MRI assessment of perilesionally recurrent hepatocellular carcinomas (HCCs) after transcatheter arterial chemoembolization (TACE).Materials and MethodsFor gadopentetate dimeglumine‐enhanced multiphasic dynamic images with precontrast T1‐ and T2‐weighted images of 23 patients treated with TACE, two radiologists independently sorted the confidence levels for the presence of a viable tumor in the vicinity of the treated lesions into five grades. In another session, images from DWI (b factor = 50, 400, and 800 s/mm2) were added to the previously reviewed images and the same radiologists sorted the confidence levels.ResultsA total of 26 lesions (0.7–3.5 cm) from 16 patients were confirmed to be perilesional recurrences of HCC. The area under the receiver operating characteristic curve (Az) for the second interpretation session (0.826) was not significantly different (P = 0.299) from that of the first session (0.859). The overall sensitivity was increased from 85% to 92%, but the specificity decreased from 65% to 50% after adding DWI.ConclusionThe addition of DWI has the potential to improve sensitivity, but not the overall diagnostic accuracy, in the assessment of perilesional recurrence of HCCs after chemoembolization. J. Magn. Reson. Imaging 2009;30:153–160. © 2009 Wiley‐Liss, Inc.
Automated assessment of whole‐body adipose tissue depots from continuously moving bed MRI: A feasibility study
Authors: Kullberg Joel , Johansson Lars , Ahlström Håkan , Courivaud Frederic , Koken Peter , Eggers Holger , Börnert Peter 
Published: June 2009

AbstractPurposeTo present an automated algorithm for segmentation of visceral, subcutaneous, and total volumes of adipose tissue depots (VAT, SAT, TAT) from whole‐body MRI data sets and to investigate the VAT segmentation accuracy and the reproducibility of all depot assessments.Materials and MethodsRepeated measurements were performed on 24 volunteer subjects using a 1.5 Tesla clinical MRI scanner and a three‐dimensional (3D) multi‐gradient‐echo sequence (resolution: 2.1 × 2.1 × 8 mm3, acquisition time: 5 min 15 s). Fat and water images were reconstructed, and fully automated segmentation was performed. Manual segmentation of the VAT reference was performed by an experienced operator.ResultsStrong correlation (R = 0.999) was found between the automated and manual VAT assessments. The automated results underestimated VAT with 4.7 ± 4.4%. The accuracy was 88 ± 4.5% and 7.6 ± 5.7% for true positive and false positive fractions, respectively. Coefficients of variation from the repeated measurements were: 2.32 % ± 2.61%, 2.25% ± 2.10%, and 1.01% ± 0.74% for VAT, SAT, and TAT, respectively.ConclusionAutomated and manual VAT results correlated strongly. The assessments of all depots were highly reproducible. The acquisition and postprocessing techniques presented are likely useful in obesity related studies. J. Magn. Reson. Imaging 2009;30:185–193. © 2009 Wiley‐Liss, Inc.