bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of intravenous gadolinium administration and flip angle on the assessment of liver fat signal fraction with opposed‐phase and in‐phase imaging
Authors: Yokoo Takeshi , Collins Julie M. , Hanna Robert F. , Bydder Mark , Middleton Michael S. , Sirlin Claude B. 
Published: June 2008

AbstractPurposeTo assess the effects of intravenous gadolinium (Gd) and flip angle (FA) on liver fat quantification by opposed‐phase (OP) and in‐phase (IP) imaging.Materials and MethodsOur Institutional Review Board (IRB) approved this Health Insurance Portability and Accountability Act (HIPAA)‐compliant, retrospective, clinical study. We identified 79 patients in whom abdominal OP and IP gradient‐echoes were obtained at 1.5T before and after Gd administration. All 79 patients were imaged at high FA (≥70°); 57 were also imaged at low FA (≤20°). Fat signal fraction (FSF) was calculated from pre‐ and post‐Gd liver images for each subject and FA using the formula, FSF = (SIP – SOP)/2SIP, where SIP and SOP are the OP and IP signal intensities, respectively. The dataset pairs (pre‐Gd vs. post‐Gd; high‐FA vs. low‐FA) were compared using linear regression analysis.ResultsBefore Gd, FSF was significantly greater at high FA than at low FA, with regression parameters (slope/intercept) of 1.27*/0.02*, where * indicates P value <0.01. After Gd, FSF was similar at high and low FA (0.99/–0.00). Gd administration caused an FA‐dependent reduction in FSF, larger at high FA (0.68*/–0.03*) than at low FA (0.94, –0.01*).ConclusionFSF by OP‐IP imaging is highly dependent on FA before Gd, but this dependency is eliminated after administration of Gd. Gd appears to minimize the effect of T1‐weighting and may improve the accuracy of liver fat quantification. J. Magn. Reson. Imaging 2008;28:246–251. © 2008 Wiley‐Liss, Inc.
Dynamic contrast‐enhanced magnetic resonance imaging: A useful tool for characterizing ovarian epithelial tumors
Authors: Thomassin‐Naggara Isabelle , Daraï Emile , Cuenod Charles A , Rouzier Roman , Callard Patrice , Bazot Marc 
Published: June 2008

AbstractPurposeTo evaluate the utility of dynamic contrast enhancement (DCE) MRI for distinguishing among benign, borderline and invasive epithelial ovarian tumors.Materials and MethodsWe analyzed preoperative MRI studies of 37 patients with ovarian epithelial tumors (10 benign, 11 borderline, and 16 invasive). A DCE‐MRI sequence was acquired and regions of interest (ROIs) were drawn in the ovarian tumors and adjacent myometrium. A total of three patterns of enhancement were defined. Dynamic data were parameterized using mathematical models that included the enhancement amplitude (EA), the time of half rising (THR), and the maximal slope (MS). Using myometrium as the internal reference, ratios of EA (EAr), THR (THRr), MS (MSr), and initial area under the curve for 60 seconds after injection (IAUC60 ratio) were determined.ResultsMorphological criteria such as septa, papillary projection, solid portion, and T2‐weighted MR signal intensity of solid tissue were useful for discriminating invasive from noninvasive ovarian tumors (P = 0.01, P = 0.02, P = 0.002, and P < 0.0001 respectively) but not for discriminating benign from borderline tumors. Curve type 3 was specific for invasive ovarian tumors. EAr, MSr, and IAUC60 ratio were higher for invasive than for benign (P < 0.0001) and borderline tumors (P = 0.005, P = 0.002, and P = 0.001, respectively). The IAU60 ratio was the most relevant factor for discriminating benign from borderline and invasive tumors. MSr and IAU60 ratio could be combined to generate a decision tree with 81% accuracy.ConclusionDCE‐MRI is a useful tool for characterizing epithelial ovarian tumors. J. Magn. Reson. Imaging 2008;28:111–120. © 2008 Wiley‐Liss, Inc.
A regularized two‐tensor model fit to low angular resolution diffusion images using basis directions
Authors: Sotiropoulos Stamatios N. , Bai Li , Morgan Paul S. , Auer Dorothee P. , Constantinescu Cris S. , Tench Christopher R. 
Published: June 2008

AbstractPurposeTo resolve and regularize orientation estimates for two crossing fibers from images acquired with conventional diffusion tensor imaging (DTI) sampling schemes.Materials and MethodsPartial volume causes artifacts in DTI. Given that routine use of high angular resolution diffusion imaging (HARDI) is still tentative, a regularized two‐tensor model to resolve fiber crossings from conventional DTI datasets is presented. To overcome the problems of fitting multiple tensors, a model that exploits the planar diffusion profile in regions with fiber crossings is utilized. A regularization scheme is applied to reduce noise artifacts, which can be significant due to the relatively low number of acquired images. A set of basis directions is used to convert the two tensor model to many models of lower dimensionality. Relaxation labeling is utilized to select from amongst these models those that preserve continuity of orientations across neighbors. Revised fractional anisotropy (FA) and mean diffusivity (MD) values are computed.ResultsSpatial regularization improves the orientation estimates of the two‐tensor model in simulations and in human data and estimates agree well with a priori anatomical knowledge.ConclusionOrientational, anisotropy, and diffusivity information can be resolved in regions of two fiber crossings using full brain coverage scans acquired in less than six minutes. J. Magn. Reson. Imaging 2008;28:199–209. © 2008 Wiley‐Liss, Inc.
Abnormalities in T2‐weighted cardiovascular magnetic resonance images of hypertrophic cardiomyopathy: Regional distribution and relation to late gadolinium enhancement and severity of hypertrophy
Authors: Abdel‐Aty Hassan , Cocker Myra , Strohm Oliver , Filipchuk Neil , Friedrich Matthias G. 
Published: June 2008

AbstractPurposeTo explore if focal T2 abnormalities accompany late gadolinium enhancement (LGE) lesions in hypertrophic cardiomyopathy (HCM).Materials and MethodsAll studies were performed under the guidelines of the local ethics committee, which approved the study, and a written informed consent was obtained from each subject. We studied 27 patients (24 males, 51 ± 18 years) with HCM and evidence for myocardial injury as defined by LGE. The following sequences were performed: steady‐state free precession (SSFP) (ventricular volumes, mass, and function), T2‐weighted triple inversion‐recovery spin‐echo and inversion‐recovery gradient‐echo 10 minutes after intravenous (IV) gadolinium‐DTPA (late enhancement).ResultsFocal high T2 signal intensity (SI) frequently matching areas of LGE was observed in nine patients (33%). The presence of these abnormalities correlated with more severe left ventricular hypertrophy (1.5 ± 0.6 vs. 1.0 ± 0.4 g/cm; P < 0.05).ConclusionIn this observational study, we identified focal T2 abnormalities in a subgroup of HCM patients. T2 abnormalities are associated with severe left ventricular hypertrophy. This may provide new insights into the mechanisms of focal irreversible injury in HCM and help in managing these patients. J. Magn. Reson. Imaging 2008;28:242–245. © 2008 Wiley‐Liss, Inc.
T2‐ and diffusion‐maps reveal diurnal changes of intervertebral disc composition: An in vivo MRI study at 1.5 Tesla
Authors: Ludescher Burkhard , Effelsberg Julia , Martirosian Petros , Steidle Günter , Markert Bernd , Claussen Claus , Schick Fritz 
Published: June 2008

AbstractPurposeTo investigate the lumbar intervertebral discs (IVDs) by MRI in the morning and evening after a diurnal load cycle. Changes in MR characteristics (T2‐weighted imaging, T2‐ and apparent diffusion coefficient [ADC] ‐mapping) during the course of the day were visualized and analyzed visually and quantitatively. The length of the lumbar spine was measured in between the lower anterior edge of Th12 and the upper anterior edge of S1. T2 changes and diffusion characteristics of the vertebral disc tissue were investigated with a higher spatial resolution than in former studies.Materials and MethodsIn six males, lumbar IVDs were investigated in the morning and evening. T2‐maps and ADC maps were generated. Data were analyzed by selecting regions of interest (ROI) in the annulus fibrosus (AF), nucleus pulposus (NP), and an intermediate area.ResultsFrom morning to evening, T2 decreased in the center of the NP (−7.9%; P = 0.001) and the intermediate voxels (−6.4%; P < 0.0005). T2 increased (8.5%; P < 0.048) in the AF. ADC decreased in the AF (−5.2%; P = 0.007) and the intermediate ROIs (−2.2%; P = 0.004). There was no significant change of ADC in the NP (−1.6%; P = 0.242).ConclusionT2 and diffusion (ADC) changes of IVDs in humans were investigated with a spatial differentiation between NP and AF. T2 and ADC turned out to be sensitive parameters in investigating changes in the MR characteristics of the IVD matrix during a day. Highly resolved MR imaging and parameter mapping is expected to be an interesting tool in characterizing structural changes in the vertebral disc architecture in an early stage of degeneration. J. Magn. Reson. Imaging 2008;28:252–257. © 2008 Wiley‐Liss, Inc.
MRI phase contrast velocity and flow errors in turbulent stenotic jets
Authors: O'Brien Kieran R. , Cowan Brett R. , Jain Manali , Stewart Ralph A.H. , Kerr Andrew J. , Young Alistair A. 
Published: June 2008

AbstractPurposeTo clarify the use of MRI phase contrast (PC), as an alternative to Doppler echocardiography, when measuring high‐velocity turbulent jets associated with stenotic valvular disease.Materials and MethodsIn vivo PC aortic stroke volume (SV) was compared with ventricular SV in 31 patients with moderate to severe aortic stenosis (AS). Two in vitro pipe experiments were conducted to evaluate errors in steady stenotic and nonstenotic turbulent flows.ResultsThe average in vivo error in SV was −24% in the left‐ventricular (LV) outflow tract (LVOT) and −41% in the aortic root. Errors were most prominent in patients with the highest Doppler peak velocities. In vitro nonstenotic flow experiments showed accurate flow measurement with an average error of 1.8%. Significant errors were found in the in vitro stenotic flow, which reduced with shorter echo times (TE): average error −166/−67/−25/−13/−8.8% for TEs of 4.8/4.0/3.3/2.2/2.0 msec. In both the in vivo and in vitro stenotic experiments the errors were associated with signal loss in the flow‐compensated magnitude image.ConclusionSignal loss is associated with flow errors in stenotic jets. Current clinically available PC pulse sequences with TE >2 msec may not accurately quantify flow for severe lesions. J. Magn. Reson. Imaging 2008;28:210–218. © 2008 Wiley‐Liss, Inc.
Improved slice selection for R2* mapping during cryoablation with eddy current compensation
Authors: Lu Aiming , Daniel Bruce L. , Pauly John M. , Butts Pauly Kim 
Published: June 2008

AbstractPurposeTo improve the slice profile and image quality of R2* mapping in the iceball during cryoablation with ultrashort echo time (UTE) imaging by compensating for eddy currents induced by the selective gradient when half‐pulse radiofrequency (RF) excitation is employed to achieve UTEs.Materials and MethodsA method to measure both B0 and linear eddy currents simultaneously is first presented. This is done with a least‐square fitting process on calibration data collected on a phantom. Eddy currents during excitation are compensated by redesigning the RF pulse and the selective gradient accordingly, while that resultant from the readout gradient are compensated for during image reconstruction. In vivo data were obtained continuously during the cryoablation experiments to calculate the R2* values in the iceball and to correlate them with the freezing process.ResultsImage quality degradation due to eddy currents is significantly reduced with the proposed approaches. R2* maps of iceball throughout the cryoablation experiments were achieved with improved quality.ConclusionThe proposed approaches are effective for compensating eddy currents during half‐pulse RF excitation as well as readout. TEs as short as 100 μsec were obtained, allowing R2* maps to be obtained from frozen tissues with improved quality. J. Magn. Reson. Imaging 2008;28:190–198. © 2008 Wiley‐Liss, Inc.
Fast and optimized T1 mapping technique for the noninvasive quantification of gastric secretion
Authors: Treier Reto , Steingoetter Andreas , Goetze Oliver , Fox Mark , Fried Michael , Schwizer Werner , Boesiger Peter 
Published: June 2008

AbstractPurposeTo evaluate the noninvasive quantification of gastric secretion volume after administration of a labeled viscous glucose solution by fast T1 mapping.Materials and MethodsT1 values of a series of labeled and diluted glucose solutions were measured in vitro to characterize the interrelationship between T1 and contrast agent concentration (CGd) as well as the dependency of relaxivity and reference T1 (T10) on the macromolecular concentration. Abdominal T1 mapping in five healthy volunteers of different body mass index was performed after filling an intragastric balloon with a labeled and diluted glucose solution. In additional ex vivo experiments, T1 values of gastric (GJ) and duodenal juice (DJ) and 0.1 N HCl solution were determined.ResultsA linear relationship between relaxivity and macromolecular concentration and between T10 and macromolecular concentration was found. The in vitro T1–CGd calibration curve was successfully validated in all volunteers. T1 values of GJ, DJ, and HCl (2939 msec vs. 2858 msec vs. 2760 msec) were close to the T1 of water (≈3000 msec).ConclusionThe presented method allows one to noninvasively quantify the spatial distribution of gastric secretory products in the human stomach and provides a valuable tool for evaluating the efficacy of drugs to stimulate/inhibit gastric secretion. J. Magn. Reson. Imaging 2008;28:96–102. © 2008 Wiley‐Liss, Inc.
Reducing morphological variability of the cervical carotid artery in serial magnetic resonance imaging using a head and neck immobilization device
Authors: Chapman Brian E. , Minalga Emilee S. , Brown Christopher , Roberts John A. , Hadley J. Rock 
Published: June 2008

AbstractPurposeTo evaluate how well a head and neck immobilization device performed in reducing lumen morphology variability in repeated MR imaging of the carotid artery.Materials and MethodsQuantitative measures of lumen and plaque characteristics may be important for longitudinal management of carotid atherosclerotic disease. However, quantitative measurements of the carotid artery are limited by their dependence on patient positioning, which can be quite variable. We created a head and neck immobilization device to reduce the variability of patient positioning during MR imaging of the carotid artery. In this article we describe the design and use of the immobilization device and assess how well its use reduced variability in vascular orientation and measurements of the carotid lumen cross‐sectional area. Evaluation was based on 15 subjects who were repeatedly imaged without the immobilization device and 14 subjects who were repeatedly imaged with the device.ResultsUse of the immobilization device decreased the orientation variability from 9.1° to 5.3° (P = 0.0006) and the variability (defined as the standard deviation divided by the mean) of the cross‐sectional area decreased from 0.24 to 0.18 (P = 0.04).ConclusionUsing the immobilization device effectively reduces variability in repeated imaging of the carotid arteries. J. Magn. Reson. Imaging 2008;28:258–262. © 2008 Wiley‐Liss, Inc.
Quantitative myocardial perfusion imaging using different autocalibrated parallel acquisition techniques
Authors: Weber Stefan , Kronfeld Andrea , Kunz R. Peter , Muennemann Kerstin , Horstick Georg , Kreitner Karl‐Friedrich , Schreiber Wolfgang G. 
Published: June 2008

AbstractPurposeTo compare three different autocalibrated parallel acquisition techniques (PAT) for quantitative and semiquantitative myocardial perfusion imaging.Materials and MethodsSeven healthy volunteers underwent myocardial first‐pass perfusion imaging at rest using an SR‐TrueFISP pulse sequence without PAT and while using GRAPPA, mSENSE, and TSENSE. signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), normalized upslopes (NUS), and myocardial blood flow (MBF) were calculated. Artifacts, image noise, and overall image quality were qualitatively assessed. Furthermore, the relation between signal intensity (SI) and contrast medium (CM) concentration was determined in phantoms.ResultsUsing PAT the linear range of the SR‐TrueFISP sequence was increased about 40%. All three PAT methods introduced significant loss in SNR and CNR. GRAPPA yielded slightly better values then mSENSE and TSENSE. Both SENSE techniques introduced significantly residual aliasing artifacts. Image noise was increased with all three PAT methods. However, overall image quality was reduced only with mSENSE. Even though GRAPPA yielded smaller NUS values than non‐PAT, mSENSE, and TSENSE, no differences were found in MBF between all applied techniques.ConclusionQuantitative and semiquantitative myocardial perfusion imaging can benefit from PAT due to shorter acquisition times and increased linearity of the pulse sequence. GRAPPA and TSENSE turned out to be well suited for quantitative myocardial perfusion imaging. J. Magn. Reson. Imaging 2008;28:51–59. © 2008 Wiley‐Liss, Inc.
Reproducibility of MRI measurements of right ventricular size and function in patients with normal and dilated ventricles
Authors: Mooij Christiaan F. , de Wit Cornelis J. , Graham Dionne A. , Powell Andrew J. , Geva Tal 
Published: June 2008

AbstractPurposeTo determine the inter‐ and intraobserver reproducibility of cardiac magnetic resonance (CMR)‐derived measurements of right ventricular (RV) mass, volume, and function in patients with normal and dilated ventricles.Materials and MethodsCMR studies of 60 patients in three groups were studied: a normal RV group (N = 20) and two groups with RV dilation—atrial septal defect (ASD) (N = 20) and repaired tetralogy of Fallot (TOF) (N = 20). Two independent observers analyzed each study on two separate occasions. Inter‐ and intraobserver reproducibility of biventricular mass, volume, ejection fraction (EF), and stroke volume (SV) measurements were calculated.ResultsHigh intraclass correlation coefficients (ICC) were found for interobserver (ICC = 0.94–0.99) and intraobserver (ICC = 0.96–0.99) comparisons of RV and left ventricular (LV) mass, volume, and SV measurements. RV and LV EF measurements were less reproducible (ICC = 0.79–0.87). RV mass measurements were significantly less correlated than the respective LV measurements. Small but statistically significant differences in correlation were noted in RV measurements across groups.ConclusionExcept for RV mass, inter‐ and intraobserver reproducibility of RV size and function measurements is high and generally comparable to that in the LV in patients with both normal and dilated RV. J. Magn. Reson. Imaging 2008;28:67–73. © 2008 Wiley‐Liss, Inc.
Assessment of the lung microstructure in patients with asthma using hyperpolarized 3He diffusion MRI at two time scales: Comparison with healthy subjects and patients with COPD
Authors: Wang Chengbo , Altes Talissa A. , Mugler John P. , Miller G. Wilson , Ruppert Kai , Mata Jaime F. , Cates Gordon D. , Borish Larry , de Lange Eduard E. 
Published: June 2008

AbstractPurposeTo investigate short‐ and long‐time‐scale 3He diffusion in asthma.Materials and MethodsA hybrid MRI sequence was developed to obtain coregistered short‐ and long‐time‐scale apparent diffusion coefficient (ADC) maps during a single breath‐hold. The study groups were: asthma (n = 14); healthy (n = 14); chronic obstructive pulmonary disease (COPD) (n = 9). Correlations were made between mean‐ADC and %ADC‐abn (abnormal) (%pixels with ADC > mean +2 SD of healthy) at both time scales and spirometry. Sensitivities were determined using receiver operating characteristic (ROC) analysis.ResultsFor asthmatics, the short‐ and long‐time‐scale group‐mean ADCs were 0.254 ± 0.032 cm2/s and 0.0237 ± 0.0055 cm2/s, respectively, representing a 9% and 27% (P = 0.038 and P = 0.005) increase compared to the healthy group. The group‐mean %ADC‐abn were 6.4% ± 3.7% and 17.5% ± 14.2%, representing a 107% and 272% (P = 0.004 and P = 0.006) increase. For COPD much greater elevations were observed. %ADC‐abn provided better discrimination than mean‐ADC between asthmatic and healthy subjects. In asthmatics ADC did not correlate with spirometry.ConclusionWith long‐time scale 3He diffusion magnetic resonance imaging (MRI) changes in lung microstructure were detected in asthma that more conspicuous regionally than at the short time scale. The hybrid diffusion method is a novel means of identifying small airway disease. J. Magn. Reson. Imaging 2008;28:80–88. © 2008 Wiley‐Liss, Inc.
Feasibility and reproducibility of relaxometry, morphometric, and geometrical measurements of the hip joint with magnetic resonance imaging at 3T
Authors: Carballido‐Gamio Julio , Link Thomas M. , Li Xiaojuan , Han Eric T. , Krug Roland , Ries Michael D. , Majumdar Sharmila 
Published: June 2008

AbstractPurposeTo test the feasibility of in vivo magnetic resonance T1ρ relaxation time measurements of hip cartilage, and quantify the reproducibility of hip cartilage thickness, volume, T2, T1ρ, and size of femoral head measurements.Materials and MethodsThe hip joint of five human healthy volunteers, one subject with mild hip osteoarthritis (OA) and one subject with advanced hip OA, was imaged with magnetic resonance imaging (MRI) at 3T. Hip cartilage thickness, volume, T1ρ, and T2 were quantified, as well as the size of the femoral head. All imaging and analysis procedures were performed twice for the healthy volunteers to assess reproducibility.ResultsIn vivo MR T1ρ measurements of hip cartilage at 3T were feasible as demonstrated by high quality images and relaxation time maps. High levels of reproducibility were obtained for measurements of hip cartilage thickness (CVSD = 2.19%), volume (CVSD = 3.5%), T2 (CVSD = 5.89%), T1ρ (CVSD = 2.03%), and size of femoral head (CVSD = 0.49%). Mean T2 and T1ρ relaxation time values for human healthy subjects were 28.38 (±2.66) msec and 38.72 (±3.84) msec, respectively. Mean T2 and T1ρ relaxation time values for subjects with OA were 34.78 (±8.36) msec and 44.07 (±0.99) msec, respectively. T2 and T1ρ values increased from the deep to the superficial layers.ConclusionQualitative and quantitative results indicate that the MRI techniques presented in this study may be applied clinically to patients with OA of the hip to investigate these parameters at different stages of disease. J. Magn. Reson. Imaging 2008;28:227–235. © 2008 Wiley‐Liss, Inc.