bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the Electrochemical Reactivity of Carbon Nanotubes Paste Electrodes with Different Types of Multiwalled Carbon Nanotubes
Authors: Li Xueling , Ye Jianshan
Published: June 2008

Carbon nanotubes (CNTs) are widely used in electrochemical studies. It is reported that CNTs with different source and dispersed in different agents [1] yield significant difference of electrochemical reactivity. Here we report on the electrochemical performance of CNTs paste electrodes (CNTPEs) prepared by multiwalled carbon nanotubes (MWNTs) with different diameters, lengths and functional groups. The resulting electrodes exhibit remarkable different electrochemical reactivity towards redox molecules such as NADH and K3[Fe(CN)6]. It is found that CNTPEs prepared by MWNTs with 20–30 nm diameter show highest catalysis to NADH oxidation, while CNTPEs prepared by MWNTs with carboxylate groups have best electron‐transfer rate (The peak‐peak separation (ΔEp) is +0.108 V for MWNTs with carboxylate groups, +0.155 V for normal MWNTs, and +0.174 V for short MWNTs) but weak catalysis towards oxidation of NADH owing to the hydrophilicity of carboxylate groups. The electrochemical reactivity depends on the lengths of CNTs to some extent. The ‘long’ CNTs perform better in our study (The oxidation signals of NADH appear below +0.39 V for ‘long’ CNTs and above +0.46 V for the ‘short’ one totally). Readers may get some directions from this article while choose CNTs for electrochemical study.
DNA Stabilization and Hybridization Detection on Porous Silicon Surface by EIS and Total Reflection FT‐IR Spectroscopy
Authors: Vamvakaki Vicky , Chaniotakis Nikos A.
Published: June 2008

Electrochemically etched porous silicon (PSi) is formed and employed as a substrate for the entrapment of oligonucleotides and the subsequent development of stable DNA biosensors. The controlled potential anodic etching of p‐type silicon wafers is optimized in order to obtain a surface layer with pore diameters which are close to those of the adsorbed DNA helix. The stabilization and hybridization of DNA inside the PSi layer is confirmed using ATR‐FTIR. Moreover hybridization is verified by the large and reproducible impedance changes at the interface layer. The developed PSi DNA sensor paves the way for the label‐free detection of oligonucleotide sequences in DNA microarrays and microfabricated PSi field‐effect sensors.
Principles of whole‐body continuously‐moving‐table MRI
Authors: Börnert Peter , Aldefeld Bernd
Published: June 2008

Continuously‐moving‐table (CMT) imaging is a new and promising approach to virtually extend the field‐of‐view (FOV) in currently available MRI systems. It shows high potential to improve a number of applications that require a large FOV, such as whole‐body contrast‐enhanced angiography and contrast‐optimized whole‐body head‐to‐toe imaging. In this work, an overview of the different approaches to CMT imaging is given. Basic principles of two‐ and three‐dimensional (2D and 3D) techniques are discussed, with emphasis on performance and image‐artifact issues. Potential clinical applications and further desirable improvements are outlined. J. Magn. Reson. Imaging 2008;28:1–12. © 2008 Wiley‐Liss, Inc.
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

Purpose

To 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 Methods

Our 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.

Results

Before 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*).

Conclusion

FSF 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

Purpose

To evaluate the utility of dynamic contrast enhancement (DCE) MRI for distinguishing among benign, borderline and invasive epithelial ovarian tumors.

Materials and Methods

We 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.

Results

Morphological 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.

Conclusion

DCE‐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

Purpose

To resolve and regularize orientation estimates for two crossing fibers from images acquired with conventional diffusion tensor imaging (DTI) sampling schemes.

Materials and Methods

Partial 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.

Results

Spatial 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.

Conclusion

Orientational, 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

Purpose

To explore if focal T2 abnormalities accompany late gadolinium enhancement (LGE) lesions in hypertrophic cardiomyopathy (HCM).

Materials and Methods

All 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).

Results

Focal 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).

Conclusion

In 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

Purpose

To 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 Methods

In 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.

Results

From 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).

Conclusion

T2 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

Purpose

To 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 Methods

In 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.

Results

The 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.

Conclusion

Signal 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

Purpose

To 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 Methods

A 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.

Results

Image 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.

Conclusion

The 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

Purpose

To evaluate the noninvasive quantification of gastric secretion volume after administration of a labeled viscous glucose solution by fast T1 mapping.

Materials and Methods

T1 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.

Results

A 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).

Conclusion

The 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

Purpose

To 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 Methods

Quantitative 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.

Results

Use 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).

Conclusion

Using 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

Purpose

To compare three different autocalibrated parallel acquisition techniques (PAT) for quantitative and semiquantitative myocardial perfusion imaging.

Materials and Methods

Seven 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.

Results

Using 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.

Conclusion

Quantitative 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

Purpose

To 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 Methods

CMR 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.

Results

High 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.

Conclusion

Except 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

Purpose

To investigate short‐ and long‐time‐scale 3He diffusion in asthma.

Materials and Methods

A 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.

Results

For 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.

Conclusion

With 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

Purpose

To 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 Methods

The 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.

Results

In 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.

Conclusion

Qualitative 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.
Feasibility of using real‐time MRI to measure joint kinematics in 1.5T and open‐bore 0.5T systems
Authors: Draper Christine E. , Santos Juan M. , Kourtis Lampros C. , Besier Thor F. , Fredericson Michael , Beaupre Gary S. , Gold Garry E. , Delp Scott L.
Published: June 2008

Purpose

To test the feasibility and accuracy of measuring joint motion with real‐time MRI in a 1.5T scanner and in a 0.5T open‐bore scanner and to assess the dependence of measurement accuracy on movement speed.

Materials and Methods

We developed an MRI‐compatible motion phantom to evaluate the accuracy of tracking bone positions with real‐time MRI for varying movement speeds. The measurement error was determined by comparing phantom positions estimated from real‐time MRI to those measured using optical motion capture techniques. To assess the feasibility of measuring in vivo joint motion, we calculated 2D knee joint kinematics during knee extension in six subjects and compared them to previously reported measurements.

Results

Measurement accuracy decreased as the phantom's movement speed increased. The measurement accuracy was within 2 mm for velocities up to 217 mm/s in the 1.5T scanner and 38 mm/s in the 0.5T scanner. We measured knee joint kinematics with small intraobserver variation (variance of 0.8° for rotation and 3.6% of patellar width for translation).

Conclusion

Our results suggest that real‐time MRI can be used to measure joint kinematics when 2 mm accuracy is sufficient. They can also be used to prescribe the speed of joint motion necessary to achieve certain measurement accuracy. J. Magn. Reson. Imaging 2008;28:158–166. © 2008 Wiley‐Liss, Inc.
Cartilage imaging at 3.0T with gradient refocused acquisition in the steady‐state (GRASS) and IDEAL fat‐water separation
Authors: Kijowski Richard , Tuite Michael , Passov Leo , Shimakawa Ann , Hu Huanzhou , Reeder Scott B.
Published: June 2008

Purpose

To demonstrate the feasibility of evaluating the articular cartilage of the knee joint at 3.0T using gradient refocused acquisition in the steady‐state (GRASS) and iterative decomposition of water and fat with echo asymmetry and least‐squares estimation (IDEAL) fat‐water separation.

Materials and Methods

Bloch equation simulations and a clinical pilot study (n = 10 knees) were performed to determine the influence of flip angle of the IDEAL‐GRASS sequence on the signal‐to‐noise ratio (SNR) of cartilage and synovial fluid and the contrast‐to‐noise ratio (CNR) between cartilage and synovial fluid at 3.0T. The optimized IDEAL‐GRASS sequence was then performed on 30 symptomatic patients as part of the routine 3.0T knee MRI examination at our institution.

Results

The optimal flip angle was 50° for IDEAL‐GRASS cartilage imaging, which maximized contrast between cartilage and synovial fluid. The IDEAL‐GRASS sequence consistently produced high‐quality fat‐ and water‐separated images of the knee with bright synovial fluid and 0.39 × 0.67 × 1.0 mm resolution in 5 minutes. IDEAL‐GRASS images had high cartilage SNR and high contrast between cartilage and adjacent joint structures. The IDEAL‐GRASS sequence provided excellent visualization of cartilage lesions in all patients.

Conclusion

The IDEAL‐GRASS sequence shows promise for use as a morphologic cartilage imaging sequence at 3.0T. J. Magn. Reson. Imaging 2008;28:167–174. © 2008 Wiley‐Liss, Inc.
3D nongadolinium‐enhanced ECG‐gated MRA of the distal lower extremities: Preliminary clinical experience
Authors: Lim Ruth P. , Hecht Elizabeth M. , Xu Jian , Babb James S. , Oesingmann Niels , Wong Samson , Muhs Bart E. , Gagne Paul , Lee Vivian S.
Published: June 2008

Purpose

To report our initial experience implementing a noncontrast‐enhanced electrocardiograph (ECG) gated fast spin echo magnetic resonance angiography (MRA) technique for assessment of the calf arteries.

Materials and Methods

Noncontrast MRA images of 36 clinical patients examined over a 6‐month period were evaluated by two radiologists for length and degree of stenosis of arterial segments. Diagnostic confidence in the technique was also recorded. The reference standard was a consensus reading by both radiologists using the noncontrast technique combined with two gadolinium‐enhanced techniques: bolus‐chase and time‐resolved imaging.

Results

For stenosis evaluation the noncontrast technique demonstrated accuracy 79.4% (1083/1364), sensitivity 85.4% (437/512), and specificity 75.8% (646/852). The sequence demonstrated high negative predictive value (92.3%, 646/700). The technique had serious artifacts leading to poor diagnostic confidence in 17 patients (47.2%). These included motion (n = 7) and artifacts specific to the sequence, including inaccurate trigger delays (n = 5), linear artifact (n = 7), and vessel blurring (n = 5). When only patients in whom there was satisfactory diagnostic confidence were considered, accuracy, sensitivity, and negative predictive value were 92.2% (661/717), 92.4% (158/171), and 97.5% (503/516), respectively.

Conclusion

Our results indicate that when technically successful, noncontrast‐enhanced MRA using ECG‐gated fast spin echo can provide accurate imaging of the calf and pedal arteries. However, further development and optimization are needed to improve the robustness of the technique. J. Magn. Reson. Imaging 2008;28:181–189. © 2008 Wiley‐Liss, Inc.
Change in knee cartilage T2 in response to mechanical loading
Authors: Nishii Takashi , Kuroda Kagayaki , Matsuoka Yuichiro , Sahara Tomohiro , Yoshikawa Hideki
Published: June 2008

Purpose

To assess the clinical feasibility of magnetic resonance (MR) imaging with a mechanical loading system for evaluation of load‐bearing function in knee joints using cartilage T2 as a surrogate of cartilage matrix changes.

Materials and Methods

Sagittal T2 maps of the medial and lateral femorotibial joints of 22 healthy volunteers were obtained using 3.0T MR imaging. After preloading for 6–9 minutes, MR images under static loading conditions were obtained by applying axial compression force of 50% of body weight during imaging. T2 values of the femoral and tibial cartilage at the weight‐bearing area were compared between unloading and loading conditions.

Results

Under loading conditions, mean cartilage T2 decreased, depending on location of the knee cartilage. For the femoral side a significant decrease in T2 with loading was observed only at the region in direct contact with the opposing tibial cartilage, in the medial femoral cartilage (5.4%, P < 0.0005). For the tibial side a significant decrease in T2 with loading was widely observed in the medial and lateral joint, at regions both covered and not covered by the meniscus (4.3%–7.6%, P < 0.005).

Conclusion

MR imaging with mechanical loading is feasible to detect site‐specific changes in cartilage T2 during static loading. J. Magn. Reson. Imaging 2008;28:175–180. © 2008 Wiley‐Liss, Inc.
Investigation and validation of intersite fMRI studies using the same imaging hardware
Authors: Sutton Bradley P. , Goh Joshua , Hebrank Andrew , Welsh Robert C. , Chee Michael W.L. , Park Denise C.
Published: June 2008

Purpose

To provide a between‐site comparison of functional MRI (fMRI) signal reproducibility in two laboratories equipped with identical imaging hardware and software. Many studies have looked at within‐subject reliability and more recent efforts have begun to calibrate responses across sites, magnetic field strengths, and software. By comparing identical imaging hardware and software, we provide a benchmark for future multisite comparisons.

Materials and Methods

We evaluated system compatibility based on noise and stability properties of phantom scans and contrast estimates from repeated runs of a blocked motor and visual task on the same four subjects at both sites.

Results

Analysis of variance (ANOVA) and region of interest (ROI) analysis confirmed that site did not play a significant role in explaining variance in our large fMRI dataset. Effect size analysis shows that between‐subject differences account for nearly 10 times more variance than site effects.

Conclusion

We show that quantitative comparisons of contrast estimates derived from cognitive experiments can reliably be compared across two sites. This allows us to establish an effective platform for comparing group differences between two sites using fMRI when group effects are potentially confounded with site, as in the study of neurocultural differences between countries or multicenter clinical trials. J. Magn. Reson. Imaging 2008;28:21–28. © 2008 Wiley‐Liss, Inc.
3T MR with diffusion tensor imaging and single‐voxel spectroscopy in giant axonal neuropathy
Authors: Brenner Christiana , Speck‐Martins Carlos Eduardo , Farage Luciano , Barker Peter B.
Published: June 2008

Magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and MR spectroscopy (MRS) data were obtained in a patient with giant axonal neuropathy (GAN) and compared to a control group. Fractional anisotropy (FA) and apparent coefficient diffusion (ADC) data were obtained from specific white matter tracts including the corticospinal tracts (CST), corpus callosum (CC), optic radiations (OR), and middle cerebellar peduncle (MCP). Analysis of the MRS was performed. DTI parameters and MRS results were correlated with the neuropathological findings described for GAN. No significant difference between the FA of the CC of the patient and the control group was found. However, there was a significant difference between the FA of the CST, OR, and MCP of the patient and the control group. The ADC values for all tracts of the patient were significantly increased. N‐acetylaspartate to creatine (NAA/Cr) and N‐acetylaspartate to choline (NAA‐Cho) (choline) metabolite ratios were slightly decreased and choline to creatine (Cho/Cr) and myo‐inositol to creatine (Ins/Cr) metabolite ratios were increased in the parietal gray and white matter of the patient as compared to the control group. Cerebellar involvement was less evident. The DTI and MRS findings suggest myelin and axonal damage. J. Magn. Reson. Imaging 2008;28:236–241. © 2008 Wiley‐Liss, Inc.
Impact of heart rate variability in patients with normal sinus rhythm on image quality in coronary magnetic angiography
Authors: Tangcharoen Tarinee , Jahnke Cosima , Koehler Uwe , Schnackenburg Bernhard , Klein Christoph , Fleck Eckart , Nagel Eike
Published: June 2008

Purpose

To evaluate the influence of heart rate variability on image quality in patients with suspected coronary artery disease during magnetic resonance coronary angiography (MRCA).

Materials and Methods

The coronary images from 70 patients who underwent target‐volume MRA were retrospectively analyzed. Two independent observers evaluated image quality using a score from 0 (nonvisible) to 4 (excellent quality). Images were grouped into good (score > 2) and poor image quality (score 0–2). Five parameters (effective scan duration, navigator efficiency, mean heart rate, acquisition window, and heart rate variability) were evaluated.

Results

In all, 56 of the 70 patients (80%) were scored as good and 14 as poor image quality. Only the navigator efficiency, heart rate variability, and acquisition window showed statistically significant for the prediction of image quality, with navigator efficiency being the strongest predictor. Subgroup analysis showed that patients with navigator efficiency >60% had good image quality independent of the heart rate variability. In patients with navigator efficiency ≤60%, heart rate variability is the only remaining significant parameter (P = 0.03).

Conclusion

Navigator efficiency was the most important predictor of MRCA image quality. Heart rate variability is the most important predictor of image quality in patients with a navigator efficiency ≤60%. J. Magn. Reson. Imaging 2008;28:74–79. © 2008 Wiley‐Liss, Inc.
A simplified method for extracting water‐extractable arabinoxylans from wheat flour
Authors: Ganguli Nishath K , Turner Matthew A
Published: June 2008

BACKGROUND: Water‐extractable arabinoxylan (WEAX) is a minor constituent of wheat grain which influences the properties of wheat dough and its end products while conferring numerous health benefits. Consequently, various applications have been proposed for it in foodstuffs. Fortification of food products with pure WEAX extracts represents a simple means to evaluate its effect in these systems. However, rapid methods to isolate relatively pure WEAX are not available. This study aimed to develop a rapid, technically simple means to extract relatively pure WEAX on a small scale.

RESULTS: A simplified process was developed to extract WEAX from wheat flour. After heating, flour WEAX was extracted with water and starch was eliminated by digestion with amyloglucosidase. Most of the protein was removed by adsorption to bentonite and precipitation with 65% ethanol. The final product generated by the developed method consisted of 93 ± 4% arabinoxylan. The WEAX yield was 0.43 ± 0.02% (0.43 ± 0.02 g WEAX/100 g of starting flour) which is higher than that of other methods that generate WEAX of similar purity.

CONCLUSION: This method provides a technically simple means to perform small‐scale isolation of WEAX that contains no detectable contaminating protein. This attribute renders it a preferred input for studies assessing the impact of WEAX fortification on food product quality. Copyright © 2008 Society of Chemical Industry
Assessment of compositional changes during ripening of transgenic papaya modified for protection against papaya ringspot virus
Authors: Roberts Madeen , Minott Donna A , Tennant Paula F , Jackson Jose C
Published: June 2008

BACKGROUND: Papaya (Carica papaya L.) production is limited by over 20 viruses, the most damaging of which is papaya ringspot virus (PRSV). Owing to a lack of suitable PRSV‐resistant sources in Carica germplasm, transgenic resistance using the coat protein (cp) gene of a local PRSV strain is being developed to manage the disease in Jamaica. For assurance of food safety, the nutritional and antinutritional composition of transgenic papayas during ripening was compared with that of unmodified control samples.

RESULTS: Mature unripe fruits of transgenic and non‐transgenic papayas were repeatedly harvested and stored at room temperature for 1 week periods, during which random samples were assessed. With the exception of one transgenic line, no significant differences (P > 0.05) were observed in selected nutrients and antinutrients between the control and test samples at three stages of maturity, although a few random variations were noted.

CONCLUSION: Transformation with viral cp gene and two marker genes did not produce any major unintended alterations in either the nutritional or the antinutritional composition of transgenic papayas. These findings must be compared with other physicochemical and safety assessments to provide a scientific basis for concluding substantial equivalence with conventional papayas available on the market in Jamaica. Copyright © 2008 Society of Chemical Industry
Effects of double-filtration plasmapheresis combined with interferon plus ribavirin for recurrent hepatitis C after living donor liver transplantation
Authors: Takada Yasutsugu , Ito Takashi , Ueda Yoshihide , Haga Hironori , Egawa Hiroto , Tanaka Koichi , Uemoto Shinji
Published: June 2008

Response rates to interferon and ribavirin treatment for recipients with recurrent hepatitis C virus (HCV) infection are suboptimal, particularly for those with genotype 1b and high viral load. The present study evaluated the effects of combining double-filtration plasmapheresis (DFPP) with pharmacotherapy using interferon plus ribavirin after living donor liver transplantation. DFPP was applied in the first week to mechanically eliminate HCV from the blood in the induction phase. One patient could not tolerate DFPP, and another 2 patients discontinued interferon treatment because of adverse effects. Negative results were obtained for HCV-RNA in week 48 (end-treatment response) in 3 patients, and sustained virological response (SVR) was achieved in 2 patients (20%). These response rates were not improved compared to those of the historical non-DFPP group. Although this preliminary study examined only a small number of patients, no additive effect of DFPP was observed in terms of the SVR rate. Liver Transpl, 2008. © 2008 AASLD.
Nifedipine versus carvedilol in the treatment of de novo arterial hypertension after liver transplantation: Results of a controlled clinical trial
Authors: Galioto Alessandra , Semplicini Andrea , Zanus Giacomo , Fasolato Silvano , Sticca Antonietta , Boccagni Patrizia , Frigo Anna Chiara , Cillo Umberto , Gatta Angelo , Angeli Paolo
Published: June 2008

The aim of this study was to compare nifedipine and carvedilol in the treatment of de novo arterial hypertension after orthotopic liver transplantation (OLT). The study included 50 patients who developed arterial hypertension after OLT. Twenty-five patients received nifedipine (group A), and 25 received carvedilol (group B). Patients were defined as intolerant to nifedipine or carvedilol if severe adverse effects developed. These patients stopped the first drug and were switched to the other one. Patients were defined as full responders to monotherapy if there was normalization of blood pressure, and they were defined as partial responders by the need to add a second antihypertensive drug, ramipril. The 2 groups of patients were similar for baseline conditions. At the end of the study, patients intolerant to monotherapy were 48% of group A and 12.5% of group B (P < 0.01). Full responders were 20% of group A and 33.33% of group B (P < 0.01). Partial responders were 22% of group A and 54.1% of group B (P < 0.01). The addition of ramipril normalized blood pressure in 19% of partial responders to monotherapy (75% in partial responders to nifedipine and 30% in partial responders to carvedilol, P < 0.01). In responders to either monotherapy or combined therapy, there was a significant improvement of renal function. In responders to carvedilol, but not in responders to nifedipine, the daily dose of tacrolimus at 1 year should be reduced to 50% compared to the baseline dose to maintain the blood trough level in the therapeutic range. Liver Transpl 14:1020–1028, 2008. © 2008 AASLD.
Interface hepatitis is associated with a high incidence of late graft fibrosis in a group of tightly monitored pediatric orthotopic liver transplantation patients
Authors: Herzog Denise , Soglio Dorothée Bouron-Dal , Fournet Jean-Christophe , Martin Steven , Marleau Denis , Alvarez Fernando
Published: June 2008

Chronic graft dysfunction, manifesting with elevated liver enzymes and histological features of interface hepatitis (IH), is being increasingly recognized as a long-term problem after liver transplantation. The aim of this study was to characterize our group of post–orthotopic liver transplantation (OLT) patients with respect to clinical, laboratory, and histological signs of IH. A retrospective study of charts and liver biopsy specimens from patients transplanted between 1986 and 1999 was used. Histological features of IH were found in 29/119 patients at a median interval of 23.9 months (95% confidence interval −28.2 to 52.6) after OLT. All patients with IH had risk factors for chronic rejection, such as steroid-resistant rejection, acute rejection later than 3 months post-OLT, female receiver of male graft, or pretransplant cytomegalovirus (CMV)-positive serology with a CMV-negative donor liver. None of the 29 had features favoring a diagnosis of de novo autoimmune hepatitis, but 4 had isolated hypergammaglobulinemia, and 4 had non–organ-specific autoantibodies without hyperimmunoglobulin G. Sixteen of 29 patients also had features of chronic rejection, such as foam cell arteriopathy, loss of bile ducts, or pericentral fibrosis. After abnormal biopsy, all but 1 patient were switched to tacrolimus. During a median follow-up of 12 years, death occurred in 5, retransplantation occurred in 7, and definite cirrhosis occurred in 4. In conclusion, IH was detected in 24.4% of our patients and was associated with a high degree of fibrosis development. Most likely, IH represents a form of chronic rejection directed against periportal hepatocytes. Liver Transpl 14:946–955, 2008. © 2008 AASLD.
Expanded indication criteria of living donor liver transplantation for hepatocellular carcinoma at one large-volume center
Authors: Lee Sung-Gyu , Hwang Shin , Moon Deok-Bog , Ahn Chul-Soo , Kim Ki-Hun , Sung Kyu-Bo , Ko Gi-Young , Park Kwang-Min , Ha Tae-Yong , Song Gi-Won
Published: June 2008

The currently available indication criteria of living donor liver transplantation (LDLT) for patients with hepatocellular carcinoma (HCC) have high prognostic power but insufficient discriminatory power. On the basis of single-center results from 221 HCC patients undergoing LDLT, we modified the indication criteria for LDLT to expand recipient selection without increasing the posttransplant recurrence of HCC. Our expanded criteria, based on explant pathology, were largest tumor diameter ≤ 5 cm, HCC number ≤ 6, and no gross vascular invasion. One hundred eighty-six of the 221 HCC patients (84.2%) met our criteria, 10% and 5.5% more than those that met the Milan and University of California at San Francisco (UCSF) criteria, respectively. The overall 5-year patient survival rates were 76.0% and 44.5% within and beyond the Milan criteria, respectively; 75.9% and 36.4% within and beyond the UCSF criteria, respectively; and 76.3% and 18.9% within and beyond our expanded criteria, respectively. Although these 3 sets of criteria had similar prognostic power, our expanded criteria had the highest discriminatory power. Thus, these expanded criteria for LDLT eligibility of HCC patients broaden the indications for patient selection and can more accurately identify patients who will benefit from LDLT. Liver Transpl 14:935–945, 2008. © 2008 AASLD.