bluuebunny/crossref_metadata_2025_split huggingface dataset:
ToF‐SWI: Simultaneous time of flight and fully flow compensated susceptibility weighted imaging
Authors: Deistung Andreas , Dittrich Enrico , Sedlacik Jan , Rauscher Alexander , Reichenbach Jürgen R. 
Published: May 2009

AbstractPurposeTo perform systematic investigations on parameter selection of a dual‐echo sequence (ToF‐SWI) for combined 3D time‐of‐flight (ToF) angiography and susceptibility weighted imaging (SWI).Materials and MethodsToF‐SWI was implemented on 1.5 T and 3 T MR scanners with complete 3D first‐order flow compensation of the second echo. The efficiency of flow compensating the SWI echo was studied based on phantom and in vivo examinations. Arterial and venous contrasts were examined in volunteers as a function of flip angle and compared with additionally acquired single‐echo ToF and single‐echo SWI data.ResultsComplete flow compensation is required to reduce arterial contamination in the SWI part caused by signal voids. A ramped flip angle of 20° depicted arteries best while venous contrast was preserved. Comparing ToF‐SWI with single‐echo ToF demonstrated arteries with similar quality and delineated all major arteries equally well. Venous delineation was degraded due to lower SNR associated with the thinner slabs used with ToF‐SWI compared to single‐echo SWI acquisition.ConclusionA dual‐echo sequence (ToF‐SWI) with full flow compensation of the second echo in a single scan is feasible. This sequence allows simultaneous visualization of intrinsically coregistered arteries and veins without spatial mis‐registration of vessels caused by oblique flow and with minimal signal loss in arteries. J. Magn. Reson. Imaging 2009;29:1478–1484. © 2009 Wiley‐Liss, Inc.
Quantification of hepatic steatosis with MRI: The effects of accurate fat spectral modeling
Authors: Reeder Scott B. , Robson Philip M. , Yu Huanzhou , Shimakawa Ann , Hines Catherine DG , McKenzie Charles A. , Brittain Jean H. 
Published: May 2009

AbstractPurposeTo develop a chemical‐shift–based imaging method for fat quantification that accounts for the complex spectrum of fat, and to compare this method with MR spectroscopy (MRS). Quantitative noninvasive biomarkers of hepatic steatosis are urgently needed for the diagnosis and management of nonalcoholic fatty liver disease (NAFLD).Materials and MethodsHepatic steatosis was measured with “fat‐fraction” images in 31 patients using a multiecho chemical‐shift–based water‐fat separation method at 1.5T. Fat‐fraction images were reconstructed using a conventional signal model that considers fat as a single peak at –210 Hz relative to water (“single peak” reconstruction). Fat‐fraction images were also reconstructed from the same source images using two methods that account for the complex spectrum of fat; precalibrated and self‐calibrated “multipeak” reconstruction. Single‐voxel MRS that was coregistered with imaging was performed for comparison.ResultsImaging and MRS demonstrated excellent correlation with single peak reconstruction (r2= 0.91), precalibrated multipeak reconstruction (r2= 0.94), and self‐calibrated multipeak reconstruction (r2= 0.91). However, precalibrated multipeak reconstruction demonstrated the best agreement with MRS, with a slope statistically equivalent to 1 (0.96 ± 0.04;P= 0.4), compared to self‐calibrated multipeak reconstruction (0.83 ± 0.05,P= 0.001) and single‐peak reconstruction (0.67 ± 0.04,P< 0.001).ConclusionAccurate spectral modeling is necessary for accurate quantification of hepatic steatosis with MRI. J. Magn. Reson. Imaging 2009;29:1332–1339. © 2009 Wiley‐Liss, Inc.
Evolution of hyperacute stroke over 6 hours using serial MR perfusion and diffusion maps
Authors: Harris Ashley D. , Kosior Robert K. , Chen Henry S. , Andersen Linda B. , Frayne Richard 
Published: May 2009

AbstractPurposeTo develop an appropriate method to evaluate the time‐course of diffusion and perfusion changes in a clinically relevant animal model of ischemic stroke and to examine lesion progression on MR images. An exploration of acute stroke infarct expansion was performed in this study by using a new methodology for developing time‐to‐infarct maps based on the time at which each voxel becomes infarcted. This enabled definition of homogeneous regions from the heterogeneous stroke infarct.Materials and MethodsTime‐to‐infarct maps were developed based on apparent diffusion coefficient (ADC) changes. These maps were validated and then applied to blood flow and time‐to‐peak maps to examine perfusion changes.ResultsADC stroke infarct showed different evolution patterns depending on the time at which that region of tissue infarcted. Applying the time‐to‐infarct maps to the perfusion maps showed localized perfusion evolution characteristics. In some regions, perfusion was immediately affected and showed little change over the experiment; however, in some regions perfusion changes were more dynamic.ConclusionResults were consistent with the diffusion‐perfusion mismatch hypothesis. In addition, characteristics of collateral recruitment were identified, which has interesting stroke pathophysiology and treatment implications. J. Magn. Reson. Imaging 2009;29:1262–1270. © 2009 Wiley‐Liss, Inc.
Reproducibility of MR perfusion and 1H spectroscopy of bone marrow
Authors: Griffith James F. , Yeung David K.W. , Chow Steven K.K. , Leung Jason Chi Shun , Leung Ping Chung 
Published: May 2009

AbstractPurposeTo determine the reproducibility of proton (1H) magnetic resonance (MR) spectroscopy and dynamic contrast‐enhanced MR imaging in a clinical setting for the assessment of marrow fat fraction and marrow perfusion in longitudinal studies.Materials and MethodsIn all, 36 subjects (17 females, 19 males, mean age 72.9 ± 2.9 years) who underwent MR spectroscopy and/or dynamic contrast‐enhanced perfusion imaging of the proximal femur were asked to return after 1 week for a repeat MR examination.ResultsReproducibility of 1H MR spectroscopy in all bone areas tested was high, ranging from 0.78–0.85, with the highest reproducibility being in the femoral head and lowest in the femoral neck. Reproducibility of paired perfusion measurements ranged from 0.59 (enhancement slope femoral head) to 0.98 (enhancement maximum acetabulum). Overall reproducibility of 1H MR spectroscopy and dynamic contrast‐enhanced imaging tended to be best in areas with the highest inherent fat fraction or perfusion.ConclusionReproducibility of 1H MR spectroscopy or perfusion imaging is sufficiently high to warrant these techniques being applied to the longitudinal study of bone diseases. J. Magn. Reson. Imaging 2009;29:1438–1442. © 2009 Wiley‐Liss, Inc.
Division scheme optimization for the molecular evaluation of the intervertebral disc by gadolinium‐enhanced MRI
Authors: Vaga Stefania , Raimondi Manuela T. , Perona Franco , Fornari Maurizio , Caiani Enrico G. 
Published: May 2009

AbstractPurposeTo evaluate the effects of reducing the number of segments in which the intervertebral disc (IVD) can be subdivided on the accuracy in estimating its sGAG content by computation of the parameter ΔT1 from delayed Gadolinium‐Enhanced MRI of Cartilage (dGEMRIC) protocol.Materials and MethodsTwenty‐three herniectomy patients underwent dGEMRIC acquisitions for IVD. Thirty‐one tissue samples were obtained at herniectomy from the same patients and biochemically analysed for their sGAG content. Eleven different division schemes (DS) were applied by processing dGEMRIC images, and ΔT1 values of the segments related to the surgical sampling locations were computed and correlated to the corresponding biochemical data. For each DS, the linear regression and Pearson's coefficient were computed.ResultsReducing the number of segments from 48 (4 annular rings and 12 angular sectors) to 12 (2 rings and 6 sectors), correlation with sGAG biochemical data did not decline (r > 0.7).ConclusionA 12‐segment DS provided the best compromise between preserving accuracy and reducing the number of segments. J. Magn. Reson. Imaging 2009;29:1443–1449. © 2009 Wiley‐Liss, Inc.
Potential in reducing scan times of HARDI by accurate correction of the cross‐term in a hemispherical encoding scheme
Authors: Cho Kuan‐Hung , Yeh Chun‐Hung , Chao Yi‐Ping , Wang Jiun‐Jie , Chen Jyh‐Horng , Lin Ching‐Po 
Published: May 2009

AbstractPurposeTo reduce the scan time of high angular resolution diffusion imaging (HARDI) by using the hemispherical encoding scheme with the cross‐term correction.Materials and MethodsUnidirectional and 45° crossing phantoms were built to evaluate the accuracy of the fiber orientation estimation when using a hemispherical encoding scheme with and without the cross‐term correction. The q‐ball imaging using the spherical harmonic basis was adopted for estimation of fiber orientation. By recalculating the diffusion gradient strengths, we make the actual b value in all directions equal to the expected b value for the correction of the cross‐term.ResultsThe separation angles measured on the crossing phantom are 42.67° ± 1.50°, 42.75° ± 2.10°, and 42.93° ± 2.78° for cross‐term‐free results, for the results from the hemispherical encoding scheme with and without the cross‐term correction. The angular errors in mapping the unidirectional phantom are 1.87°–2.29° and 4.01°–4.92° for the results using the hemispherical encoding scheme with and without correcting for the cross‐term at different b values.ConclusionUsing the hemispherical encoding scheme with the cross‐term correction can potentially halve the scan time of HARDI and obtain accurate fiber orientation estimation simultaneously. This will be helpful in the clinical application of HARDI. J. Magn. Reson. Imaging 2009;29:1386–1394. © 2009 Wiley‐Liss, Inc.
Lower extremities magnetic resonance angiography with blood pressure cuff compression: Quantitative dynamic analysis
Authors: Koenigkam‐Santos Marcel , Sharma Puneet , Kalb Bobby , Carew John , Oshinski John N. , Martin Diego 
Published: May 2009

AbstractPurposeTo quantitatively evaluate changes induced by the application of a femoral blood‐pressure cuff (BPC) on run‐off magnetic resonance angiography (MRA), which is a method generally previously proposed to reduce venous contamination in the leg.Materials and MethodsThis study was Health Insurance Portability and Accountability Act (HIPAA)‐ and Institutional Review Board (IRB)‐compliant. We used time‐resolved gradient‐echo gadolinium (Gd)‐enhanced MRA to measure BPC effects on arterial, venous, and soft‐tissue enhancement. Seven healthy volunteers (six men) were studied with the BPC applied at the mid‐femoral level unilaterally using a 1.5T MR system after intravenous injection of Gd‐BOPTA. Different statistical tools were used such as the Wilcoxon signed rank test and a cubic smoothing spline fit.ResultsWe found that BPC application induces delayed venous filling (as previously described), but also induces significant decreases in arterial inflow, arterial enhancement, vascular‐soft tissue contrast, and delayed peak enhancement (which have not been previously measured).ConclusionThe potential benefits from using a BPC for run‐off MRA must be balanced against the potential pitfalls, elucidated by our findings. J. Magn. Reson. Imaging 2009;29:1450–1456. © 2009 Wiley‐Liss, Inc.
Inter‐ and intraobserver reliability of five MRI sequences in the evaluation of the final volume of cerebral infarct
Authors: Sibon Igor , Ménégon Patrice , Orgogozo Jean‐Marc , Asselineau Julien , Rouanet François , Renou Pauline , Tourdias Thomas , Pachai Chahin , Chêne Genevieve , Dousset Vincent 
Published: May 2009

AbstractPurposeTo evaluate the reproducibility of fluid attenuated inversion recovery (FLAIR) and four other magnetic resonance imaging (MRI) sequences in the quantitative assessment of final cerebral infarct volume.Materials and MethodsFLAIR, T1‐3D, magnetization transfer ratio (MTR)‐map, diffusion‐weighted trace (DWI)‐trace, and apparent diffusion coefficient (ADC)‐map, were acquired and measured in 33 patients 30–45 days after onset of a first‐ever ischemic stroke. The infarct area was visually detected and manually delineated two times by two readers separately after images and sequences randomization. The reliability was assessed by using an intraclass correlation coefficient (ICC) and its two‐sided 95% confidence interval (95% CI).ResultsDWI‐trace had the best reliability, with an ICC of 0.96 (95% CI = 0.93–0.98). FLAIR had an ICC of 0.86 (95% CI = 0.73–0.93), and a much higher volume. T1‐3D, MTR‐map and ADC‐map had lower reliability or excessive volume values equal to 0 in comparison to DWI‐trace.ConclusionDWI‐trace performed within 30th and 45th day following onset of acute ischemic stroke was the most reliable sequence for final infarct volume quantification. This sequence should be added to FLAIR evaluation to strengthen the statistical results of the pharmacological trials and reduce their variability. J. Magn. Reson. Imaging 2009;29:1280–1284. © 2009 Wiley‐Liss, Inc.
Spiral imaging artifact reduction: A comparison of two k‐trajectory measurement methods
Authors: Lechner Silke M. , Sipilä Pekka T. , Wiesinger Florian , Kerr Adam B. , Vogel Mika W. 
Published: May 2009

AbstractPurposeTo compare an external sensor‐based k‐space calibration technique with a routine precalibration method for quantification of method accuracy and reduction of spiral imaging artifacts to obtain improved image quality.Materials and MethodsRecently, magnetic field monitoring (MFM) has been introduced as a new calibration technique of gradient field‐related imperfections. External sensors are placed near the observed object to measure magnetic field variations during image acquisition. The measured field data are used to determine the actual k‐space trajectory and for image reconstruction to reduce artifacts. In the past, precalibration techniques have been proposed where the k‐space trajectory is measured by means of special calibration sequences directly in the object of interest. In this study, MFM is introduced as an effective correction technique for spiral imaging. On the basis of a comparison, whether MFM is as viable as the chosen reference method presented by Duyn et al (J Magn Reson [1998] 132:150–153) is analyzed in terms of detecting imperfections of spatial encoding gradients in order to correct for these in image reconstruction. As this technique is used as a reference method, it is given the acronym Duyn calibration technique (DCT). MFM and DCT are compared and timing delays, k‐space offsets, eddy current effects, k‐trajectory error propagation, image distortions, and signal‐to‐noise ratio were determined for different spiral sequences in two different phantoms.ResultsBoth techniques effectively detect k‐space offsets and k‐trajectory error propagation and correct for general error sources like timing delays. In object border areas, artifacts such as deformations and blurring were dramatically reduced. Within all tested categories, MFM performed as well as DCT. In terms of k‐trajectory error propagation and image distortion quantification, MFM was more accurate.ConclusionWe introduce MFM as an effective and accurate correction technique for spiral imaging, where a comparison of MFM and DCT has shown that both techniques are accurate correction techniques for spiral imaging. J. Magn. Reson. Imaging 2009;29:1485–1492. © 2009 Wiley‐Liss, Inc.
Relaxation times of skeletal muscle metabolites at 7T
Authors: Wang Ligong , Salibi Nouha , Wu Yan , Schweitzer Mark E. , Regatte Ravinder R. 
Published: May 2009

AbstractPurposeTo demonstrate the feasibility of quantitatively evaluating and measuring T1 and T2 relaxation times of human tibialis anterior (TA) muscles metabolites in vivo at 7T and to compare these results with those of 3T.Materials and MethodsA model lipid phantom (corn oil) and healthy volunteers (n = 4, mean ± SD age 35.6 ± 5.6 years) were scanned on 3T and 7T whole‐body MR scanners. A voxel of 10 × 10 × 10 mm3 was positioned on the lipid phantom and right calf TA muscles using the single‐voxel stimulated echo acquisition mode (STEAM) pulse sequence. All magnetic resonance spectroscopy (MRS) data were processed with Java‐based Magnetic Resonance User Interface (JMRUI) using Hankel Lanczos Singular Value Decomposition (HLSVD) filtering to remove the residual water signal.ResultsT1 shows a steady increase while T2 shows a slight decrease with B0 and the spectra show larger spectral resolution at 7T than at 3T in the lipid phantom. T1 values of all the metabolites are higher, while T2 values are slightly lower at 7T than those of 3T compared to reported results in TA. The maximum percentage of increase in T1 is about ≈488%, the maximum percentage of decrease in T2 is about ≈65%.ConclusionThe preliminary results can potentially be used for calculating relaxation correction factors required for absolute quantitation of skeletal muscle metabolite concentrations and for further protocol and sequence optimization. J. Magn. Reson. Imaging 2009;29:1457–1464. © 2009 Wiley‐Liss, Inc.
Settling properties of venous blood demonstrated in the peripheral vasculature using susceptibility‐weighted imaging (SWI)
Authors: Barnes Samuel , Haacke E. Mark 
Published: May 2009

AbstractPurposeTo evaluate the settling properties of venous blood in the peripheral vasculature during periods of immobility.Materials and MethodsSusceptibility‐weighted imaging (SWI) was performed for nine subjects at two time points: within 10 minutes of entering the magnet and after 40 minutes spent stationary in the magnet. Changes in the phase and in the distribution of phase of the veins were used to draw conclusions about the separation of red blood cells from plasma over time.ResultsSettling was observed to occur in eight of the nine subjects, the only exception being the youngest subject (18 years old). The bottom half of some veins was seen to darken while the top half showed little change often with a clear dividing line between the two. Phase values measured in the bottom layer were consistent with the layer consisting entirely of red blood cells. Settling was seen to increase with time spent stationary and to correlate with the size of veins in the calf.ConclusionOlder subjects tended to have larger veins and consequently more settling of the red blood cells. Our results show that even 40 minutes of rest can easily lead to settling of the blood depending on the position of the leg. J. Magn. Reson. Imaging 2009;29:1465–1470. © 2009 Wiley‐Liss, Inc.
Timing bolus dynamic contrast‐enhanced (DCE) MRI assessment of hepatic perfusion: Initial experience
Authors: Baxter Simon , Wang Zhen J. , Joe Bonnie N. , Qayyum Aliya , Taouli Bachir , Yeh Benjamin M. 
Published: May 2009

AbstractPurposeTo assess whether dynamic contrast‐enhanced (DCE) MRI timing bolus data from routine clinical examinations can be postprocessed to obtain hepatic perfusion parameters for diagnosing cirrhosis.Materials and MethodsWe retrospectively identified 57 patients (22 with cirrhosis and 35 without cirrhosis) who underwent abdominal MRI, which included a low‐dose (2 mL gadodiamide) timing bolus using a volumetric spoiled gradient echo T1‐weighted sequence through the abdomen. Using a dual‐input single‐compartment model, the following perfusion parameters were measured: arterial, portal, and total blood flow; arterial fraction; mean transit time; and distribution volume. Those parameters were compared between patients with and without cirrhosis using t‐tests. Receiver operating characteristic (ROC) curve analysis was used to identify the perfusion parameters that can best predict the presence of cirrhosis.ResultsThe hepatic arterial fraction, arterial flow, and distribution volume in patients with cirrhosis (27.7 ± 8.3%, 44.8 ± 14.1 mL/minute/100 g, and 16.3 ± 4.5%, respectively) were significantly higher than those without cirrhosis (18.7 ± 4.4%, 28.5 ± 11.7 mL/minute/100 g, and 14.0 ± 4.2%, respectively; P < 0.05 for all). ROC analysis showed arterial fraction as the best predictor of cirrhosis, with sensitivity of 73% and specificity of 86%.ConclusionTiming bolus DCE MR images from routine examinations can be postprocessed to yield potentially useful hepatic perfusion parameters. J. Magn. Reson. Imaging 2009;29:1317–1322. © 2009 Wiley‐Liss, Inc.
Assessment of hepatic extraction fraction and input relative blood flow using dynamic hepatocyte‐specific contrast‐enhanced MRI
Authors: Nilsson Henrik , Nordell Anders , Vargas Roberto , Douglas Lena , Jonas Eduard , Blomqvist Lennart 
Published: May 2009

AbstractPurposeTo assess the feasibility to use dynamic hepatocyte‐specific contrast‐enhanced MRI (DHCE‐MRI) as an imaging‐based liver function test, and to compare two methods for deconvolutional analysis (DA) in healthy human subjects.Materials and MethodsT1‐weighted DHCE‐MRI with the hepatocyte‐specific contrast medium Gd‐EOB‐DTPA was performed in 20 healthy volunteers. DA was performed using truncated singular value decomposition (TSVD) and Fourier analysis with an appended tail (FA+Tail). Hepatic extraction fraction (HEF) and input relative blood flow (irBF) were calculated for each liver segment. A computer simulation comparing the standard deviation (SD) of TSVD and FA+tail at different levels of signal‐to‐noise (SNR) ratio was performed. The results obtained were compared using descriptive statistics, the Wilcoxon matched pairs test and the variance ratio test.ResultsMedian HEF was 0.201 and 0.205 using TSVD and FA+tail, respectively (P = 0.086). The corresponding results for irBF was 0.240 and 0.239 (P = 0.51). TSVD yielded a smaller SD, although the difference was not significant (P = 0.068 for HEF and P = 0.84 for irBF). The computer simulation showed that TSVD is more stable than FA+tail at most levels of SNR.ConclusionDHCE‐MRI with Gd‐EOB‐DTPA enables the calculation of HEF and irBF. We regard these parameters as being markers of hepatic parenchymal function. J. Magn. Reson. Imaging 2009;29:1323–1331. © 2009 Wiley‐Liss, Inc.
Effects of extracellular matrix molecules on the growth properties of oligodendrocyte progenitor cells in vitro
Authors: Hu Jianguo , Deng Lingxiao , Wang Xiaofei , Xu Xiao‐Ming 
Published: May 2009

AbstractThe extracellular matrix (ECM) is a component of neural cell niches and regulates multiple functions of diverse cell types. To date, limited information is available concerning its biological effects on the growth properties of oligodendrocyte progenitor cells (OPCs). In the present study, we examined effects of several ECM components, i.e., fibronectin, laminin, and Matrigel, on the survival, proliferation, migration, process extension, and purity of OPCs isolated from embryonic day 15 rat spinal cords. All three ECM components enhanced these biological properties of the OPCs compared with a non‐ECM substrate, poly‐D‐lysine. However, the extents of their effects were somewhat different. Among these ECMs, fibronectin showed the strongest effect on almost all aspects of the growth properties of OPCs, implying that this molecule is a better substrate for the growth of OPCs in vitro. Because of its survival‐ and growth‐promoting effects on OPCs, fibronectin may be considered as a candidate substrate for enhancing OPC‐mediated repair under conditions when exogenous delivery or endogenous stimulation of OPCs is applied. © 2009 Wiley‐Liss, Inc.