bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inflow‐based vascular‐space‐occupancy (iVASO) MRI
Authors: Hua Jun , Qin Qin , Donahue Manus J. , Zhou Jinyuan , Pekar James J. , van Zijl Peter C.M. 
Published: February 2011

AbstractVascular‐space‐occupancy (VASO) MRI, a blood nulling approach for assessing changes in cerebral blood volume (CBV), is hampered by low signal‐to‐noise ratio (SNR) because only 10–20% of tissue signal is recovered when using nonselective inversion for blood nulling. A new approach, called inflow‐VASO (iVASO), is introduced in which only blood flowing into the slice has experienced inversion, thereby keeping tissue and cerebrospinal fluid (CSF) signal in the slice maximal and reducing CSF partial volume effects. SNR increases of 198% ± 12% and 334% ± 9% (mean ± SD, n = 7) with respect to VASO were found at TR values of 5s and 2s, respectively. When using inflow approaches, data interpretation is complicated by the fact that signal changes are affected by vascular transit times. An optimal TR‐range (1.5–2.5s) was derived in which the iVASO response during activation predominantly reflects arterial/arteriolar CBV (CBVa) changes. In this TR‐range, perfusion contributions to the signal change are negligible because arterial label has not yet undergone capillary exchange, and arterial and precapillary blood signals are nulled. For TR = 2s, the iVASO signal change upon visual stimulation corresponded to a CBVa increase of 58% ± 7%, in agreement with arteriolar CBV changes previously reported. The onset of the hemodynamic response for iVASO occurred 1.2 ± 0.5s (n = 7) faster than for conventional VASO. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Echo‐planar imaging with prospective slice‐by‐slice motion correction using active markers
Authors: Ooi Melvyn B. , Krueger Sascha , Muraskin Jordan , Thomas William J. , Brown Truman R. 
Published: February 2011

AbstractHead motion is a fundamental problem in functional magnetic resonance imaging and is often a limiting factor in its clinical implementation. This work presents a rigid‐body motion correction strategy for echo‐planar imaging sequences that uses micro radiofrequency coil “active markers” for real‐time, slice‐by‐slice prospective correction. Before the acquisition of each echo‐planar imaging‐slice, a short tracking pulse‐sequence measures the positions of three active markers integrated into a headband worn by the subject; the rigid‐body transformation that realigns these markers to their initial positions is then fed back to dynamically update the scan‐plane, maintaining it at a fixed orientation relative to the head. Using this method, prospectively‐corrected echo‐planar imaging time series are acquired on volunteers performing in‐plane and through‐plane head motions, with results demonstrating increased image stability over conventional retrospective image‐realignment. The benefit of this improved image stability is assessed in a blood oxygenation level dependent functional magnetic resonance imaging application. Finally, a non‐rigid‐body distortion‐correction algorithm is introduced to reduce the remaining signal variation. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Ischemia‐reperfusion injury in rat skeletal muscle assessed with T2‐weighted and dynamic contrast‐enhanced MRI
Authors: Loerakker S. , Oomens C. W. J. , Manders E. , Schakel T. , Bader D. L. , Baaijens F. P. T. , Nicolay K. , Strijkers G. J. 
Published: February 2011

AbstractPressure ulcers are localized areas of soft tissue breakdown due to mechanical loading. Susceptible individuals are subjected to pressure relief strategies to prevent long loading periods. Therefore, ischemia‐reperfusion injury may play an important role in the etiology of pressure ulcers. To investigate the inter‐relation between postischemic perfusion and changes in skeletal muscle integrity, the hindlimbs of Brown Norway rats were subjected to 4‐h ischemia followed by 2‐h reperfusion. Dynamic contrast‐enhanced MRI was used to examine perfusion, and changes in skeletal muscle integrity were monitored with T2‐weighted MRI. The dynamic contrast‐enhanced MRI data showed a heterogeneous postischemic profile in the hindlimb, consisting of areas with increased contrast enhancement (14–76% of the hindlimb) and regions with no‐reflow (5–77%). For T2, a gradual increase in the complete leg was observed during the 4‐h ischemic period (from 34 to 41 msec). During the reperfusion phase, a heterogeneous distribution of T2 was observed. Areas with increased contrast enhancement were associated with a decrease in T2 (to 38 msec) toward preischemic levels, whereas no‐reflow areas exhibited a further increase in T2 (to 42 msec). These results show that reperfusion after prolonged ischemia may not be complete, thereby continuing the ischemic condition and aggravating tissue damage. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Segmented 2D‐selective RF excitations with weighted averaging and flip angle adaptation for MR spectroscopy of irregularly shaped voxel
Authors: Finsterbusch Jürgen , Busch Martin G. 
Published: February 2011

AbstractA weighted averaging scheme with flip angle adaptation is presented for segmented 2D‐selective RF excitations and applied to single‐line segments of a blipped‐planar trajectory. Segments covering the central k‐space, i.e. those with significant signal contributions, are averaged more often than the (outer) segments with low RF amplitudes and minor signal contributions. For compensation, these outer segments are applied with an increased RF amplitude, i.e. a larger flip angle, such that an unaltered signal contribution is obtained in a reduced number of shots. Numerical simulations and experiments in phantoms and the human brain in vivo demonstrate that the approach considerably increases the signal efficiency, i.e. the signal accumulated per time unit, without introducing profile distortions. Its application to single‐voxel MR spectroscopy of a corpus‐callosum‐shaped region‐of‐interest yielded, due to an optimum coverage of the target volume, higher signal amplitudes than conventional localization based on cross‐sectional RF excitations. Thus, the approach could improve the reliability of single‐voxel MR spectroscopy. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Traveling‐wave RF shimming and parallel MRI
Authors: Brunner David O. , Paška Jan , Froehlich Juerg , Pruessmann Klaas P. 
Published: February 2011

AbstractAt sufficiently high Larmor frequencies, traveling electromagnetic waves along a magnet bore can be used for remote magnetic resonance excitation and detection, effectively using the bore as a waveguide. So far, this approach has relied only on the lowest waveguide modes and thus has not supported multiple‐channel operation for radiofrequency shimming and parallel imaging. In this work, this limitation is addressed by establishing a larger number of propagating modes and tapping their spatial field diversity with multiple waveguide ports. The number of available modes is increased by loading with dielectric inserts; the ports are implemented by stub and loop couplers at the end of a waveguide extension. The resulting traveling‐wave array, operated at 298 MHz in a 7T whole‐body magnet, is shown to enable radiofrequency shimming as well as parallel imaging with commonly used acceleration factors. The last part of the study concerns the amount of dielectric loading that is required. For the given Larmor frequency and bore dimensions, it is found that rather few water‐filled inserts, occupying ∼5% of the bore cross‐section, are sufficient for effective parallel imaging. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Comparison of lung T2* during free‐breathing at 1.5 T and 3.0 T with ultrashort echo time imaging
Authors: Yu Jiangsheng , Xue Yiqun , Song Hee Kwon 
Published: February 2011

AbstractAssessment of lung effective transverse relaxation time (T2*) may play an important role in the detection of structural and functional changes caused by lung diseases such as emphysema and chronic bronchitis. While T2* measurements have been conducted in both animals and humans at 1.5 T, studies on human lung at 3.0 T have not yet been reported. In this work, ultrashort echo time imaging technique was applied for the measurement and comparison of T2* values in normal human lungs at 1.5 T and 3.0 T. A 2D ultrashort echo time pulse sequence was implemented and evaluated in phantom experiments, in which an eraser served as a homogeneous short T2* sample. For the in vivo study, five normal human subjects were imaged at both field strengths and the results compared. The average T2* values measured during free‐breathing were 2.11(±0.27) ms at 1.5 T and 0.74(±0.1) ms at 3.0 T, respectively, resulting in a 3.0 T/1.5 T ratio of 2.9. Furthermore, comparison of the relaxation values at end‐expiration and end‐inspiration, accomplished through self‐gating, showed that during normal breathing, differences in T2* between the two phases may be negligible. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Atlas‐based knee cartilage assessment
Authors: Carballido‐Gamio Julio , Majumdar Sharmila 
Published: February 2011

AbstractMagnetic resonance imaging analysis of knee cartilage properties at corresponding anatomic locations could be a valuable tool in studies of knee osteoarthritis by enabling accurate comparisons at practically any region. A technique of this kind is presented in this study. The proposed technique is based on gray‐level bone matching using affine transformations and free‐form deformations thus eliminating the need of bone segmentations and landmark matching. Sixteen subjects of the osteoarthritis initiative with knee osteoarthritis (10 from baseline; 6 from 24‐month follow‐up) were included in this study. Baseline subjects were used to create a gray‐level atlas of the patella with its corresponding mean cartilage thickness and T2 maps. Follow‐up subjects were used to validate atlas‐based point‐to‐point cartilage comparisons. All registrations were qualitatively evaluated with fused gray‐level images of registered patellas. Quantitative evaluation was performed based on mean values of minimum Euclidean distances between matched bone‐cartilage interfaces. A mean distance of 0.554 mm was obtained between the subjects used to build the atlas, and a mean distance of 0.633 mm was found between the atlas and validation subjects. The technique can be applied to other anatomical regions and with other cartilage measures. Qualitative and quantitative results demonstrate the accuracy of the technique and warrant its application in larger cross‐sectional and longitudinal studies of osteoarthritis. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Diffusion imaging with prospective motion correction and reacquisition
Authors: Benner Thomas , van der Kouwe André J. W. , Sorensen A. Gregory 
Published: February 2011

AbstractA major source of artifacts in diffusion‐weighted imaging is subject motion. Slow bulk subject motion causes misalignment of data when more than one average or diffusion gradient direction is acquired. Fast bulk subject motion can cause signal dropout artifacts in diffusion‐weighted images and results in erroneous derived maps, e.g., fractional anisotropy maps. To address both types of artifacts, a fully automatic method is presented that combines prospective motion correction with a reacquisition scheme. Motion correction is based on the prospective acquisition correction method modified to work with diffusion‐weighted data. The images to reacquire are determined automatically during the acquisition from the imaging data, i.e., no extra reference scan, navigators, or external devices are necessary. The number of reacquired images, i.e., the additional scan duration can be adjusted freely. Diffusion‐weighted prospective acquisition correction corrects slow bulk motion well and reduces misalignment artifacts like image blurring. Mean absolute residual values for translation and rotation were <0.6 mm and 0.5°. Reacquisition of images affected by signal dropout artifacts results in diffusion maps and fiber tracking free of artifacts. The presented method allows the reduction of two types of common motion related artifacts at the cost of slightly increased acquisition time. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Combination of complex‐based and magnitude‐based multiecho water‐fat separation for accurate quantification of fat‐fraction
Authors: Yu Huanzhou , Shimakawa Ann , Hines Catherine D. G. , McKenzie Charles A. , Hamilton Gavin , Sirlin Claude B. , Brittain Jean H. , Reeder Scott B. 
Published: February 2011

AbstractMultipoint water–fat separation techniques rely on different water–fat phase shifts generated at multiple echo times to decompose water and fat. Therefore, these methods require complex source images and allow unambiguous separation of water and fat signals. However, complex‐based water–fat separation methods are sensitive to phase errors in the source images, which may lead to clinically important errors. An alternative approach to quantify fat is through “magnitude‐based” methods that acquire multiecho magnitude images. Magnitude‐based methods are insensitive to phase errors, but cannot estimate fat‐fraction greater than 50%. In this work, we introduce a water–fat separation approach that combines the strengths of both complex and magnitude reconstruction algorithms. A magnitude‐based reconstruction is applied after complex‐based water–fat separation to removes the effect of phase errors. The results from the two reconstructions are then combined. We demonstrate that using this hybrid method, 0–100% fat‐fraction can be estimated with improved accuracy at low fat‐fractions. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Detection of neuronal current MRI in human without BOLD contamination
Authors: Luo Qingfei , Jiang Xia , Gao Jia‐Hong 
Published: February 2011

AbstractControversial results regarding the detectability of neuronal current magnetic resonance imaging (ncMRI) have been reported in different studies on human subjects. In all the previous studies, the ncMRI signal was detected under a continuous and paradigm task‐induced blood oxygen level dependent (BOLD) signal background. The aim of this study is to investigate the possibility of detecting ncMRI signal in human brain in the situation that task‐induced BOLD background is absent or minimum. In this study, by adopting an event‐related visuomotor paradigm with long interstimulus interval (=20 s), the ncMRI signal was detected when the BOLD signal fully returned to its baseline, and the potential BOLD background contamination was avoided effectively. The results showed that the visuomotor stimulation elicited BOLD activation in visual and motor cortices, but no significant ncMRI signal change (in magnitude) was detected in human brain. These experimental findings are consistent with theoretical predications. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Determination of the optimal first‐order gradient moment for flow‐sensitive dephasing magnetization‐prepared 3D noncontrast MR angiography
Authors: Fan Zhaoyang , Zhou Xiangzhi , Bi Xiaoming , Dharmakumar Rohan , Carr James C. , Li Debiao 
Published: February 2011

AbstractFlow‐sensitive dephasing (FSD) magnetization preparation has been developed for black‐blood vessel wall MRI and noncontrast MR angiography. The first‐order gradient moment, m1, is a measure of the flow‐sensitization imparted by an FSD preparative module. Determination of the optimal m1 for each individual is highly desirable for FSD‐prepared MR angiography. This work developed a 2D m1‐scouting method that evaluates a range of m1 values for their effectiveness in blood signal suppression in a single scan. The feasibility of using the 2D method to predict blood signal suppression in 3D FSD‐prepared imaging was validated on a flow phantom and the popliteal arteries of 5 healthy volunteers. Excellent correlation of the blood signal measurements between the 2D scouting and 3D FSD imaging was obtained. Therefore, the optimal m1 determined from the 2D m1‐scouting scan may be directly translated to 3D FSD‐prepared imaging. In vivo studies of additional 10 healthy volunteers and 2 patients have demonstrated the proposed method can help significantly improve the signal performance of FSD MR angiography, indicating its potential to enhance diagnostic confidence. Further systematic studies in patients are warranted to evaluate its clinical value. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Unilateral calf atrophy secondary to a de novo mutation of the caveolin‐3 gene
Authors: Arias Gómez Manuel , Alberte‐Woodwar Miguel , Arias‐Rivas Susana , Dapena Dolores , Pintos Elena , Navarro Carmen 
Published: February 2011

AbstractA 23‐year‐old man was evaluated for atrophy of the left calf. He had a myopathic pattern on electromyography. Light microscopy showed dystrophic changes and reduced immunostaining for dysferlin and caveolin‐3. The subsarcolemmal space was enlarged, and abnormal vesicles were visible with electron microscopy. A genetic study showed a heterozygous A45T mutation at exon 2 of the caveolin‐3 gene. Such a mutation has been reported previously with limb‐girdle muscular dystrophy type 1C and rippling muscle disease phenotypes. Muscle Nerve 44: 126–128, 2011.
A mesh adaptation procedure for periodic domains
Authors: Dobrzynski Cécile , Melchior Maxime , Delannay Laurent , Remacle Jean‐François 
Published: February 2011

AbstractIn this paper, an original technique is developed in order to build adaptive meshes on periodic domains. The new approach has the important property that it is code‐reused. The procedure is used against three different algorithms, namely, MAdLib ( Int. J. Numer. Meth. Engng 2000; in press), mmg (Proc. 17th Int. Meshing Roundtable, 2008) and the couple Yams (Rapport Technique RT‐0252, 2001) /Ghs3d (Proc. 8th Int. Meshing Roundtable, 1999). None of the latter algorithms needs to be adapted before it is applied to periodic domains. Some examples of adaptation are presented based on analytical, isotropic and anisotropic mesh‐size fields. Periodicity in translation and rotation both are considered. Finally, the mesh adaptation strategy is used in order to reduce the computational cost of a prediction of strain heterogeneity throughout a periodic polycrystalline aggregate deforming by dislocation slip. Copyright © 2011 John Wiley & Sons, Ltd.
Explicit finite element artificial boundary scheme for transient scalar waves in two‐dimensional unbounded waveguide
Authors: Zhao Mi , Du Xiuli , Liu Jingbo , Liu Heng 
Published: February 2011

AbstractTo simulate the transient scalar wave propagation in a two‐dimensional unbounded waveguide, an explicit finite element artificial boundary scheme is proposed, which couples the standard dynamic finite element method for complex near field and a high‐order accurate artificial boundary condition (ABC) for simple far field. An exact dynamic‐stiffness ABC that is global in space and time is constructed. A temporal localization method is developed, which consists of the rational function approximation in the frequency domain and the auxiliary variable realization into time domain. This method is applied to the dynamic‐stiffness ABC to result in a high‐order accurate ABC that is local in time but global in space. By discretizing the high‐order accurate ABC along artificial boundary and coupling the result with the standard lumped‐mass finite element equation of near field, a coupled dynamic equation is obtained, which is a symmetric system of purely second‐order ordinary differential equations in time with the diagonal mass and non‐diagonal damping matrices. A new explicit time integration algorithm in structural dynamics is used to solve this equation. Numerical examples are given to demonstrate the effectiveness of the proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.
Linking home care interventions and hospitalization outcomes for frail and non‐frail elderly patients
Authors: Monsen Karen A. , Westra Bonnie L. , Oancea S. Cristina , Yu Fang , Kerr Madeleine J. 
Published: February 2011

AbstractStructured clinical data generated using standardized terminologies such as the Omaha System are available for evaluating healthcare quality and patient outcomes. New intervention management grouping approaches are needed to deal with large, complex clinical intervention data sets. We evaluated 56 intervention groups derived using four data management approaches with a data set of 165,700 interventions from 14 home care agencies to determine which approaches and interventions predicted hospitalizations among frail (n = 386) and non‐frail (n = 1,364) elders. Hospitalization predictors differed for frail and non‐frail elders. Low frequencies in some intervention groups were positively associated with hospitalization outcomes, suggesting that there may be a mismatch between the level of care that is needed and the level of care that is provided. © 2011 Wiley Periodicals, Inc. Res Nurs Health
Trajectories of depressive symptoms from adolescence to young adulthood: Chinese Americans versus non‐hispanic whites
Authors: Chen Angela Chia‐Chen , Haas Steven , Gillmore Mary Rogers , Kopak Albert 
Published: February 2011

AbstractWe examined age, sex, and race/ethnicity differences in trajectories of depressive symptom from adolescence to early adulthood; we also tested whether socioeconomic status and acculturation were associated with the differences. The findings suggest that adolescents over age 15 had a higher level and faster decline in depressive symptoms than their younger counterparts; females had higher level and a faster decline in depressive symptoms than males. Chinese American females had the highest depressive symptoms sustained across 7 years; Chinese American males over age 15 had higher depressive symptoms than their White male counterparts. Neither socioeconomic status nor acculturation was significantly associated with the differences in the trajectories. Our findings suggest a need for greater attention to Chinese American adolescents' psychological well‐being. © 2011 Wiley Periodicals, Inc. Res Nurs Health 34:176–191, 2011
Family caregivers of hospitalized adults in Israel: A point‐prevalence survey and exploration of tasks and motives
Authors: Auslander Gail K. 
Published: February 2011

AbstractThe prevalence of family inpatient caregiving in Israel, its extent, content, and related caregiver and patient variables were examined. Of 1,076 patients surveyed, 744 (69%) had family caregivers, and 513 caregivers were interviewed. Caregivers averaged 8 hours a day at the hospital and most frequently carried out monitoring tasks. Their main motivation was the desire to help the patient. Variables that explained overall caregiving tasks were the desire to help the patient (β = .38), to ensure quality of care (β = .19) and external pressure (β = .19). Variables that explained number of hours spent in caregiving were patient's age (β = −.28) and caregiver motivation related to benefits (β = −.19) and separation concerns (β = .18). Staff should identify caregivers, assess their motivations, and help determine appropriate tasks. © 2011 Wiley Periodicals, Inc. Res Nurs Health 34:204–217, 2011