bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhancement and degradation of the R relaxation rate resulting from the encapsulation of magnetic particles with hydrophilic coatings
Authors: de Haan Hendrick W. , Paquet Chantal 
Published: June 2011

AbstractThe effects of including a hydrophilic coating around the particles are studied across a wide range of particle sizes by performing Monte Carlo simulations of protons diffusing through a system of magnetic particles. A physically realistic methodology of implementing the coating by cross boundary jump scaling and transition probabilities at the coating surface is developed. Using this formulation, the coating has three distinct impacts on the relaxation rate: an enhancement at small particle sizes, a degradation at intermediate particle sizes, and no effect at large particles sizes. These varied effects are reconciled with the underlying dephasing mechanisms by using the concept of a full dephasing zone to present a physical picture of the dephasing process with and without the coating for all sizes. The enhancement at small particle sizes is studied systemically to demonstrate the existence of an optimal ratio of diffusion coefficients inside/outside the coating to achieve maximal increase in the relaxation rate. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.
B Phase mapping at 7 T and its application for in vivo electrical conductivity mapping
Authors: van Lier Astrid L.H.M.W. , Brunner David O. , Pruessmann Klaas P. , Klomp Dennis W.J. , Luijten Peter R. , Lagendijk Jan J.W. , van den Berg Cornelis A.T. 
Published: June 2011

AbstractIn this study, a new approach to measure local electrical conductivity in tissue is presented, which is based on the propagating B phase and the homogeneous Helmholtz equation. This new MRI technique might open future opportunities for tumor and lesion characterization based on conductivity differences, while it may also find application in radio frequency safety assessment. Prerequisites for conductivity mapping using only the B phase (instead of the complex B field) are addressed. Furthermore it was found that the B phase can be derived directly from the measurable transceive phase arg(B B) in the head. Validation for a human head excited by a 7 T‐birdcage coil using simulations and measurements showed that it is possible to measure in vivo conductivity patterns in the brain using B phase information only. Conductivity contrast between different brain tissues is clearly observed. The measured mean values for white matter, gray matter and cerebrospinal fluid differed 54%, 26%, and −13% respectively from literature values. The proposed method for B phase measurements is very suited for in vivo applications, as the measurement is short (less than a minute per imaged slice) and exposes the patient to low RF power, contrary to earlier proposed approaches. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Glioma cell density in a rat gene therapy model gauged by water relaxation rate along a fictitious magnetic field
Authors: Liimatainen Timo , Sierra Alejandra , Hanson Timothy , Sorce Dennis J. , Ylä‐Herttuala Seppo , Garwood Michael , Michaeli Shalom , Gröhn Olli 
Published: June 2011

AbstractLongitudinal and transverse rotating‐frame relaxation time constants, T1ρ and T2ρ, have previously been successfully applied to detect gene therapy responses and acute stroke in animal models. Those experiments were performed with continuous‐wave irradiation or with frequency‐modulated pulses operating in an adiabatic regime. The technique called Relaxation Along a Fictitious Field (RAFF) is a recent extension of frequency‐modulated rotating‐frame relaxation methods. In RAFF, spin locking takes place along a fictitious magnetic field, and the decay rate is a function of both T1ρ and T2ρ processes. In this work, the time constant characterizing water relaxation with RAFF (TRAFF) was evaluated for its utility as a marker of response to gene therapy in a rat glioma model. To investigate the sensitivity to early treatment response, we measured several rotating‐frame and free‐precession relaxation time constants and the water apparent diffusion coefficients, and these were compared with histological cell counts in 8 days of treated and control groups of animals. TRAFF was the only parameter exhibiting significant association with cell density in three different tumor regions (border, intermediate, and core tissues). These results indicate that TRAFF may provide a marker to identify tumors responding to treatment. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Selective excitation of two‐dimensional arbitrarily shaped voxels with parallel excitation in spectroscopy
Authors: Snyder Jeff , Haas Martin , Hennig Jürgen , Zaitsev Maxim 
Published: June 2011

AbstractParallel excitation is being studied intensively for applications in MR imaging and in particular for selecting arbitrary shapes as regions of interest. In this work, parallel excitation was applied to arbitrarily shaped voxel selection in spectroscopy and investigated for different excitation k‐space trajectories (radial, rectilinear, and spiral) and acceleration factors. Each trajectory was segmented into multiple excitations to increase the overall bandwidth during target selection. Acceleration by parallel excitation was used to decrease the number of segments. Evaluation of spatial and spectral localization of the target of interest was performed in simulation and phantom experiments, and was compared with the point resolved spectroscopy (PRESS) experiment with standard voxels. The selective excitation experiments demonstrated excellent spatial localization and a broad frequency response, although PRESS was superior in direct comparisons with respect to signal‐to‐noise ratio (SNR) and outer volume suppression. Extensive SNR variation was observed dependent on trajectory (8%–90%), with the preferred radial case producing approximately 40%–60% SNR of the PRESS case. Accelerated trajectories at R = 4 provided comparable artifact signal and target excitation accuracy compared with their nonaccelerated counterparts; however, further acceleration (R = 8) resulted in increased artifact (33% increase at R = 8). Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Non‐contrast‐enhanced vascular magnetic resonance imaging using flow‐dependent preparation with subtraction
Authors: Priest Andrew N. , Graves Martin J. , Lomas David J. 
Published: June 2011

AbstractRecent concerns over contrast agent safety have encouraged new developments in non‐contrast‐enhanced vascular imaging techniques. This work investigates the potential for imaging both arteries and veins with vascular anatomy by nonenhanced static subtraction angiography (VANESSA), a method using controllable flow suppression together with subtraction of bright‐ and dark‐blood images. The lower legs of eight healthy volunteers and three patients were imaged using a modified motion‐sensitized driven equilibrium preparation, with three‐dimensional balanced steady‐state free precession readout. The vascular signal decreased with increasing motion‐suppression gradient amplitude, and was suppressed when the velocity‐encoding parameter was (approximately) less than the measured flow velocity. Selected pairs of images were subtracted to depict vessels with either fast flow (e.g. arteries), slow flow (e.g. veins), or both. Several methodological modifications improved image quality and reduced the background signal from static tissues. Subjectively assessed image quality in volunteers was rated as excellent for 56/64 arterial segments, and good or excellent for 35/64 veins. In conclusion, VANESSA enables rapid non‐contrast‐enhanced imaging of arteries and veins, combining information on both morphology and flow. This study demonstrates good technical performance in volunteers and evaluation in patients with vascular disease is warranted. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Phase‐based regional oxygen metabolism (PROM) using MRI
Authors: Fan Audrey P. , Benner Thomas , Bolar Divya S. , Rosen Bruce R. , Adalsteinsson Elfar 
Published: June 2011

AbstractVenous oxygen saturation (Yv) in cerebral veins and the cerebral metabolic rate of oxygen (CMRO2) are important indicators for brain function and disease. Although MRI has been used for global measurements of these parameters, currently there is no recognized technique to quantify regional Yv and CMRO2 using noninvasive imaging. This article proposes a technique to quantify CMRO2 from independent MRI estimates of Yv and cerebral blood flow. The approach uses standard gradient‐echo and arterial spin labeling acquisitions to make these measurements. Using MR susceptometry on gradient‐echo phase images, Yv was quantified for candidate vein segments in gray matter that approximate a long cylinder parallel to the main magnetic field. Local cerebral blood flow for the identified vessel was determined from a corresponding region in the arterial spin labeling perfusion map. Fick's principle of arteriovenous difference was then used to quantify CMRO2 locally around each vessel. Application of this method in young, healthy subjects provided gray matter averages of 59.6% ± 2.3% for Yv, 51.7 ± 6.4 mL/100 g/min for cerebral blood flow, and 158 ± 18 μmol/100 g/min for CMRO2 (mean ± SD, n = 12), which is consistent with values previously reported by positron emission tomography and MRI. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Rapid B1 mapping using orthogonal, equal‐amplitude radio‐frequency pulses
Authors: Chang Yulin V. 
Published: June 2011

AbstractWe present a new phase‐based method for mapping the amplitude of the radio‐frequency field (B1) of a transmitter coil in three‐dimension. This method exploits the noncommutation relation between rotations about orthogonal axes. Our implementation of this principle in the current work results in a simple relation between the phase of the final magnetization and the flip angle (FA). In this study, we focus on FAs less than 90°. Our method is rapid and easy to implement compared with the existing B1 mapping schemes. The mapping sequence can be simply obtained by adding to a regular three‐dimensional gradient‐echo sequence a magnetization preparation radio‐frequency pulse of the same FA but orthogonal in phase to the excitation radio‐frequency pulse. This method is demonstrated capable of generating reliable maps of the B1 field within 1 min using FAs no larger than 60°. We show that it is robust against T1, small chemical shift, and mild background inhomogeneity. This method may especially be suitable for B1 mapping in situations (e.g., long‐T1 and hyperpolarized‐gas imaging) where magnitude‐based methods are not readily applicable. A noise calculation of the FA map using this method is also presented. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Effect of intercompartmental water exchange on the apparent myelin water fraction in multiexponential T2 measurements of rat spinal cord
Authors: Harkins Kevin D. , Dula Adrienne N. , Does Mark D. 
Published: June 2011

AbstractThe myelin water fraction has been used as a quantitative measure of the amount of myelin present in tissue. However, recent work has suggested that intercompartmental exchange of water between myelin and nonmyelin compartments may cause the myelin water fraction to underestimate the true myelin content of tissue. In this work, multiexponential T2 experiments were performed in vivo within the rat spinal cord, and a wide variation of the myelin water fraction (10–35%) was measured within four rat spinal cord tracts with similar myelin content. A numerical simulation based upon segmented histology images was used to quantitatively account for T2 variations between tracts. The model predicts that a difference in exchange between the four spinal cord tracts, mediated by a difference in the average axon radius and myelin thickness, is sufficient to account for the variation in myelin water fraction measured in vivo. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Beneficial effect of albuterol in congenital myasthenic syndrome with epsilon‐subunit mutations
Authors: Sadeh Menachem , Shen Xin‐Ming , Engel Andrew G. 
Published: June 2011

AbstractMutations in the epsilon subunit of the acetylcholine receptor (AChR) are a common cause of congenital myasthenic syndrome (CMS). Patients are usually treated with acetylcholinesterase inhibitors and 3,4‐diaminopyridine with modest clinical benefit. We report 2 patients with CMS due to mutations in the AChR epsilon subunit. The first patient carries two heterozygous frameshift mutations, ε127ins5 and ε1293insG. The second patient is homozygous for the εC142Y mutation that curtails AChR expression to 22% of wild‐type in HEK cells. Treatment with pyridostigmine and 3,4‐diaminopyridine had a limited beneficial effect in the first patient, and the second patient became wheelchair‐bound during therapy. The additional use of albuterol produced dramatic improvement in strength and in activities of daily living in both patients. The efficacy and safety of albuterol in patients who harbor identified low‐expressor or null mutations in the epsilon or other subunits of AChR merits a well‐designed clinical trial. Muscle Nerve, 2011
Reduction of urgency severity is associated with long‐term therapeutic effect after intravesical onabotulinumtoxina injection for idiopathic detrusor overactivity
Authors: Kuo Hann‐Chorng 
Published: June 2011

AbstractAimsIntravesical onabotulinumtoxinA (BoNT‐A) injection is a promising treatment for refractory detrusor overactivity (DO). This study investigated the long‐term success rate of BoNT‐A injection for patients with idiopathic DO and its association with reduction of urgency severity.MethodsThis study was a retrospective analysis of 174 patients with idiopathic DO who received first‐time 100 U BoNT‐A injections. The patients were collected from several previous clinical trials. The therapeutic effects were classified as significant sensory effects with urgency severity score reductions of ≥2 and/or significant motor effects with cystometric bladder capacity increases of ≥25%. The treatment results based on patients' perceptions of bladder conditions and long‐term success rates were analyzed among the different therapeutic‐effect subgroups.ResultsA successful outcome was reported by 138 (79.3%) patients at 3 months. Seventy‐seven (44.3%) patients had both sensory and motor effects, 5 (2.9%) had sensory effects alone, 83 (47.7%) had motor effects alone, and 9 (5.2%) had no sensory or motor effect. All 82 patients with sensory with/without motor effects reported a successful result. In contrast, only 50 (60.2%) patients with motor effects alone reported success at 3 months. Increased cystometric bladder capacity and postvoid residual and decreased voiding efficiency were noted in patients with motor with/without sensory effects. The therapeutic results lasted significantly longer in patients with sensory with/without motor effects than those with motor effects alone.ConclusionsImprovement of urgency severity is significantly associated with a higher success rate at 3 months and longer therapeutic duration after intravesical BoNT‐A injection for IDO. Neurourol. Urodynam. Neurourol. Urodynam. 30: 1497–1502, 2011. © 2011 Wiley Periodicals, Inc.
Racial differences in self‐reported healthcare seeking and treatment for urinary incontinence in community‐dwelling women from the EPI study
Authors: Berger Mitchell B. , Patel Divya A. , Miller Janis M. , DeLancey John O. , Fenner Dee E. 
Published: June 2011

AbstractAimsObjectives of this study are: (1) to examine the prevalence of healthcare seeking among black and white women with self‐reported urinary incontinence (UI), (2) to investigate barriers to treatment for incontinence, and (3) To investigate commonly used therapeutic modalities for UI.MethodsThis is a planned secondary analysis of responses from 2,812 black and white community‐dwelling women living in southeastern Michigan, aged 35–64 years, who completed a telephone interview concerning UI, healthcare‐seeking behaviors and management strategies. The study population was 571 subjects (278 black, 293 white) who self‐identified as having urinary incontinence.ResultsOf these women with UI, 51% sought healthcare with no statistically significant difference between the two races (53% black, 50.6% white, P = 0.64). In multivariate logistic regression analysis, a higher likelihood of seeking healthcare was associated with increased age, body mass index lower than 30 kg/m2, prior surgery for UI, having regular pelvic exams, having a doctor, and worsening severity of UI. There was no significant association between hypothesized barriers to care seeking and race. Almost 95% of the subjects identified lack of knowledge of available treatments as one barrier. Black and white women were similar in percentage use of medications and some self‐care strategies, for example, pad wearing and bathroom mapping, but black women were significantly more likely to restrict fluid intake than white women and marginally less likely to perform Kegels.ConclusionsBlack and white women seek healthcare for UI at similar, low rates. Improved patient‐doctor relationships and public education may foster healthcare seeking behavior. Neurourol. Urodynam. Neurourol. Urodynam. 30: 1442–1447, 2011. © 2011 Wiley Periodicals, Inc.
Functional characterization of a chronic cyclophosphamide‐induced overactive bladder model in mice
Authors: Boudes Mathieu , Uvin Pieter , Kerselaers Sara , Vennekens Rudi , Voets Thomas , De Ridder Dirk 
Published: June 2011

AbstractAimsTo describe a new mouse model of overactive bladder (OAB) at the histological level, pain, voiding behavior, and urodynamics, while assessing the physiological state of mice.MethodsThis paper compares the pathophysiological features of mice that received intraperitoneal injections of cyclophosphamide (CYP) (40 and 80 mg/kg − body weight) every 2 days for 7 days. Specifically, the heart rate, the body temperature, and the general activity were assessed by telemetry. The abdominal sensitivity was determined with Von Frey filaments. Voiding behavior and detrusor activity were respectively quantified by urine spotting experiments and cystometry. Hematoxylin & Eosin staining was performed to detect inflammation in tissue and NGF concentration in urine was quantified.ResultsAffected mice exhibit clearly an OAB characterized by an increase in the number of voiding events and an urodynamically‐demonstrated detrusor overactivity associated with referred hyperalgesia. The injected mice displayed inflamed bladder, urothelial hyperplasia, and increased NGF concentration in urine in dose dependant manner. However, the physiological features of mice with CYP‐induced cystitis are not changed.ConclusionsWe can show that this model of chronic OAB with pain in mice fits more closely to the clinical signs of patients with OAB than the available animal models (acute and chronic) and will therefore be useful to highlight potential drug targets in genetically modified mice in the future. Neurourol. Urodynam. Neurourol. Urodynam. 30: 1659–1665, 2011. © 2011 Wiley Periodicals, Inc.
Natural hp‐BEM for the electric field integral equation with singular solutions
Authors: Bespalov Alexei , Heuer Norbert 
Published: June 2011

AbstractWe apply the hp ‐version of the boundary element method (BEM) for the numerical solution of the electric field integral equation (EFIE) on a Lipschitz polyhedral surface Γ. The underlying meshes are supposed to be quasi‐uniform triangulations of Γ, and the approximations are based on either Raviart‐Thomas or Brezzi‐Douglas‐Marini families of surface elements. Nonsmoothness of Γ leads to singularities in the solution of the EFIE, severely affecting convergence rates of the BEM. However, the singular behavior of the solution can be explicitly specified using a finite set of functions (vertex‐, edge‐, and vertex‐edge singularities), which are the products of power functions and poly‐logarithmic terms. In this article, we use this fact to perform an a priori error analysis of the hp ‐BEM on quasi‐uniform meshes. We prove precise error estimates in terms of the polynomial degree p, the mesh size h, and the singularity exponents. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2012
Reduced expression of transforming growth factor‐β1 and correlated elevation of interleukin‐17 and interferon‐γ in pediatric patients with chronic primary immune thrombocytopenia (ITP)
Authors: Wang Jiaan‐Der , Chang Te‐Kau , Lin Heng‐Kuei , Huang Fang‐Liang , Wang Chau‐Jong , Lee Huei‐Jane 
Published: June 2011

AbstractBackgroundDysregulated T helper (Th) cells are considered important in the pathophysiology of chronic primary immune thrombocytopenia (ITP). The present study investigated whether levels of Th cytokines in pediatric patients with chronic ITP were different compared with healthy controls.ProceduresFifty‐seven pediatric patients with chronic ITP and 28 healthy controls were enrolled. Patients were divided into three groups based on their platelet counts at the time of the study: (i) active disease <50 × 109/l (n = 23), (ii) stable disease 50–150 × 109/l (n = 23), and (iii) in remission >150 × 109/l (n = 11). Plasma concentration of Th1 [interferon gamma (INF‐γ), interleukin 2 (IL‐2)], Th2 (IL‐4, IL‐10), Th3 [transforming growth factor‐β1 (TGF‐β1)], and Th17 (IL‐17) cytokines were investigated by enzyme‐linked immunosorbent assay.ResultsIFN‐γ was increased in patients with active (P < 0.001) and stable disease (P = 0.026) when compared with controls. The IL‐17 level was significantly higher in all of the 3 patient groups. In addition, there was a positive correlation between IL‐17 and IFN‐γ levels in chronic ITP patients (r = 0.640, P < 0.001). Reduced TGF‐β1 expression was observed in patients with active (P < 0.001) and stable disease (P = 0.001) in comparison with controls. Moreover, TGF‐β1 level in patients was positively correlated with the platelet count (r = 0.355, P = 0.007).ConclusionsElevation of IL‐17 and IFN‐γ may be an important dysregulation of cellular immunity in pediatric patients with chronic ITP. The disease activity is associated with reduced production of TGF‐β1. Pediatr Blood Cancer 2011; 57: 636–640. © 2011 Wiley‐Liss, Inc.
Neutropenia in infants with hemolytic disease of the newborn
Authors: Blanco Esther , Johnston Donna L. 
Published: June 2011

AbstractBackgroundThis study examined the incidence, outcome and risk factors of neutropenia in infants with hemolytic disease of the newborn (HDN).MethodsA retrospective chart review was performed on infants with HDN.ResultsOf 69 evaluable infants, 45% developed neutropenia. Only one infectious complication was recorded. In most instances the neutropenia resolved spontaneously, but in seven infants it persisted for a median of 397 days. Males were at higher risk for developing neutropenia, but severity of HDN, antibody specificity, or therapy were not significant risk factors.ConclusionsNeutropenia is a common feature of HDN, regardless of severity of disease, treatment received, or antibody specificity. Pediatr Blood Cancer 2012; 58: 950–952. © 2011 Wiley Periodicals, Inc.