bluuebunny/crossref_metadata_2025 huggingface dataset:
How do disconnected macropores in sloping soils facilitate preferential flow?
Authors: Nieber John L. , Sidle Roy C.
Published: March 2010

Runoff from hillslopes is generated by processes such as infiltration‐excess and saturation overland flow, subsurface stormflow and subsurface return flow. Preferential flow through macropores can affect any one of these runoff generation processes. Field studies at the Hitachi Ohta Experimental Watershed in Japan have noted that self‐organization processes may manifest the connectivity of such subsurface flow paths, particularly via macropores, from hillslopes to stream channels. It is well established from soil physics principles that the connectivity of macropore networks depends on soil wetness and this has been shown experimentally at Hitachi Ohta where subsurface flow and streamflow respond to thresholds of wetness. Numerical solutions to the three‐dimensional Richards equation are derived for a sloping soil block containing a population of disconnected macropores of various sizes, shapes and orientations. Solutions for the case of steady water flux applied to the surface of the soil block are evaluated to determine the conditions where the disconnected macropores become active in the flow process. Results show that subsurface flow is directed through the preferential flow network in the saturated portion of the soil but bypasses the macropores in the drier regions. The preferential flow network expands as the degree of saturation increases. The expanding network of active macropores leads to less resistance to overall flow in the domain and access to increased volumes of the flow domain. Although the individual macropores are disconnected, it is argued that large localized hydraulic gradients can potentially lead to preferred zones of subsurface erosion. In addition to the importance of these findings related to stormflow generation in catchments, they add support to the concept of self‐organization of subsurface flow systems in soils. Copyright © 2010 John Wiley & Sons, Ltd.
Analysis of contaminant transport towards a partially penetrating extraction well in an anisotropic aquifer
Authors: Chen Jui‐Sheng , Wu Chia‐Lun , Liu Chen‐Wuing
Published: March 2010

Installation of a partially penetrating well (PPW) in which only a portion of the well casing is screened is becoming more common because it is very often the case that only a portion of the vertical thickness of the aquifer is contaminated. In this study, we present a mathematical model describing the contaminant transport towards a PPW. To construct the model, the radial and vertical components of the pore water velocity are first computed using an analytical solution for the steady‐state drawdown distribution near a PPW. Next, the obtained radial and vertical components of the pore water velocity are incorporated into a three‐dimensional axially symmetrical advection–dispersion equation in cylindrical coordinates from which the solute transport equation is derived. The Laplace transformed finite difference technique is then adopted to solve the governing equation. The case that contaminant plume is distributed only over the lowermost 20% vertical thickness of the aquifer is considered for simulation. Breakthrough curves at the extraction well and the total mass removal of the contaminant by pumping are both obtained to illustrate how the aquifer remediation using a PPW is affected by various site‐specific hydrogeological parameters. Results demonstrate that the use of the PPW can effectively remove the contaminant only for the aquifer that has a large hydraulic conductivity anisotropy ratio and a small longitudinal dispersivity. The fully penetrating well performs equally or better than the PPW for an aquifer with large longitudinal dispersivity. Moreover, the temporal evolution of the contaminant plume is depicted to gain further insight into the contaminant transport towards a PPW affected by various hydrogeological parameters. The mathematical model presented herein provides a useful tool for designing an effective and efficient pump‐and‐treat system using a PPW. Copyright © 2010 John Wiley & Sons, Ltd.
Comparative assessment of structural and biological properties of biomimetically coated hydroxyapatite on alumina (α‐Al2O3) and titanium (Ti‐6Al‐4V) alloy substrates
Authors: Kapoor Renu , Sistla Pavana Goury , Kumar Jerald Mahesh , Raj T. Avinash , Srinivas G. , Chakraborty Jui , Sinha Mithlesh K. , Basu Debabrata , Pande Gopal
Published: March 2010

Previous reports have shown the use of hydroxyapatite (HAp) and related calcium phosphate coatings on metal and nonmetal substrates for preparing tissue‐engineering scaffolds, especially for osteogenic differentiation. These studies have revealed that the structural properties of coated substrates are dependent significantly on the method and conditions used for coating and also whether the substrates had been modified prior to the coating. In this article, we have done a comparative evaluation of the structural features of the HAp coatings, prepared by using simulated body fluid (SBF) at 25°C for various time periods, on a nonporous metal substrate titanium–aluminium–vanadium (Ti‐6Al‐4V) alloy and a bioinert ceramic substrate alpha‐alumina (α‐Al2O3), with and without their prior treatment with the globular protein bovine serum albumin (BSA). Our analysis of these substrates by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier‐transform infrared (FTIR) spectrometry showed significant and consistent differences in the quantitative and qualitative properties of the coatings. Interestingly, the bioactivity of these substrates in terms of supporting in vitro cell adhesion and spreading, and in vivo effects of implanted substrates, showed a predictable pattern, thus indicating that some coated substrates prepared under our conditions could be more suitable for biological/biomedical applications. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010
Application of different strain regimes in two‐dimensional and three‐dimensional adipose tissue–derived stem cell cultures induces osteogenesis: Implications for bone tissue engineering
Authors: Diederichs Solvig , Böhm Stefanie , Peterbauer Anja , Kasper Cornelia , Scheper Thomas , van Griensven Martijn
Published: March 2010

Mechanical strain has become an important tool in tissue engineering for progenitor cell differentiation. Furthermore, it is used to enhance the mechanical properties of engineered tissue constructs. Although strain amplitude and frequency are well investigated and optimal values are known; application of various strain schemes regarding duration and repetition are not described in literature. In this study, we therefore applied singular and repetitive cyclic strain (1 Hz, 5%) of 15 min short‐time strain and longer strain durations up to 8 h. Additionally, a gradually increasing strain scheme starting with short‐time strain and consecutive elongated strain periods was applied. The cultivation surface was planar silicone on one hand and a three‐dimensionally structured collagen I mesh on the other hand. Adipose tissue–derived mesenchymal stem cells and an osteogenic model cell line (MG‐63) were exposed to these strain regimes and post‐strain cell viability, osteogenic marker gene expression, and matrix mineralization were investigated. Upregulation of alkaline phosphatase, osteocalcin, osteopontin, and BMP‐2/4 revealed that even short‐time strain can enhance osteogenic differentiation. Elongation and repetition of strain, however, resulted in a decline of the observed short‐time strain effects, which we interpret as positively induced cellular adaptation to the mechanically active surroundings. With regard to cellular adaptation, the gradually increasing strain scheme was especially advantageous. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010
Nanosized TiO2 synthesis by EbCDAB microemulsion
Authors: Jian Z. , Fang J. , Peng F.
Published: March 2010

BACKGROUND: Microemulsion is the easiest and cleanest of the popular methods of synthesizing nanomaterial. This work investigated the possibility of forming a single‐phase microemulsion using ethanediyl‐α,β‐bis (cetyldimethylammonium bromide), termed EbCDAB, in a n‐hexanol/water system, and looked for the best scale of microemulsion to synthesize TiO2 to give the best cleaning of organic pollution.

RESULTS: Results confirm that EbCDAB, n‐hexanol and water form a microemulsion system, and this system is an effective way to synthesize nanoparticles of TiO2. Photo catalysis experiments showed sample E6−3 to be the best catalyst, and it decomposed 82% of Methyl Orange (10 mg L−1) in 60 min under UV‐light irradiation. E6−3 had 1.4 times higher activity than the commercial P25. Analyses using transmission electron microscopy (TEM), X‐ray diffraction (XRD), thermographic differential scanning calorimetry (TG‐DSC) and Fourier transform infrared microscopy (FT‐IR), showed that particles of E6−3 were of size around 11 nm and of anatase phase.

CONCLUSION: The best microemulsion was found to have weight ratio n‐hexanol:EbCDAB:water of 6:3:1. At this ratio, TiO2 nanoparticles were easily produced. Copyright © 2010 Society of Chemical Industry
Optimization of the process parameters for the removal of boron from drinking water by electrocoagulation—a clean technology
Authors: Vasudevan Subramanyan , Sheela Sagayaraj Margrat , Lakshmi Jothinathan , Sozhan Ganapathy
Published: March 2010

BACKGROUND: There are a number of articles related to removal of boron by electrocoagulation using aluminium electrodes, but there are fewer articles describing the use of magnesium as the anode material. The main disadvantage of aluminium electrodes is the residual aluminium present in the treated water due to cathodic dissolution, which can create health problems. In the case of magnesium electrodes, there is no such disadvantage. This paper presents the results of studies on the removal of boron using magnesium and stainless steel as anode and cathode, respectively.

RESULTS: Results show that a maximum removal efficiency of 86.32% was achieved at a current density of 0.2 A dm−2 and pH of 7 using magnesium as the anode and stainless steel as the cathode. The adsorption of boron fitted the Langmuir adsorption isotherm, suggesting monolayer coverage of adsorbed molecules. The adsorption process follows second‐order kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature.

CONCLUSIONS: The magnesium hydroxide generated in the cell remove the boron present in the water and reduced to a permissible level and making it drinkable. The process scale up results was consistent with the results obtained from the laboratory scale, showing the robustness of the process. Copyright © 2010 Society of Chemical Industry
Observer variability in the sonographic evaluation of thyroid nodules
Authors: Park Chang Suk , Kim Sung Hun , Jung So Lyung , Kang Bong Joo , Kim Jee Young , Choi Jae Jung , Sung Mi Suk , Yim Hyeon Woo , Jeong Seung Hee
Published: March 2010

Objective.

Inter‐ and intraobserver variabilities in the description and diagnostic categorization of sonographic (US) features of thyroid nodules were evaluated.

Methods.

The current study was conducted on 72 malignant nodules and 61 benign nodules. The US findings for each thyroid nodule were analyzed twice at a 6‐week interval by five radiologists. The analyses were in accordance with the guidelines proposed bythe Thyroid Study Group of the Korean Society of Neuroradiology and Head and Neck Radiology (TSGKSNRHNR). Inter‐ and intraobserver variabilities were calculated using Cohen's kappa statistics. The sensitivity, specificity, positive‐predictive value, and negative‐predictive value in the assessment of the diagnostic accuracy using these guidelines were calculated.

Result.

The interobserver agreement was fair to substantial for US features and categorization. Of the US features of the thyroid nodules, internal content (solid versus cystic) showed substantial agreement (k= 0.64). There was moderate agreement with regard to shape, echogenicity, calcification, and diagnostic categories (k = 0.42, 0.57, 0.55, and 0.55, respectively). There was fair agreement for margin, echotexture, and capsule invasion (k = 0.34, 0.26, and 0.32, respectively). With regard to intraobserver agreement, there was moderate to substantial agreement for all US features except for echotexture and capsule invasion, which showed fair agreement. In particular, there was moderate to almost perfect agreement for the diagnostic category. The sensitivity, specificity, positive‐predictive value, and negative‐predictive value were 65.3%–81.9%, 60.7%–68.9%, 69.7%–73.8%, and 66.6%–75.5%, respectively.

Conclusion.

There were high degrees of inter‐ and intraobserver agreement using the “Guidelines for diagnostic thyroid ultrasonography,” of the TSGKSNRHNR in the description and categorization of thyroid nodules. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound, 2010
Adenovirus retargeting to surface expressed antigens on oral mucosa
Authors: van Zeeburg Hester J. T. , van Beusechem Victor W. , Huizenga Aafke , Haisma Hidde J. , Korokhov Nick , Gibbs Susan , René Leemans C. , Brakenhoff Ruud H.
Published: March 2010

Background

Head and neck squamous cell carcinomas develop in preneoplastic mucosal fields that can extend over several centimeters in diameter. Most of these fields are microscopically recognized as dysplasias. These fields are often not adequately treated and might cause local relapse. Previous investigations demonstrated that mouthwash therapy with oncolytic adenoviruses appears to be a good option for the treatment of these fields, although, at present, with limited efficacy.

Methods

Immunohistochemistry on normal and preneoplastic mucosa was applied to determine the expression levels of the coxsackie adenoviral receptor (CAR) and a few surface antigens that might allow retargeting: Ly‐6D, CD44v6 and K928. Monoclonal antibodies directed against these surface antigens were used for retargeting of adenoviruses in model experiments with organotypic cultures of mucosal epithelium. A bispecific single chain antibody was constructed against both the adenoviral knob and Ly‐6D.

Results

Immunohistochemical staining revealed that CAR is present only at a low level in the basal layers of the oral mucosa of both normal and dysplastic lesions. By contrast, Ly‐6D, CD44v6 and K928 were abundantly expressed and Ly‐6D even on the most superficial layers. Monoclonal antibodies against Ly‐6D and CD44v6 were shown to enhance infection in an organotypic cell culture by one log. Based on these observations, we constructed a bispecific single chain antibody against Ly‐6D and adenovirus fiber knob, and showed that this engineered molecule allows efficient CAR‐independent infection.

Conclusions

Retargeting of oncolytic adenovirus to other surface molecules might improve the efficacy of virotherapy of preneoplastic fields in the oral mucosa. Copyright © 2010 John Wiley & Sons, Ltd.
Biodistribution and safety assessment of AAV2‐GAD following intrasubthalamic injection in the rat
Authors: Fitzsimons Helen L. , Riban Veronique , Bland Ross J. , Wendelken Jennifer L. , Sapan Christine V. , During Matthew J.
Published: March 2010

Background

The steps necessary to translate promising new biological therapies to the clinic are poorly documented. For gene therapy, there are unique aspects that need to be addressed in biodistribution studies. Notably, the spread of the vector beyond the intended target cells or tissue may result in persistent unwanted biological activity or unpredictable biological events; thus, it is critical to evaluate the risks associated with viral vector‐mediated gene transfer prior to embarking on human clinical trials.

Methods

In the present study, we conducted a comprehensive assessment of vector biodistribution throughout the brain, blood and major organs of rats that had been injected via the subthalamic nucleus with recombinant adeno‐associated virus (AAV) expressing glutamic acid decarboxylase (GAD). In addition, behavioral and histological analyses were also performed.

Results

AAV genomes were not detected in blood or cerebrospinal fluid, and did not disseminate to organs outside of the brain in the majority of animals. In the brain, an average of 97.3% of AAV2‐GAD genomes were restricted to the area of the ipsilateral subthalamic nucleus (STN). There were no discernable effects of AAV2‐GAD on general health, and a behavioral assessment of the animals did not reveal any alteration in general behavior, exploration, locomotion or motor symmetry.

Conclusions

The present study met Food and Drug Administration requirements, in addition to efficacy and toxicity studies in rodents and nonhuman primates, to support and supplement a Phase II clinical trial invloving the gene transfer of AAV2‐GAD to the human STN for the potential therapy of Parkinson's disease. Copyright © 2010 John Wiley & Sons, Ltd.
A qualitative analysis of mock jurors' deliberations of linkage analysis evidence
Authors: Charron Angelina , Woodhams Jessica
Published: March 2010

Evidence about a suspect's behavioural similarity across a series of crimes has been presented in legal proceedings in at least three different countries. Its admission as expert evidence, whilst still rare, is becoming more common thus it is important for us to understand how such evidence is received by jurors and legal professionals. This article reports on a qualitative analysis of mock jurors' deliberations about expert linkage analysis evidence. Three groups of mock jurors (N = 20) were presented with the prosecution's linkage analysis evidence from the USA State v. Fortin I murder trial and expert evidence for the defence constructed for the purposes of the study. Each group was asked to deliberate and reach a verdict. Deliberations were video‐recorded and subject to thematic content analysis. The themes that emerged were varied. Analysis suggested that the mock jurors were cautious of the expert evidence of behavioural similarity. In some cases they were sceptical of the expert. They articulated a preference that expert opinion be supported using statistics. Additional themes included jurors having misconceptions concerning what is typical offender behaviour during rape which suggests there is a need for expert linkage analysis evidence regarding behavioural similarities and the relative frequencies of crime scene behaviours. Copyright © 2010 John Wiley & Sons, Ltd.
MRI‐guided procedures in various regions of the body using a robotic assistance system in a closed‐bore scanner: Preliminary clinical experience and limitations
Authors: Moche Michael , Zajonz Dirk , Kahn Thomas , Busse Harald
Published: March 2010

Purpose:

To present the clinical setup and workflow of a robotic assistance system for image‐guided interventions in a conventional magnetic resonance imaging (MRI) environment and to report our preliminary clinical experience with percutaneous biopsies in various body regions.

Materials and Methods:

The MR‐compatible, servo‐pneumatically driven, robotic device (Innomotion) fits into the 60‐cm bore of a standard MR scanner. The needle placement (n = 25) accuracy was estimated by measuring the 3D deviation between needle tip and prescribed target point in a phantom. Percutaneous biopsies in six patients and different body regions were planned by graphically selecting entry and target points on intraoperatively acquired roadmap MR data.

Results:

For insertion depths between 29 and 95 mm, the average 3D needle deviation was 2.2 ± 0.7 mm (range 0.9–3.8 mm). Patients with a body mass index of up to ≈30 kg/m2 fitted into the bore with the device. Clinical work steps and limitations are reported for the various applications. All biopsies were diagnostic and could be completed without any major complications. Median planning and intervention times were 25 (range 20–36) and 44 (36–68) minutes, respectively.

Conclusion:

Preliminary clinical results in a standard MRI environment suggest that the presented robotic device provides accurate guidance for percutaneous procedures in various body regions. Shorter procedure times may be achievable by optimizing technical and workflow aspects. J. Magn. Reson. Imaging 2010;31:964–974. ©2010 Wiley‐Liss, Inc.
Single breath‐hold assessment of ventricular volumes using 32‐channel coil technology and an extracellular contrast agent
Authors: Parish Victoria , Hussain Tarique , Beerbaum Philip , Greil Gerald , Nagel Eike , Razavi Reza , Schaeffter Tobias , Uribe Sergio
Published: March 2010

Purpose:

To evaluate the feasibility of a single breath‐hold 3D cine balanced steady‐state free precession (b‐SSFP) sequence after gadolinium diethylenetriamine penta‐acetic acid (Gd‐DTPA) injection for volumetric cardiac assessment.

Materials and Methods:

Fifteen adult patients routinely referred for cardiac magnetic resonance imaging (MRI) underwent quantitative ventricular volumetry on a clinical 1.5T MR‐scanner using a 32‐channel cardiac coil. A stack of 2D cine b‐SSFP slices covering the ventricles was used as reference, followed by a single breath‐hold 3D cine balanced SSFP protocol acquired before and after administration of Gd‐DTPA. The acquisition was accelerated using SENSE in both phase encoding directions. Volumetric and contrast‐to‐noise data for each technique were assessed and compared.

Results:

The 3D cine protocol was accomplished within one breath‐hold (mean acquisition time 20 sec; spatial resolution 2.1 × 2.1 × 10 mm; temporal resolution 51 msec). The contrast‐to‐noise ratio between blood and myocardium was 234 determined for the multiple 2D cine data, and could be increased for the 3D acquisition from 136 (3D precontrast) to 203 (3D postcontrast) after injecting Gd‐DTPA. In addition the endocardial definition was significantly improved in postcontrast 3D cine b‐SSFP. There was no significant difference for left and right ventricular volumes between standard 2D and 3D postcontrast cine b‐SSFP. However, Bland–Altman plots showed greater bias and scatter when comparing 2D with 3D cine b‐SSFP without contrast.

Conclusion:

3D cine b‐SSFP imaging of the heart using 32 channel coil technology and spatial undersampling allows reliable volumetric assessment within a single breath‐hold after application of Gd‐DTPA. J. Magn. Reson. Imaging 2010;31:838–844. ©2010 Wiley‐Liss, Inc.
Fast three‐dimensional dual echo dixon technique improves fat suppression in breast MRI
Authors: Le‐Petross Huong , Kundra Vikas , Szklaruk Janio , Wei Wei , Hortobagyi Gabriel N. , Ma Jingfei
Published: March 2010

Purpose:

To compare qualitative and quantitative measures of the contrast‐enhanced dual‐echo Dixon technique with the commonly used standard three‐dimensional (3D) gradient echo (spectrally selective fat suppression) technique (SS‐FS) in breast MRI exams (bMRI).

Materials and Methods:

A total of 19 women, with prescheduled bMRI exam, were recruited to our study between 2006 and 2008. Dixon and standard SS‐SF techniques were used on both breasts of each patient. Image quality was rated in five categories: fat suppression quality, fat suppression uniformity, lesion margin clarity, lesion visibility, and axillary visibility. For quantitative assessment, we calculated the signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) of lesion to breast, SNR efficiency, and CNR efficiency.

Results:

Of 19 patients evaluated, 13 had a primary breast malignancy and 6 had benign lesions or negative exams. Dixon images were rated higher in four of five qualitative categories (P < 0.0001) and required a shorter scan time. Dixon images yielded significantly higher SNR (43.8) and CNR (40.1) values than did 3DGRE images (SNR = 34.8, CNR = 25.3; P < 0.05). SNR efficiency (36.30) and CNR efficiency (33.79) values for Dixon images were also higher than were 3DGRE images (SNR efficiency =25.7, CNR efficiency = 19.1; P < 0.05).

Conclusion:

Dixon images were superior to the standard SS‐SF images in both qualitative and quantitative assessment of 19 bMRI exams. The Dixon technique could replace standard SS‐SF technique in bMRI exam, after our findings have been confirmed in future studies with a larger sample size. J. Magn. Reson. Imaging 2010;31:889–894. ©2010 Wiley‐Liss, Inc.
Computational simulations and experimental studies of 3D phase‐contrast imaging of fluid flow in carotid bifurcation geometries
Authors: Marshall Ian
Published: March 2010

Purpose:

To evaluate the use of computational fluid dynamic (CFD)‐based magnetic resonance imaging (MRI) simulations to predict the image appearance and velocity measurement of fluid flow in human carotid bifurcation geometries, and to compare the results with images from experimental MRI studies.

Materials and Methods:

Simulated particle paths were calculated from available CFD datasets of normal and moderately stenosed carotid bifurcation geometries. An MRI simulator based on the spin isochromat method was used to generate images corresponding to a 3D phase‐contrast sequence with velocity encoding in three orthogonal directions. The resulting images were compared qualitatively with experimental MRI scans of the corresponding physical models.

Results:

The simulations predicted the main features observed in experimental studies, such as the low image intensity in regions of complex flow and the position and bright appearance of the jet in the stenosed bifurcation. Simulated velocity images also agreed well with experimental results. The effects of sequence parameters such as repetition time (TR) and echo time (TE) were readily demonstrated by the simulations.

Conclusion:

CFD‐based MRI simulations can be used to predict the appearance of MRI images of regions of physiological flow, and may be useful in the development of improved pulse sequences for flow measurement. J. Magn. Reson. Imaging 2010;31:928–934. ©2010 Wiley‐Liss, Inc.
Intravoxel partially coherent motion technique: Characterization of the anisotropy of skeletal muscle microvasculature
Authors: Karampinos Dimitrios C. , King Kevin F. , Sutton Bradley P. , Georgiadis John G.
Published: March 2010

Purpose:

To propose a reformulation of the intravoxel incoherent motion (IVIM) technique exploiting the low b‐value diffusion‐weighted imaging regime that can characterize microcirculation of tissues perfused with partially coherent blood flow.

Materials and Methods:

The new methodology, termed intravoxel partially coherent motion (IVPCM) technique, is suitable for probing microcirculation in tissues with ordered microvasculature, such as skeletal muscle. We employ a subvoxel model utilizing a randomly oriented bundle of straight vessels whose orientation statistics are characterized by a Fisher axial distribution with concentration parameter K quantifying the anisotropy of the distribution (K = 0 indicates isotropic capillary orientation). The methodology is first validated with a proof‐of‐principle phantom experiment and is then applied to analyze the microvasculature of human calf muscle at rest.

Results:

The microcirculatory part of the diffusion‐weighted signal at b < 200 s/mm2 is anisotropic. The variation of the diffusion‐weighted signal with b‐value exhibits stronger deviation from the expected monoexponential decay when the diffusion encoding gradient is applied parallel to the mean myofiber direction in the calf muscle of three healthy volunteers. The application of the model to data from the medial gastrocnemius and the soleus of the three volunteers gives results within the expected range for the mean microvascular volume fraction, the mean microflow velocity, and the parameter K.

Conclusion:

The proposed methodology has the capability of characterizing the anisotropy of the capillary network in vivo in a manner analogous to the capability of high b‐value diffusion to characterize the anisotropy of muscle fibers. J. Magn. Reson. Imaging 2010;31:942–953. ©2010 Wiley‐Liss, Inc.
Multiple sclerosis: Hyperintense lesions in the brain on T1‐weighted MR images assessed by diffusion tensor imaging
Authors: Zhou FuQing , Shiroishi Mark , Gong HongHan , Zee Chi‐Shing
Published: March 2010

Purpose:

To evaluate retrospectively quantitative diffusion tensor imaging (DTI) values of hyperintense lesions on nonenhanced T1‐weighted magnetic resonance (MR) images in patients with multiple sclerosis (MS) to elucidate the degree of demyelination or remyelination associated with T1 hyperintense lesions and study their relationship to MR markers of tissue damage (brain atrophy).

Materials and Methods:

Institutional review board approval was obtained; informed consent was waived for this HIPAA‐compliant study, including 76 patients with MS and 20 healthy control subjects without evidence of MS clinically or on imaging. T1 lesions were compared with normal white matter on nonenhanced images and judged to be hyperintense. Quantitative DTI metrics of T1 hyperintense lesions were examined, and the relationship between DTI parameters and brain atrophy were investigated in this study.

Results:

At least one T1 hyperintense lesion was found in 16 patients (total, 28 lesions). Hyperintense lesions on T1‐weighted imaging (T1WI) had lower mean diffusion (MD) than others signal intensity lesions on T1WI but higher MD than normal white matter (F = 3.931; P < 0.001); Fractional anisotropy (FA; F = 3.24; P < 0.001) and volume ratio (VR; F = 1.664; P < 0.001) were higher in hyperintense lesions on T1WI than hypointense/isointense lesions on T1WI, but were lower than normal‐appearing white matter (NAWM) and normal white matter in controls. There was correlation between FA and VR (r = 0.678; P < 0.001) and inverse correlation between FA and MD (r = −0.437; P = 0.02), MD and VR (r = −0.423; P 0.025) for T1 hyperintense lesion. The MD values of T1 hyperintense lesions (r = −0.304; P < 0.001) and the VR values of T1 hyperintense lesions (r = 0.096; P = 0.042) were significantly (negative) correlated with Brain parenchymal fraction (BPF; higher BPF score); the FA values of T1 hyperintense lesions (r = −0.111; P = 0.018), the MD values of T1 hyperintense lesions (r = 0.379; P < 0.001) and the VR values of T1 hyperintense lesions (r = −0.142; P = 0.003) were significantly correlated with third ventricular width (lower width). However, the FA value of T1 hyperintense lesions was not significantly associated with BPF(r = 0.083; P = 0.08).

Conclusion:

The quantitative DTI values of T1 hyperintense MS plaques were between hypo‐/isointense lesions and NAWM or normal white matter, and correlated with BPF and third ventricular width. Our results supports the notion that axonal remyelination may be the reason for T1 hyperintense lesions. J. Magn. Reson. Imaging 2010;31:789–795. ©2010 Wiley‐Liss, Inc.
Assessing vascular response to exercise using a combination of real‐time spiral phase contrast MR and noninvasive blood pressure measurements
Authors: Steeden Jennifer A. , Atkinson David , Taylor Andrew M. , Muthurangu Vivek
Published: March 2010

Purpose:

To measure the hemodynamic response to exercise using real‐time velocity mapping magnetic resonance imaging (MRI), incorporating a high temporal resolution spiral phase contrast (PC) sequence accelerated with sensitivity encoding (SENSE).

Materials and Methods:

Twenty healthy adults underwent MRI at rest and during supine exercise at two different exercise levels. Flow volumes were assessed in the ascending aorta using a spiral SENSE real‐time PC sequence. The sequence was validated at rest against a vendor supplied gated PC sequence, and also at rest and during exercise against left ventricular volumes assessed using a radial k‐t SENSE real‐time sequence. Combining the measured flow volumes with simultaneous oscillometric blood pressure measurements, enabled the noninvasive calculations of systemic vascular resistance (SVR) and arterial compliance (C).

Results:

Measured flow volumes correlated very well between the sequences at rest and during exercise. Cardiac output (CO) and heart rate were found to significantly increase during exercise, while SVR and C were found to decrease significantly.

Conclusion:

Hemodynamic response to exercise can be accurately quantified using a high temporal resolution spiral SENSE real‐time flow imaging. This may allow early detection of hypertension and a greater understanding of the early changes in this condition. J. Magn. Reson. Imaging 2010;31:997–1003. ©2010 Wiley‐Liss, Inc.
Accelerated slice encoding for metal artifact correction
Authors: Hargreaves Brian A. , Chen Weitian , Lu Wenmiao , Alley Marcus T. , Gold Garry E. , Brau Anja C.S. , Pauly John M. , Pauly Kim Butts
Published: March 2010

Purpose:

To demonstrate accelerated imaging with both artifact reduction and different contrast mechanisms near metallic implants.

Materials and Methods:

Slice‐encoding for metal artifact correction (SEMAC) is a modified spin echo sequence that uses view‐angle tilting and slice‐direction phase encoding to correct both in‐plane and through‐plane artifacts. Standard spin echo trains and short‐TI inversion recovery (STIR) allow efficient PD‐weighted imaging with optional fat suppression. A completely linear reconstruction allows incorporation of parallel imaging and partial Fourier imaging. The signal‐to‐noise ratio (SNR) effects of all reconstructions were quantified in one subject. Ten subjects with different metallic implants were scanned using SEMAC protocols, all with scan times below 11 minutes, as well as with standard spin echo methods.

Results:

The SNR using standard acceleration techniques is unaffected by the linear SEMAC reconstruction. In all cases with implants, accelerated SEMAC significantly reduced artifacts compared with standard imaging techniques, with no additional artifacts from acceleration techniques. The use of different contrast mechanisms allowed differentiation of fluid from other structures in several subjects.

Conclusion:

SEMAC imaging can be combined with standard echo‐train imaging, parallel imaging, partial‐Fourier imaging, and inversion recovery techniques to offer flexible image contrast with a dramatic reduction of metal‐induced artifacts in scan times under 11 minutes. J. Magn. Reson. Imaging 2010;31:987–996. ©2010 Wiley‐Liss, Inc.
Artifact‐reduced two‐dimensional cine steady state free precession for myocardial blood‐ oxygen‐level‐dependent imaging
Authors: Zhou Xiangzhi , Tsaftaris Sotirios A. , Liu Ying , Tang Richard , Klein Rachel , Zuehlsdorff Sven , Li Debiao , Dharmakumar Rohan
Published: March 2010

Purpose:

To minimize image artifacts in long TR cardiac phase‐resolved steady state free precession (SSFP) based blood‐oxygen‐level‐dependent (BOLD) imaging.

Materials and Methods:

Nine healthy dogs (four male, five female, 20–25 kg) were studied in a clinical 1.5 Tesla MRI scanner to investigate the effect of temporal resolution, readout bandwidth, and motion compensation on long repetition time (TR) SSFP images. Breath‐held 2D SSFP cine sequences with various temporal resolutions (10–204 ms), bandwidths (239–930 Hz/pixel), with and without first‐order motion compensation were prescribed in the basal, mid‐ventricular, and apical along the short axis. Preliminary myocardial BOLD studies in dogs with controllable coronary stenosis were performed to assess the benefits of artifact‐reduction strategies.

Results:

Shortening the readout time by means of increasing readout bandwidth had no observable reduction in image artifacts. However, increasing the temporal resolution in the presence of first‐order motion compensation led to significant reduction in image artifacts. Preliminary studies demonstrated that BOLD signal changes can be reliably detected throughout the cardiac cycle.

Conclusion:

Artifact‐reduction methods used in this study provide significant improvement in image quality compared with conventional long TR SSFP BOLD MRI. It is envisioned that the methods proposed here may enable reliable detection of myocardial oxygenation changes throughout the cardiac cycle with long TR SSFP‐based myocardial BOLD MRI. J. Magn. Reson. Imaging 2010;31:863–871. ©2010 Wiley‐Liss, Inc.
Predicting pathological response to neoadjuvant chemotherapy in breast cancer with quantitative 1H MR spectroscopy using the external standard method
Authors: Tozaki Mitsuhiro , Sakamoto Masaaki , Oyama Yu , Maruyama Katsuya , Fukuma Eisuke
Published: March 2010

Purpose:

To assess the efficacy of quantitative 1H MR spectroscopy (MRS) using the external standard method to predict the pathological response to neoadjuvant chemotherapy with an anthracycline‐based regimen in breast cancer patients.

Materials and Methods:

Sixteen patients with breast cancer were included. Tumor response to chemotherapy was evaluated after the second cycle using MRI and MRS. Final histopathology following surgery after four cycles of chemotherapy served as reference.

Results:

The average normalized choline (Cho) signal was 1.2 (range, 0.40 to 2.8). There were no significant differences in the baseline tumor size and normalized Cho signals between the pathological responders (n = 8) and nonresponders (n = 8). The reduction rates of the normalized Cho signal were statistically significantly different between the pathological responders and nonresponders (P = 0.004), whereas the reduction rates of the lesion size were not significantly different between the two groups. When 40–50% of the reduction rates of the normalized Cho was chosen as the cutoff value, the positive and negative predictive values of MRS were 89% (8/9) and 100% (7/7), respectively.

Conclusion:

The changes in Cho after the second cycle of chemotherapy as determined by quantitative MRS may be more sensitive than changes in the tumor size to predict the pathological response. J. Magn. Reson. Imaging 2010;31:895–902. ©2010 Wiley‐Liss, Inc.
Sub‐millimeter isotropic MRI for segmentation of subcortical brain regions and brain visualization
Authors: Wu Ying , Ragin Ann B. , Du Hongyan , Sidharthan Shawn , Dunkle Eugene E. , Koktzoglou Ioannis , Edelman Robert R.
Published: March 2010

Purpose:

To evaluate a rapid sub‐millimeter isotropic spoiled gradient‐echo (nonselective SPGR) to facilitate the brain subcortical segmentation and the visualization of brain volume compared with the commonly accepted inversion recovery‐prepared SPGR (SPGR‐IR) technique.

Materials and Methods:

The feasibility of the nonselective SPGR was evaluated for two segmentation algorithms. FAST was used to segment the brain into constituent tissue classes (white matter, gray matter, cerebrospinal fluid) and FreeSurfer was used to segment specific subcortical structures (hippocampus, caudate, putamen, and thalamus). Localized apparent signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) values for nonselective SPGR and the SPGR‐IR were compared for the studied subcortical regions. The three‐dimensional volume rendering was generated to evaluate the nonselective SPGR and the SPGR‐IR for brain visualization.

Results:

In basal ganglia regions, nonselective SPGR allows for consistent segmentation results for both FAST and FreeSurfer. This sequence also better differentiated gray/white matter compared with SPGR‐IR. An approximate two‐fold improvement of image quality in apparent SNR and CNR was indicated for subcortical brain anatomical structures with nonselective SPGR versus SPGR‐IR. The nonselective SPGR improved clarity and yielded a more realistic depiction of the brain surface for visualization compared with SPGR‐IR.

Conclusion:

Compared with SPGR‐IR, nonselective SPGR allows for consistent segmentation results for basal ganglia regions and improved clarity for visualization of the brain. J. Magn. Reson. Imaging 2010;31:980–986. ©2010 Wiley‐Liss, Inc.
High temporal resolution SSFP cine MRI for estimation of left ventricular diastolic parameters
Authors: Krishnamurthy Ramkumar , Pednekar Amol , Cheong Benjamin , Muthupillai Raja
Published: March 2010

Purpose:

To obtain high temporal resolution (HTR) magnetic resonance (MR) steady‐state free‐precession (SSFP) cine cardiac images by using multichannel radiofrequency (RF) hardware and parallel imaging techniques; to study the effect of temporal resolution; and to compare the derived left ventricular (LV) diastolic filling parameters with echocardiographic results.

Materials and Methods:

HTR images were acquired in 13 healthy volunteers using a 1.5 T scanner with 32 RF channels and sensitivity encoding (SENSE) and k‐t broad‐use linear‐acquisition speedup technique (k‐t BLAST) imaging techniques. LV diastolic parameters were calculated and compared to conventional echocardiographic indices such as the isovolumic relaxation time (IVRT) and E/A ratio. The need for HTR was assessed and the MR results were compared with echocardiographic results.

Results:

The HTR (≈6‐ms) images yielded higher peak filling rates, peak ejection rates, and peak atrial filling rates. A progressive decline in filling and ejection rates was observed with worsening temporal resolution. The IVRTs and E/A ratios measured with MR versus echocardiography were in broad agreement. Also, SENSE and k‐t BLAST yielded similar diastolic functional parameters.

Conclusion:

With SENSE or k‐t BLAST and modern hardware, HTR cine images can be obtained. The lower temporal resolutions (30–50 ms) used in clinical practice reduce LV filling rates by ≤30% and may hinder characterization of transient phenomena such as the IVRT. J. Magn. Reson. Imaging 2010;31:872–880. ©2010 Wiley‐Liss, Inc.
Breathheld autocalibrated phase‐contrast imaging
Authors: Lew Calvin , Alley Marcus T. , Spielman Daniel M. , Bammer Roland , Chan Frandics P.
Published: March 2010

Purpose:

To compare generalized autocalibrating partially parallel acquisitions (GRAPPA), modified sensitivity encoding (mSENSE), and SENSE in phase‐contrast magnetic resonance imaging (PC‐MRI) applications.

Materials and Methods:

Aliasing of the torso can occur in PC‐MRI applications. If the data are further undersampled for parallel imaging, SENSE can be problematic in correctly unaliasing signals due to coil sensitivity maps that do not match that of the aliased volume. Here, a method for estimating coil sensitivities in flow applications is described. Normal volunteers (n = 5) were scanned on a 1.5 T MRI scanner and underwent PC‐MRI scans using GRAPPA, mSENSE, SENSE, and conventional PC‐MRI acquisitions. Peak velocity and flow through the aorta and pulmonary artery were evaluated.

Results:

Bland–Altman statistics for flow in the aorta and pulmonary artery acquired with mSENSE and GRAPPA methods (R = 2 and R = 3 cases) have comparable mean differences to flow acquired with conventional PC‐MRI. GRAPPA and mSENSE PC‐MRI have more robust measurements than SENSE when there is aliasing artifact caused by insufficient coil sensitivity maps. For peak velocity, there are no considerable differences among the mSENSE, GRAPPA, and SENSE reconstructions and are comparable to conventional PC‐MRI.

Conclusion:

Flow measurements of images reconstructed with autocalibration techniques have comparable agreement with conventional PC‐MRI and provide robust measurements in the presence of wraparound. J. Magn. Reson. Imaging 2010;31:1004–1014. ©2010 Wiley‐Liss, Inc.
Bone matrix imaged in vivo by water‐ and fat‐suppressed proton projection MRI (WASPI) of animal and human subjects
Authors: Wu Yaotang , Hrovat Mirko I. , Ackerman Jerome L. , Reese Timothy G. , Cao Haihui , Ecklund Kirsten , Glimcher Melvin J.
Published: March 2010

Purpose:

To demonstrate water‐ and fat‐suppressed proton projection MRI (WASPI) in a clinical scanner to visualize the solid bone matrix in animal and human subjects.

Materials and Methods:

Pig bone specimens and polymer pellets were used to optimize the WASPI method in terms of soft‐tissue suppression, image resolution, signal‐to‐noise ratio, and scan time on a 3T MRI scanner. The ankles of healthy 2–3‐month‐old live Yorkshire pigs were scanned with the optimized method. The method was also applied to the wrists of six healthy adult human volunteers to demonstrate the feasibility of the WASPI method in human subjects. A transmit/receive coil built with proton‐free materials was utilized to produce a strong B1field. A fast transmit/receive switch was developed to reduce the long receiver dead time that would otherwise obscure the signals.

Results:

Clear 3D WASPI images of pig ankles and human wrists, showing only the solid bone matrix and other tissues with high solid content (eg, tendons), with a spatial resolution of 2.0 mm in all three dimensions were obtained in as briefly as 12 minutes.

Conclusion:

WASPI of the solid matrix of bone in humans and animals in vivo is feasible. J. Magn. Reson. Imaging 2010;31:954–963. ©2010 Wiley‐Liss, Inc.
Silicon planar detectors adapted to slow neutron detection
Authors: Guardiola C. , Fleta C. , Lozano M. , Pellegrini G.
Published: March 2010

Most neutron detectors use some type of conversion material to convert the incident neutrons into secondary charged particles, which can be detected inside the detector bulk afterwards. In these reactions, charged particles and recoil nuclei are emitted, with energies high enough to be distinguished from the gamma ray background. In this way, semiconductor detectors incorporating a layer of a neutron reactive material on top of the substrate can be used as neutron detectors. Based on their experience in the fabrication of radiation detectors, CNM‐IMB (National Center of Microelectronics in Barcelona, Spain) has started a new research line in solid‐state neutron detectors for imaging or dosimetry. The Geant4 Monte–Carlo simulation package has been used to predict the detection efficiency of planar silicon detectors with a neutron converter layer. At the same time, preliminary tests of silicon pad detectors covered with neutron converters have been carried out in the Autonomous University of Barcelona with a neutron source (241Am‐Be). Copyright © 2010 John Wiley & Sons, Ltd.
Long bone fracture repair in mice harboring GFP reporters for cells within the osteoblastic lineage
Authors: Ushiku Chikara , Adams Douglas J. , Jiang Xi , Wang Liping , Rowe David W.
Published: March 2010

GFP reporter mice previously developed to assess levels of osteoblast differentiation were employed in a tibial long bone fracture model using a histological method that preserves fluorescent signals in non‐decalcified sections of bone. Two reporters, based on Col1A1 (Col3.6GFPcyan) and osteocalcin (OcGFPtpz) promoter fragments, were bred into the same mice to reflect an early and late stage of osteoblast differentiation. Three observations were apparent from this examination. First, the osteoprogenitor cells that arise from the flanking periosteum proliferate and progress to fill the fracture zone. These cells differentiate to osteoblasts, chondrocytes, to from the outer cortical shell. Second, the hypertrophic chondrocytes are dispersed and the cartilage matrix mineralized by the advancing Col3.6+ osteoblasts. The endochondral matrix is removed by the following osteoclasts. Third, a new cortical shell develops over the cartilage core and undergoes a remodeling process of bone formation on the inner surface and resorption on the outer surface. The original fractured cortex undergoes resorption as the outer cortical shell remodels inward to become the new diaphyseal bone. The fluorescent microscopy and GFP reporter mice used in this study provide a powerful tool for appreciating the molecular and cellular processes that control these fundamental steps in fracture repair, and may provide a basis for understanding fracture nonunion. Published by Wiley Periodicals, Inc. J Orthop Res 28:1338–1347, 2010