Search Results
Results 301 - 350 of 939
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Brisman J L - - 2008
BACKGROUND AND PURPOSE: Endovascular coil embolization is used increasingly to treat cerebral aneurysms. The purpose of our study was to quantify the incidence of CT-detectable abnormalities after aneurysm coiling and map the radiographic and clinical progression. MATERIALS AND METHODS: We reviewed the radiographic and clinical sequelae of 30 consecutive patients ...
Shidahara Miho - - 2008
PURPOSE: We evaluated the noise reduction capability of wavelet denoising for estimated binding potential (BP) images (k (3)/k (4)) of the peripheral benzodiazepine receptor using (18)F-FEDAA1106 and nonlinear least-square fitting. METHODS: Wavelet denoising within a three-dimensional discrete dual-tree complex wavelet transform was applied to simulate data and clinical dynamic positron ...
Haywood B - - 2007
Results are presented for a model three-axis gradient coil incorporating active acoustic control which is applied to the switched read gradient during a single-shot rapid echo-planar imaging (EPI) sequence at a field strength of 3.0 T. The total imaging acquisition time was 10.6 ms. Substantial noise reduction is achieved both ...
Hyodo F - - 2008
Time-domain (TD) electron paramagnetic resonance (EPR) imaging at 300MHz for in vivo applications requires resonators with recovery times less than 1 micros after pulsed excitation to reliably capture the rapidly decaying free induction decay (FID). In this study, we tested the suitability of the Litz foil coil resonator (LCR), commonly ...
Yoon Jai-Woong - - 2007
The stationary grid commonly used with a digital x-ray detector causes a moiré interference pattern due to the inadequate sampling of the grid shadows by the detector pixels. There are limitations with the previous methods used to remove the moiré such as imperfect electromagnetic interference shielding and the loss of ...
Smith Holly - - 2007
A Helmholtz resonator consists of a hollow neck attached to an empty chamber. This resonator can be modeled as a spring-mass system in which the air moving inside the neck acts as the mass and the gas inside the chamber acts as the spring. Every Helmholtz resonator has a characteristic ...
Boyes Richard G RG Dementia Research Centre, Institute of Neurology, Box 16, University College London, Queen Square, London, UK. - - 2008
Measures of structural brain change based on longitudinal MR imaging are increasingly important but can be degraded by intensity non-uniformity. This non-uniformity can be more pronounced at higher field strengths, or when using multichannel receiver coils. We assessed the ability of the non-parametric non-uniform intensity normalization (N3) technique to correct ...
Seierstad T - - 2007
During the last two decades, there has been an explosive increase in the number of MR investigations involving genetically manipulated mice and rats. Many of the animal studies are performed in a more or less clinical environment, where whole-body MR scanners are the only option available. The quality and acquisition ...
Rondeau Xavier - - 2007
In ground-based astronomy, the inverse problem of phase retrieval from speckle images is a means to calibrate static aberrations for correction by active optics. It can also be used to sense turbulent wavefronts. However, the number of local minima drastically increases with the turbulence strength, mainly because of phase wrapping ...
Lin Fa-Hsuan - - 2007
Multiple receivers can be utilized to enhance the spatiotemporal resolution of MRI by employing the parallel imaging technique. Previously, we have reported the L-curve Tikhonov regularization technique to mitigate noise amplification resulting from the geometrical correlations between channels in a coil array. Nevertheless, one major disadvantage of regularized image reconstruction ...
Awate Suyash P - - 2007
This paper presents a novel method for Bayesian denoising of magnetic resonance (MR) images that bootstraps itself by inferring the prior, i.e., the uncorrupted-image statistics, from the corrupted input data and the knowledge of the Rician noise model. The proposed method relies on principles from empirical Bayes (EB) estimation. It ...
Linn Jennifer - - 2007
Increasing numbers of small animal models are in use in the field of neuroscience research. Magnetic resonance imaging (MRI) provides an excellent method for non-invasive imaging of the brain. Using three-dimensional (3D) MR sequences allows lesion volumetry, e.g. for the quantification of tumor size. Specialized small-bore animal MRI scanners are ...
Ginefri Jean-Christophe - - 2007
Signal-to-noise ratio improvement is of major importance to achieve microscopic spatial resolution in magnetic resonance experiments. Magnetic resonance imaging of small animals is particularly concerned since it typically requires voxels of less than (100 microm)(3) to observe the small anatomical structures having size reduction by a factor of more than ...
Donmez Fuldem Yildirim - - 2008
PURPOSE: To assess the accuracy of magnetic resonance imaging with pelvic phased-array and endorectal coils prospectively, and evaluate if endorectal coil provides any additional information to high resolution pelvic MR imaging in rectal carcinoma staging. MATERIALS AND METHODS: Preoperative MRI of 25 patients with rectal carcinoma was performed with pelvic ...
Castillo-Rubio Carlos F - - 2007
Spatially variant apodization (SVA) is a nonlinear sidelobe reduction technique that improves sidelobe level and preserves resolution at the same time. This method implements a bidimensional finite impulse response filter with adaptive taps depending on image information. Some papers that have been previously published analyze SVA at the Nyquist rate ...
Sosnovik David E - - 2007
PURPOSE: To evaluate the use of a transmit-receive surface (TRS) coil and a cardiac-tailored intensity-correction algorithm for cardiac MRI in mice at 9.4 Tesla (9.4T). MATERIALS AND METHODS: Fast low-angle shot (FLASH) cines, with and without delays alternating with nutations for tailored excitation (DANTE) tagging, were acquired in 13 mice. ...
Vernickel P - - 2007
Multichannel transmit magnetic resonance imaging (MR) systems have the potential to compensate for signal-intensity variations occurring at higher field strengths due to wave propagation effects in tissue. Methods such as RF shimming and local excitation in combination with parallel transmission can be applied to compensate for these effects. Moreover, parallel ...
Huang Tiffany T Y - - 2007
OBJECTIVES: The aim of this study was to characterise the mineral density (MD) of natural enamel white spot lesions (WSLs) using X-ray micro-tomography calibrated with different density hydroxyapatite phantoms. METHODS: Seven natural WSLs from four extracted non-carious premolar teeth were scanned at a voxel size of 7.6 microm using a ...
Settecase Fabio F Department of Medical Imaging and Institute of Medical Science, University of Toronto, Toronto, Ontario, - - 2007
Current applied to wire coils wound at the tip of an endovascular catheter can be used to remotely steer a catheter under magnetic resonance imaging guidance. In this study, we derive and validate an equation that characterizes the relationship between deflection and a number of physical factors: theta/sin(gamma-theta) = nIABL/EI(A) ...
Thomas P C - - 2007
Hyperion is Saturn's largest known irregularly shaped satellite and the only moon observed to undergo chaotic rotation. Previous work has identified Hyperion's surface as distinct from other small icy objects but left the causes unsettled. Here we report high-resolution images that reveal a unique sponge-like appearance at scales of a ...
Hancu Ileana - - 2007
(13)C imaging and spectroscopy in the presence of injected labeled compounds can vastly extend the capability of MRI to perform metabolic imaging. The details of imaging in the presence of injected compounds, however, pose new technological challenges. Pulse sequences, in general, rely on precise flip-angle (FA) calibration to create high ...
Osorio Joseph A - - 2007
PURPOSE: To implement proton magnetic resonance spectroscopic imaging (1H MRSI) at 3 Tesla (3T) using an eight-channel phased-array head coil in a population of brain-tumor patients. MATERIALS AND METHODS: A total of 49 MRI/MRSI examinations were performed on seven volunteers and 34 patients on a 3T GE Signa EXCITE scanner ...
Katscher Ulrich - - 2007
Parallel MRI started with the introduction of coil arrays in improving radiofrequency (RF) acquisition (what is called parallel imaging) and continued with an analogous development for RF transmission (parallel transmission). Based on differences in the spatial sensitivity distributions of the involved array elements, both techniques try to shorten the respective ...
Purkayastha S - - 2007
OBJECTIVE: Circumferential margin involvement (CMI) is an important prognostic indicator for patients with rectal cancer. This meta-analysis aims at evaluating the diagnostic precision of magnetic resonance imaging (MRI) for the preoperative evaluation of CMI in patients with rectal cancer. METHOD: Quantitative meta-analysis was performed comparing MRI against histology after total ...
Carmichael David W DW Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK. - - 2007
We investigated safety issues and potential experimental confounds when performing functional magnetic resonance imaging (fMRI) investigations in human subjects with fully implanted, active, deep brain stimulation (DBS) systems. Measurements of temperature and induced voltage were performed in an in vitro arrangement simulating bilateral DBS during magnetic resonance imaging (MRI) using ...
Ouhlous Mohamed - - 2007
PURPOSE: To evaluate the ability of a custom-built coil design to provide improved signal-to-noise ratio (SNR) and less signal drop with increasing depth at the carotid artery. MATERIALS AND METHODS: Phased-array surface coils can provide a high SNR to image the carotid vessel wall. However, given the required field-of-view (FOV) ...
Meadowcroft Mark D - - 2007
Direct imaging of a histological slice is challenging. The vast difference in dimension between planar size and the thickness of histology slices would require an RF coil to produce a uniform RF magnetic (B1) field in a 2D plane with minimal thickness. In this work a novel RF coil designed ...
Rosen Yael - - 2007
Most prostate MRI/MRS examinations are performed with an endorectal coil inflated with air, leading to an air-tissue interface that induces magnetic susceptibility gradients within the gland. Inflation of the coil with a barium sulfate suspension is described and compared to inflation with air or liquid perfluorocarbon (PFC). The B(0) field ...
Popovici Irina - - 2007
We present a method of locating edges in JPEG-coded images which operates in frequency space on the DCT coefficients. Applied to the quantized DCT coefficients of a block containing a straight edge, the method yields an equation for the edge in a fraction of the operations needed to dequantize and ...
Gufler Hubert - - 2007
The objective of this article is to evaluate the diagnostic accuracy of high-resolution MRI using a microscopy surface coil to stage basal cell carcinomas of the face. High-resolution MRI using a microscopy surface coil is a promising method to determine the extension of basaliomas of the facial region and to ...
Gupta Rashi - - 2007
The DNA microarray technique allows monitoring the expression levels of thousands of genes simultaneously. A single DNA microarray experiment involves a number of error-prone manual and automated processes, which influence the results and have an impact on the subsequent stages of analysis. Typical problems of arrays are pinning errors while ...
Ségonne Florent - - 2007
In this paper, we focus on the retrospective topology correction of surfaces. We propose a technique to accurately correct the spherical topology of cortical surfaces. Specifically, we construct a mapping from the original surface onto the sphere to detect topological defects as minimal nonhomeomorphic regions. The topology of each defect ...
Avdievich N I - - 2007
Typically 31P in vivo magnetic resonance spectroscopic studies are limited by SNR considerations. Although phased arrays can improve the SNR; to date 31P phased arrays for high-field systems have not been combined with 31P volume transmit coils. Additionally, to provide anatomical reference for the 31P studies, without removal of the ...
Georgouli T - - 2008
The eye is involved in several pathologies where precise identification of the underlying condition is essential for the optimal patient care. This preliminary report presents the potential of high-resolution microscopy coil magnetic resonance imaging (HR-MRI) to undertake this task being actively used in the clinical setting. We used a commercially ...
Parvin Bahram - - 2007
Saliency is an important perceptual cue that occurs at different levels of resolution. Important attributes of saliency are symmetry, continuity, and closure. Detection of these attributes is often hindered by noise, variation in scale, and incomplete information. This paper introduces the iterative voting method, which uses oriented kernels for inferring ...
Bentley Michael D - - 2007
The three-dimensional architecture of nephrons in situ and their interrelationship with other nephrons are difficult to visualize by microscopic methods. The present study uses microcomputed X-ray tomography (micro-CT) to visualize intact nephrons in situ. Rat kidneys were perfusion-fixed with buffered formalin and their vasculature was subsequently perfused with radiopaque silicone. ...
Zama Uyrá - - 2007
The sperm of Microstigmus arlei and Microstigmus nigrophthalmus are twisted in a spiral and consist of two regions: the head, formed by an acrosome and a nucleus, and the flagellum, formed by two asymmetric mitochondrial derivatives, a long centriolar adjunct, an axoneme (9+9+2) and two accessory bodies. The head shows ...
Wharton Iain P - - 2007
PURPOSE: To integrate a high intensity focused ultrasound (HIFU) transducer with an MR receiver coil for endocavitary MR-guided thermal ablation of localized pelvic lesions. MATERIALS AND METHODS: A hollow semicylindrical probe (diameter 3.2 cm) with a rectangular upper surface (7.2 cm x 3.2 cm) was designed to house a HIFU ...
Li Lu-Ping - - 2007
PURPOSE: To extend observations on intra-renal oxygenation with blood oxygen level-dependent (BOLD) MRI in human and rats to mouse kidneys imaged with a human whole-body scanner. MATERIALS AND METHODS: Renal BOLD MRI studies were performed on a 3.0T scanner using a multiple gradient-echo (mGRE) sequence with a custom-designed 2.0-cm surface ...
Ben-Artzi Gil - - 2007
In this paper, we introduce a family of filter kernels--the Gray-Code Kernels (GCK) and demonstrate their use in image analysis. Filtering an image with a sequence of Gray-Code Kernels is highly efficient and requires only two operations per pixel for each filter kernel, independent of the size or dimension of ...
Bydder Mark - - 2007
Sensitivity encoding (SENSE) is a magnetic resonance technique that unifies gradient and receive coil encoding. SENSE reconstructs the image by solving a large, ill-conditioned inverse problem, which generally requires regularization and preconditioning. The present study suggests a simple heuristic for determining the regularization parameter. Also discussed are the use of ...
Demongeot Jacques - - 2007
We present in this paper a series of operators coming from various domains of mathematical analysis (approximation theory, differential geometry, optimization and partial differential equations (PDE's)) and able to give adequate responses to low level image processing tasks like contrasting, segmenting and contouring objects of interest in bio-medical images. These ...
Li Yang - - 2007
Simple feedforward ideas are shown to lead to a nearly tenfold increase in the effective bandwidth of a closed-loop piezoelectric positioning stage used in scanning probe microscopy. If the desired control signal is known in advance, the feedforward filter can be acausal: the information about the future can be used ...
Hiratsuka Yoshiyasu - - 2007
PURPOSE: To evaluate the performance advantages of an 8-element phased array head coil (8 ch coil) over a conventional quadrature-type birdcage head coil (QD coil) with regard to the signal-to-noise ratio (SNR) and image uniformity in 3 Tesla magnetic resonance (MR) imaging. MATERIALS AND METHODS: We scanned a phantom filled ...
Surowka Grzegorz - - 2007
We use the wavelet-based decomposition to generate the multiresolution representation of dermatoscopic images of potentially malignant pigmented lesions. Three different machine learning methods are experimentally applied, namely neural networks, support vector machines, and Attributional Calculus. The obtained results confirm that neighborhood properties of pixels in dermatoscopic images are a sensitive ...
Peters Thomas J - - 2007
Microarray images are becoming increasingly important in bioinformatics, proteomics, and in the development of patient-specific therapies. The compression, processing, and analysis of these images are relatively new topics of research. In this paper, we focus on microarray image compression using singular value decomposition (SVD), a well known information compaction method. ...
dos Santos Rafael A P - - 2007
This paper presents a context adaptive coding method for image sequences in hemodynamics. The proposed method implements motion compensation through of a two-stage context adaptive linear predictor. It is robust to the local intensity changes and the noise that often degrades these image sequences, and provides lossless and near-lossless quality. ...
Eskildsen Simon F - - 2007
In the last decade several methods for extracting the human cerebral cortex from magnetic resonance images have been proposed. Studies comparing these methods have been few. In this study we compare a recent cortical extraction method with FreeSurfer, which has been widespread in the scientific community during recent years. The ...
Solis S E - - 2007
A variant coil of the high frequency cavity resonator coil was experimentally developed according to the theoretical frame proposed by Mansfield in 1990. This coil design is similar to the popular birdcage coil but it has the advantage that it can be easily built following the physical principles of the ...
Ardizzone Edoardo - - 2007
Magnetic Resonance images are often characterized by irregularly displaced luminance fluctuations that are called bias artifact. This disturb is due to a drop in signal intensity caused by the distance between imaged sample and receiver coil. An original approach to bias removal in Magnetic Resonance images is presented, which is ...
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