Search Results
Results 251 - 300 of 957
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Adachi Satoru - - 2009
A compact magnetic resonance imaging (MRI) system for a cold (-5 degrees C) room has been developed to acquire MR images below the freezing point of water. The MRI system consists of a 1.0 T permanent magnet, a higher-order shim coil set, and a gradient coil probe, installed in the ...
Folkesson Jenny - - 2009
Magnetic resonance (MR) imaging-based quantitative trabecular bone structure analysis has gained increasing interest in osteoporotic fracture risk assessment and treatment evaluation related to osteoporosis. In vivo MR images of anatomic regions such as the proximal femur and distal tibia are generally acquired with a surface coil in order to obtain ...
Schlamann Marc - - 2009
Endoscopy for evaluation of hoarseness is an invasive procedure and the result depends, to a large extent, on the patient's cooperation. Successful laryngoscopy can also be hampered by unfavourable anatomic conditions, a severely impaired general condition, or severe coagulopathy. We evaluated the feasibility of doing ultra-fast magnetic resonance imaging (MRI), ...
Eryaman Yiğitcan Y Department of Electrical and Electronics Engineering, Bilkent University, 06800 Ankara, Turkey. - - 2009
Internal MRI coils have important applications in diagnostic and interventional studies. Since they can be placed very close to the region of interest in the body, they are favored over external coils in applications where high-resolution images are required. In this paper it is demonstrated that ultimate intrinsic SNR (UISNR) ...
Aubry Sébastien - - 2009
The purpose of this study was to assess the quality of 3-T magnetic resonance (MR) imaging of the skin, to describe skin anatomy at 3 T and to discuss future prospects of skin MRI. A 7-cm single-element surface receiver coil was developed for our 3-T MRI system. Thin sections were ...
van der Zwaag Wietske - - 2009
In this investigation, high-resolution, 1x1x1-mm(3) functional magnetic resonance imaging (fMRI) at 7 T is performed using a multichannel array head coil and a surface coil approach. Scan geometry was optimized for each coil separately to exploit the strengths of both coils. Acquisitions with the surface coil focused on partial brain ...
Andoh Jamila - - 2009
Transcranial magnetic stimulation (TMS) is currently used for cognitive studies and investigated as a treatment for psychiatric disorders. Because of the cortex variability, the coil positioning stage is difficult and should be improved by using individual neuroimaging data. Sophisticated and expensive neuronavigation systems have been developed to guide the coil ...
Roy Catherine - - 2009
OBJECTIVE: The purpose of this retrospective study was to evaluate the accuracy of MRI using pelvic-phased-array and endocavitary coils in detecting intestinal wall invasion by an endometriotic nodule. MATERIALS AND METHODS: Forty-seven patients (32.1 +/- 4.2 years) who were planned for a surgical cure of deep endometriosis underwent MRI with ...
Gabr Refaat E RE Division of MR Research, Department of Radiology, Johns Hopkins School of Medicine, 600 N Wolfe St., Park 328, Baltimore, MD, - - 2009
As the number of MRI phased array coil elements grows, interactions among cables connecting them to the system receiver become increasingly problematic. Fiber optic or wireless links would reduce electromagnetic interference, but their dynamic range (DR) is generally less than that of coaxial cables. Raw MRI signals, however, have a ...
Lattanzi Riccardo R Division of Magnetic Resonance Research, Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, - - 2009
The promise of increased signal-to-noise ratio and spatial/spectral resolution continues to drive MR technology toward higher magnetic field strengths. SAR management and B1 inhomogeneity correction become critical issues at the high frequencies associated with high field MR. In recent years, multiple coil excitation techniques have been recognized as potentially powerful ...
Kocaturk Ozgur - - 2009
BACKGROUND: Catheter visualization and tracking remains a challenge in interventional MR.Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency ...
Duan Yunsuo - - 2009
PURPOSE: To optimize the homogeneity and efficiency of the B(1) magnetic field of a four-ring birdcage head coil that is double-tuned at the Larmor frequencies of both (31)P and (1)H and optimized to acquire magnetic resonance spectroscopy (MRS) data at 3T for the study of infants. MATERIALS AND METHODS: We ...
Morita Yoshinori - - 2009
BACKGROUND: The purpose of this study was to visualize the gastric wall layers and to depict the vascular architecture in vitro by using resected porcine stomachs studied with high-spatial resolution magnetic resonance (MR) imaging. METHODS: Normal dissected porcine stomach samples (n = 4) were examined with a 3 Tesla MR ...
Noor Furqan F Bioelectronics Research Cluster, Department of Electrical & Electronic Engineering, National University of Ireland, Galway, Ireland. - - 2009
The design of an inductive power system is investigated in order to determine the relative benefits provided by the inclusion of a magnetic core in the receiver coil. Both transmitter and receiver coils are chosen to have dimensions similar to those used in many biomedical devices. It is found that ...
Katscher Ulrich U Philips Research Europe-Hamburg, Sector Medical Imaging Systems, 22335 Hamburg, Germany. - - 2009
The electrical conductivity of human tissue could be used as an additional diagnostic parameter or might be helpful for the prediction of the local SAR during MR measurements. In this study, the approach "Electric Properties Tomography" (EPT) is applied, which derives the patient's electric conductivity using a standard MR system. ...
Ha Yong H YH Department of Biomedical Engineering, Kyung Hee University, Yongin, Kyungki, 446-701, Korea. - - 2009
We introduce a magnetic navigation of a small magnet using four stationary coils. We used a Maxwell gradient coil to get magnetic propulsion force and three Helmholtz coils to control the moving direction of the magnet in the magnetic navigation. Using a three-channel coil driver with output capacity of 320A, ...
Bashir Adil A Mallinckrodt Institute of Radiology, St. Louis, Missouri 63110, - - 2009
MRI with hyperpolarized gases, (3)He, (129)Xe, (13)C, and others, has the potential to become an important diagnostic technique for clinical imaging. Due to the nonreversible loss of magnetization in hyperpolarized gas imaging, the choice of the flip angle is a major factor that influences the signal intensity, and hence, the ...
Sundareswaran Kartik S KS Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, - - 2009
To develop and validate a multidimensional segmentation and filtering methodology for accurate blood flow velocity field reconstruction from phase-contrast magnetic resonance imaging (PC MRI). The proposed technique consists of two steps: (1) the boundary of the vessel is automatically segmented using the active contour approach; and (2) the noise embedded ...
Naehle Claas P - - 2008
PURPOSE: To evaluate the safety and feasibility of 3-T magnetic resonance (MR) imaging of the brain in patients with implanted cardiac pacemakers (PMs) by using a transmit-receive head coil. MATERIALS AND METHODS: The study protocol was approved by the institutional review board. Signed informed consent was obtained from all subjects. ...
Lee In Sook - - 2008
OBJECTIVE: The purpose of this study was to evaluate the usefulness of MRI performed with a microscopy coil in the preoperative evaluation of small soft-tissue masses of the hand and foot. MATERIALS AND METHODS: Sixteen patients with clinically suspected soft-tissue masses of the hand or foot underwent MRI with both ...
Wang Zhangwei Z Center for NMR Research, Penn State College of Medicine, Hershey, Pennsylvania 17033, - - 2008
To examine the thermal effects of the physiological response to heating during exposure to radiofrequency (RF) electromagnetic fields in magnetic resonance imaging (MRI) with a head-specific volume coil. Numerical methods were used to calculate the temperature elevation in MRI of the human head within volume coils from 64-400 MHz at ...
Poirier-Quinot Marie - - 2008
The performance of a 12-mm high-temperature superconducting (HTS) surface coil for in vivo microimaging of mice in a standard 1.5T clinical whole-body scanner was investigated. Systematic evaluation of MR image quality was conducted on saline phantoms with various conductivities to derive the sensitivity improvement brought by the HTS coil compared ...
Lo Yat Hei - - 2008
We present novel designs for aspheric lenses used in terahertz (THz) imaging. As different surfaces result in different beam shaping properties and in different losses from reflection and absorption, the resultant imaging resolution (i.e. the focal spot size) depends critically on the design approach. We evaluate the different lens designs ...
Kang Qi - - 2008
A low-impedance capacitively coupled contactless conductivity detector (LIC (4)D) for microchip capillary electrophoresis was reported. The LIC (4)D was the series combination of a piezoelectric quartz crystal (PQC) resonator with a capacitively coupled contactless conductivity detector (C (4)D) outside on the microchip lid. The electrode impedance in the LIC (4)D ...
Yang Jingyu - - 2008
In this paper, we explore the application of 2-D dual-tree discrete wavelet transform (DDWT), which is a directional and redundant transform, for image coding. Three methods for sparsifying DDWT coefficients, i.e., matching pursuit, basis pursuit, and noise shaping, are compared. We found that noise shaping achieves the best nonlinear approximation ...
Pandian Daniel S J - - 2008
PURPOSE: To create a robust means to remove noise pixels using complex data. MATERIALS AND METHODS: A receiver operating characteristic (ROC) curve was used to determine the appropriate choice of magnitude and phase thresholds as well as connectivity values to determine what pixels represent noise in the image. To fine-tune ...
Guarneri F - - 2008
Digital image compression (reduction of the amount of numeric data needed to represent a picture) is widely used in electronic storage and transmission devices. Few studies have compared the suitability of the different compression algorithms for dermatologic images. We aimed at comparing the performance of four popular compression formats, Tagged ...
Tanitame Keizo - - 2008
The purpose of the study was to determine the accuracy of half-Fourier single-shot rapid acquisition with relaxation enhancement high-spatial-resolution magnetic resonance (MR) imaging performed with a microscopy coil in the diagnosis of narrow anterior chamber angle in patients with glaucoma. Slit-lamp biomicroscopy served as the reference standard. The institutional review ...
Han B H - - 2008
Navigating an untethered micro device in a living subject is of great interest for both diagnostic and therapeutic applications. Magnetic propulsion of an untethered device carrying a magnetic core in it is one of the promising methods to navigate the device. MRI gradients coils are thought to be suitable for ...
Kang Chang-Ki - - 2008
The purpose of this study was to evaluate the feasibility of MR angiography (MRA) at 7.0 Tesla (T) using optimized birdcage (BC) coils with simple end cap configurations. Shielded 16-rung high-pass BC coils were built with identical geometry and compared with different sizes and locations of end caps. To determine ...
Zhang Chunguang - - 2008
The development of the large angular aperture noncollinear acousto-optic tunable filter (AOTF) is based on the parallel tangents momentum-matching condition. In this letter, we have introduced a special double-filtering method that leads to an enhancement of the spectral resolution. And the birefringence together with the rotatory property of the interaction ...
Lesecq Marie - - 2008
We report on the characterization of an InP/InGaAsP-material-based microdisk resonator optical filter. The originality here is constituted by the use of a localized control electrode that is used for the tuning of the resonance wavelength of the filter via the injection of a driving current. Tuning of the resonance wavelength ...
Graves Martin J - - 2008
PURPOSE: To investigate the accuracy of low signal-to-noise ratio (SNR) T(2) and T(2)* measurements using array coils and optimal B(1) image reconstruction (OBR) compared to the standard root sum of squares (RSS) reconstruction. MATERIALS AND METHODS: Calibrated gels were used for the in vitro study of T(2). T(2) and T(2)* ...
Gulani Vikas - - 2008
To show that cystic renal lesions that would otherwise meet criteria for simple cysts can demonstrate perceptible walls or increased wall thickness on MRI, sometimes causing these lesions to be "upgraded." It was hypothesized that thickening of cyst walls on MRI can be artifactual, due to data truncation, applied filtering, ...
Newcombe Virginia F J VF University Division of Anaesthesia, Cambridge University, Addenbrooke's Hospital, Cambridge, United - - 2008
Magnetic resonance imaging and spectroscopy may provide important clinical information in the acute stages of brain injury. For this to occur it must be ensured that intracranial pressure (ICP) monitoring devices are safe to bring into the MR imaging suite. The authors tested a Codman MicroSensor ICP Transducer (Codman & ...
Noury Fanny - - 2008
Intervertebral disc (IVD) degeneration is a complex process characterized by biochemical and structural changes in both the nucleus pulposus and the anulus fibrosus. In this study, we were able to obtain in vivo magnetic resonance (MR) images of the rabbit spine, with several MR imaging (MRI) contrasts (rho, T(1) and ...
Diolaiuti Sara - - 2009
PURPOSE: To report the efficacy of percutaneous treatment of an orbital venous malformation with an electrolytically detachable fibred coil. METHODS: We report an instance of radiography-guided percutaneous treatment with an electrolytically detachable fibred coil in a 16-year-old boy with acute, spontaneous, painless proptosis on the left side, which progressed with ...
Strandberg Maria - - 2008
PURPOSE: To assess if 3T MRI can be further improved by adding surface coil imaging, in the context of detection and characterization of cerebral lesions in patients with drug-resistant epilepsy. METHODS: Twenty five patients with drug-resistant epilepsy undergoing evaluation for epilepsy surgery were examined with high resolution 3T MRI. The ...
Chung Seok Won - - 2008
In order to assess the incidence of thromboembolic events and their clinical presentations, the present study prospectively examined routine brain magnetic resonance images (MRI) taken within 48 hours after a coil embolization of cerebral aneurysms. From January 2006 to January 2008, 163 cases of coil embolization of cerebral aneurysm were ...
Schmitt Melanie M Department of Radiology, A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts 02129, - - 2008
A 128-channel receive-only array coil is described and tested for cardiac imaging at 3T. The coil is closely contoured to the body with a "clam-shell" geometry with 68 posterior and 60 anterior elements, each 75 mm in diameter, and arranged in a continuous overlapped array of hexagonal symmetry to minimize ...
Tsai L L - - 2008
We describe the design and operation of an open-access, very-low-field, magnetic resonance imaging (MRI) system for in vivo hyperpolarized 3He imaging of the human lungs. This system permits the study of lung function in both horizontal and upright postures, a capability with important implications in pulmonary physiology and clinical medicine, ...
Ulmer Stephan - - 2008
Magnetic resonance (MR) imaging in animal models is usually performed in expensive dedicated small bore animal scanners of limited availability. In the present study a standard clinical 1.5 T MR scanner was used for morphometric and dynamic contrast-enhanced susceptibility-weighted MR imaging (DSC-MRI) of a glioma model of the rat brain. ...
Mosca Frédéric - - 2008
The synthetic aperture imaging is a very promising solution in the well-known compromise between contrast and frame rate. Indeed this method leads to the measurement of each transmitterreceiver impulse response of the system. From this fact, synthetic aperture imaging reach the transmitreceive focus imaging quality for the cost in frame ...
Lohan Derek G - - 2008
MR imaging has been incorporated into the diagnostic algorithm for suspected thoracic aortic pathology, challenging CT and invasive catheter angiography as investigations of choice. Techniques, including spin echo, 3-D steady-state free precession, cardiac cine imaging, phase-contrast flow quantification, and high-resolution contrast-enhanced magnetic resonance angiography, are poised to trump other single ...
Koukos Ioannis - - 2008
In this paper we examine the classification of different seafloors based on the analysis of images obtained by side-scan sonar. For this purpose, we apply various two dimensional multilevel wavelet decomposition schemes on images obtained from three different seafloor types, i.e., sand ripples, rocks and sands, and then we examine ...
Zerr Benoit - - 2008
Seabed classification is key issue for civilian and military underwater applications, from offshore exploitation to mine counter measure. Most of the existing automated classification techniques relies on the analysis of the data provided by a single sensor, supposed to unambiguously separate the different classes of seabed. In this paper we ...
Noworolski Susan M SM Department of Radiology, University of California, San Francisco, San Francisco, California 94107, USA. - - 2008
To compare the data quality and ease of use of four endorectal-coil probe setups for prostate MRI. Four endorectal-coil probe setups were compared: 1) air-inflated probe; 2) perfluorocarbon (PFC)-inflated probe; 3) rigid, smaller prototype coil; and 4) rigid, smaller coil designed for biopsying the prostate. Signal-to-noise ratio (SNR), positioning, shimming, ...
Gorny Krzysztof R - - 2008
Calorimetric measurements were performed to determine the average specific absorption rates (SAR) resulting from MRI head examinations. The data were compared with average head coil SAR estimates displayed by the MR scanner in order to refine the imaging protocols used in imaging patients with implanted deep brain stimulators (DBS). The ...
Lin Fa-Hsuan FH MGH-HST Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA 02129, USA. - - 2008
Developments in multi-channel radio-frequency (RF) coil array technology have enabled functional magnetic resonance imaging (fMRI) with higher degrees of spatial and temporal resolution. While modest improvement in temporal acceleration has been achieved by increasing the number of RF coils, the maximum attainable acceleration in parallel MRI acquisition is intrinsically limited ...
Ozawa N - - 2008
Integration of intraoperative diffusion-weighted imaging (iDWI) into neuronavigation can be potentially useful for identification of the pyramidal tract during surgery for parenchymal brain lesions. The technique of iDWI using an intraoperative MR scanner of low magnetic field strength (0.3 Tesla) has been developed. For image acquisition, a specially designed solenoid ...
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