OBJECTIVE: To compare MR images of the triangular fibrocartilage complex (TFCC) using microscopy coils with those using a conventional surface coil qualitatively and quantitatively. DESIGN AND PATIENTS: Proton density-weighted images and T2*-weighted images of the TFCC from ten normal volunteers were obtained with a conventional surface coil (C4 coil; 80 ...

We compress phase-shift digital holograms (whole Fresnel fields) for the transmission of three-dimensional images. For real-time networking applications, the time required to compress can be as critical as the compression rate. We achieve lossy compression through quantization of both the real and imaginary streams, followed by a bit packing operation. ...

Localized versions of two-dimensional (2D) magnetic resonance spectroscopic (MRS) sequences, namely JPRESS and L-COSY, have been implemented on a whole-body 3T MRI/MRS scanner. Volume selection was achieved using three slice-selective radio-frequency (RF) pulses: 90 degrees-180 degrees-180 degrees in JPRESS and 90 degrees-180 degrees-90 degrees in L-COSY with a CHESS sequence ...

We consider the commonly used "Sum-of-Squares" (SoS) reconstruction method for phased-array magnetic resonance imaging with unknown coil sensitivities. We show that the signal-to-noise ratio (SNR) in the image produced by SoS is asymptotically (as the input SNR--> infinity ) equal to that of maximum-ratio combining, which is the best unbiased ...

The wide variety of available surface coils, pulse sequences, and post-processing techniques make MR imaging a useful clinical and research tool for evaluation of pelvic floor relaxation. Cases of isolated cystocele do not require imaging; however, in cases in which multiple compartments of the pelvis are involved or the patient ...

Magnetic resonance (MR) systems operating at 3 Telsa (T) and above have demonstrated considerable potential in human studies, offering improved signal-to-noise ratio and spectral resolution. However, because of radiofrequency limitations and concerns, and the lack of large volume body coils, most studies have been limited to the head. In this ...

Quantization of the coefficients within a discrete wavelet transform subband gives rise to distortions in the reconstructed image that are localized in spatial frequency and orientation and are spatially correlated with the image. We investigated the detectability of these distortions: Contrast thresholds were measured for both simple and compound distortions ...

PURPOSE: The aim of this work was to compare the knee coil and the surface coil for the visualisation of the patellar cartilage. MATERIALS AND METHODS: In 28 patients (17 women, 11 men) with an average age of 40 years (range 14-76) with knee pain MR was performed. Transverse images ...

In this paper I review our experiments on visualization of discrete breathers (intrinsic localized modes) in nonlinear lattices made of Josephson junctions. Properties of Josephson junctions and arrays made of such junctions are discussed in the Introduction. The visualization technique based on low temperature laser scanning microscopy (LSM) is described ...

Inductively coupled solenoid coils fitting to objects in the size of mice or rats were developed to adapt modem whole-body MR scanners featuring sufficient gradient strength for animal examinations with high spatial resolution. Homogenous receiver characteristics is achievable over almost the whole inner region of the solenoid coils. The SNR ...

PURPOSE: To examine peripheral nerve stimulation (PNS) thresholds for normal human subjects in magnetic resonance imaging (MRI) gradient coils, and determine if observed thresholds could be predicted based on gross physiologic measurements. MATERIALS AND METHODS: PNS thresholds for 21 healthy normal subjects were measured using a whole-body gradient coil. Subjects ...

The mechanical nature of gastric contraction activity (GCA) plays an important role in gastrointestinal motility. The aim of this study was to detect GCA in anaesthetized dogs, using simultaneously the techniques of AC biosusceptometry (ACB) and manometry, analysing the characteristics of frequency and amplitude (motility index) of GCA, modified by ...

A study of first-order Talbot resonators is presented. The general conditions for Talbot effect in ABCD systems are determined. These conditions are applied to the computation of the diffraction overlapping coefficients between array Gaussian emitters in a general first-order Talbot resonator. Relations on the ray-transfer matrix to generate the symmetric ...

Sensitivity encoding (SENSE) uses multiple MRI receive coil elements to encode spatial information in addition to traditional gradient encoding. Requiring less gradient encodings translates into shorter scan times, which is extremely beneficial in many clinical applications. SENSE is available to routine diagnostic imaging for the past 2 years. This paper ...

A high-frequency RF volume coil based on the use of microstrip transmission line (MTL) has been developed for in vivo 1H MR applications on the human head at 4T. This coil is characterized by major advantages: (i) completely distributed coil circuit, (ii) high-quality factor (Q), (iii) simple coil structure, and ...

Retrograde urethrography is the method commonly employed in the detection of anterior male urethra pathology. Ultrasonography and magnetic resonance imaging have been proposed recently as new methods that can replace conventional radiography. Normal urethral anatomy can be easily studied after saline distention of the urethra, which creates high contrast relative ...

PURPOSE: To investigate the efficacy of passive acoustic screening in the magnetic resonance (MR) environment by reducing direct and indirect MR-related acoustic noise, both from the patient's and health worker's perspective. MATERIALS AND METHODS: Direct acoustic noise refers to sound originating from the inner and outer shrouds of the MR ...

The use of detached endcaps for 3 T birdcage coils was investigated both theoretically and experimentally. Finite difference time domain analysis, along with workbench and MRI techniques, were used to map the radiofrequency (RF) B(1) distribution along the coil axis with and without an endcap. Without an endcap the measured ...

PURPOSE: To test the hypotheses that a single internal guide wire coil (i) permits independent and direct depiction of guide wires and catheters and (ii) improves catheter-tracking accuracy and depiction compared to external receiver coils. MATERIALS AND METHODS: Standard 5-6-F angiographic catheters were filled with dilute 4% gadolinium chelate. A ...

OBJECTIVE: MRI is being used to characterize the composition of atherosclerotic plaques. However, the resolution achievable using surface radiofrequency coils is limited by the signal to noise ratio. We studied the utility of a new intravascular (IV) MRI probe for high-resolution in vivo imaging of atherosclerotic lesions. METHODS AND RESULTS: ...

INTRODUCTION: While it is desirable to perform MRI examinations in patients with deep brain stimulators (DBS), a major safety concern exists regarding the potential for excessive heating secondary to magnetically induced electrical currents. This study was designed to determine the safety of MRI and DBS. METHODS: Standard configurations of DBS ...

A layered depth image (LDI) is a new popular representation and rendering method for objects with complex geometries. Similar to a two-dimensional (2-D) image, the LDI consists of an array of pixels. However, unlike the 2-D image, an LDI pixel has depth information, and there are multiple layers at a ...

Cavernous hemangioma of the rectum (CHR) is an uncommon benign vascular lesion, which mainly affects young adults. The rectosigmoid area is the most common site of cavernous hemangioma in the gastrointestinal tract. CHR is often misdiagnosed due to a lack of knowledge of the clinical features. We report a case ...

This paper describes the performance of the MPEG-4 still texture image codec in coding noisy images. As will be shown, when using the MPEG-4 still texture image codec to compress a noisy image, increasing the compression rate does not necessarily imply reducing the peak-signal-to-noise ratio (PSNR) of the decoded image. ...

Based on a local spatial/frequency representation,we employ a spectral histogram as a feature statistic for texture classification. The spectral histogram consists of marginal distributions of responses of a bank of filters and encodes implicitly the local structure of images through the filtering stage and the global appearance through the histogram ...

To provide effective contraception and protection against sexually transmitted disease, vaginal gels should maximally cover the cervical os and the vaginal epithelium before, during and after intercourse. To non-invasively monitor the intravaginal distribution of an applied intravaginal gel, we performed high-resolution magnetic resonance imaging (MRI) of the female pelvis before, ...

OBJECT: The authors report on a new head coil into which the Leksell aluminum localization frame can be easily and securely mounted. Mechanically, the head coil interferes little with the patient. METHODS: The head coil, which is for magnetic resonance (MR) imaging, is a 12-element quadrature transmit-and-receive high-pass birdcage coil ...

BACKGROUND: An electronic radial array echoendoscope has been developed that uses the same US processor as the linear array instruments made by the same company, thereby eliminating the need for two processors. The performance of this prototype instrument was compared with that of a mechanical radial echoendoscope in patients. METHODS: ...

Radio-frequency (RF) coils are a necessary component of magnetic resonance imaging (MRI) systems. When used in transmit operation, they act to generate a homogeneous RF magnetic field within a volume of interest and when in receive operation, they act to receive the nuclear magnetic resonance signal from the RF-excited specimen. ...

We present an imaging technique to measure static surface displacements of electronic components. A device is supplied by a transient current that creates a variation of temperature, thus a surface displacement. To measure the latter, a setup that is based on a Michelson interferometer is used. To avoid the phenomenon ...

A technique for performing whole-body magnetic resonance (MR) angiography with multi-station three-dimensional MR angiography by using a self-developed rolling table platform that integrates the surface coil was evaluated in three volunteers and 10 patients. Use of the surface coil resulted in high signal-to-noise and contrast-to-noise ratios, which translated into sensitivity ...

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind-a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI's focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with ...

This study was performed to determine the location of a silicone rubber vaginal barrier contraceptive device, the Lea's Shield, in vivo. Two women, one parous and one nulligravid, were enrolled in the study. Surface coil, multiplanar Magnetic Resonance Imaging (MRI) was performed immediately following insertion of the contraceptive device, and ...

PURPOSE: To assess magnetic resonance imaging (MRI)-related heating for a neurostimulation system (Activa Tremor Control System, Medtronic, Minneapolis, MN) used for chronic deep brain stimulation (DBS). MATERIALS AND METHODS: Different configurations were evaluated for bilateral neurostimulators (Soletra Model 7426), extensions, and leads to assess worst-case and clinically relevant positioning scenarios. ...

PURPOSE: To investigate the ability of magnetic resonance imaging (MRI) to visualize the carotid vessel wall using a phased-array coil and a black-blood (BB) fast spin-echo (FSE) sequence. MATERIALS AND METHODS: The phased-array coil was compared with a three-inch coil. Images from volunteers were evaluated for artifacts, wall layers, and ...

Li and Zaidi (Vision Research 40 (2000) 217; 41 (2001) 1519) have recently argued that there are two necessary conditions for the perception of 3D shape from texture: (1) the texture pattern must have a disproportionate amount of energy along directions of principal curvature; and (2) the surface must be ...

In one volunteer, five breast coils were evaluated for signal-to-noise ratio (SNR), uniformity, comfort, subject orientation, access to the breast, and unilateral imaging options. The four-coil arrays provided superior SNR, imaging flexibility, and access. Uniformity and comfort were issues with all coils. Substantial design differences exist between coils; purchasers should ...

STUDY OBJECTIVE: To take recent progress in magnetic resonance imaging (MRI) into account to determine its accuracy compared with that of transvaginal ultrasonography (TVUS) in diagnosing bladder endometriosis. DESIGN: Retrospective analysis (Canadian Task Force classification II-2). SETTING: University-affiliated hospital. PATIENTS: Twelve women with histologically proved bladder endometriosis. INTERVENTION: Magnetic resonance ...

A new method for acquiring MR data in two dimensions is described. This is achieved by combining coils into an array so as to produce a unique local magnetic field within each coil when placed within the B(0) field of a standard MRI scanner. In this way each known location ...

Parallel magnetic resonance imaging (MRI) techniques use spatial information from arrays of radiofrequency (RF) detector coils to accelerate imaging. A number of parallel MRI techniques have been described in recent years, and numerous clinical applications are currently being explored. The advent of practical parallel imaging presents various challenges for image ...

An inverse methodology is described to assist in the design of radio-frequency (RF) coils for magnetic resonance imaging (MRI) applications. The time-harmonic electromagnetic Green's functions are used to calculate current on the coil and shield cylinders that will generate a specified internal magnetic field. Stream function techniques and the method ...

In 15 volunteers and 84 patients with clinically suspected peripheral vascular disease, a stepping kinematic imaging platform, a manual retrofit stepping magnetic resonance (MR) imaging table, was used with three high-field-strength MR imaging systems to perform multistation peripheral contrast material-enhanced MR angiography in the lower extremity with the existing system ...

We examine the rate-distortion performance and computational complexity of linear transforms for lossy data compression. The goal is to better understand the performance/complexity tradeoffs associated with using the Karhunen-Loeve transform (KLT) and its fast approximations. Since the optimal transform for transform coding is unknown in general, we investigate the performance ...

A new predictive technique for lossless compression is applied to CT and MR images in order to achieve high compression in the lossless mode. To accomplish this, a prediction value was obtained by assuming the horizontal and vertical components of each pixel. Wide and narrow predictive coding modes were adaptively ...

Fast scan techniques, which are used to reduce scanning times, have raised scanning noise levels in magnetic resonance imaging (MRI) systems, resulting in greater patient discomfort and stress. It is well known that this noise is caused by vibration of the gradient coil due to the Lorentz forces generated by ...

An inductively coupled implanted coil was designed for high-resolution magnetic resonance (MR) studies of rat spinal cord (SC) in vivo at 7 T. The practical issues involved in implementation of the coil at high fields are discussed, and the adjustment of various parameters for optimizing coil performance are described. The ...

Steady fluid flow was studied in a simple bifurcation model and in a physiologically realistic model of the human carotid bifurcation. Wall shear stress (WSS) vectors were calculated from phase-contrast (PC) magnetic resonance imaging (MRI) measurements of the velocity field. Velocity measurements in the inflow regions were also used as ...

The feasibility of in vivo high-resolution magnetic resonance micro-imaging of fine anatomic structures of human toes was tested. Five healthy subjects were investigated on an experimental 3 Tesla whole body scanner, using standard 3D gradient echo sequences. A radio-frequency surface coil was used for signal detection. Feet, toes and surface ...

Radio-frequency coils play a crucial role in the quest for optimal magnetic resonance (MR) image resolution. Given the growing variety of specialized coils available for neuroradiologic imaging applications, it is critical that radiologists use a coherent strategy for successfully matching these coils to specific imaging situations. First, fundamental concepts of ...

Pulsed magnetic field gradients in magnetic resonance imaging produce high levels of acoustic noise. In functional magnetic resonance imaging, acoustic scanner noise causes unwanted masking effects. Recently, we proposed a method to perform magnetic resonance imaging experiments undisturbed by acoustic scanner noise by utilizing the property of standard gradient coils ...