Dual energy basis decomposition techniques apply to single projection radiographic imaging. The high and low images are non‐linearly transformed generate two energy‐independent characterizing the integrated Compton/photoelectric attenuation components. Characteristic linear combinations of these identify unknown materials, cancel known synthesized monoenergetic images. problems intervening materials material displacement solved in general for a wide class clinical imaging tasks. angle...

Abstract Respiratory motion is a major limiting factor in improving image resolution and signal‐to‐noise ratio MR coronary imaging. In this work the effects of respiration on cardiac position were studied quantitively by imaging heart during diastole at various positions tidal with breath‐hold segmented fast gradient echo technique. It was found that breathing movement due to dominated superior‐inferior (SI) motion, which linearly related SI diaphragm. The approximately global translation....

Abstract A method of magnetic resonance image acquisition and reconstruction is described in which high imaging rates fast times are allowed. The a modification the basic FLASH sequence but with restricted number N phase encodings. encodings applied sequentially, periodically, continuously. Images formed by sliding window width along acquired data reconstructing an for each position window. In general time per exceeds between successive images, thus has temporal lag. Experimental studies...

PURPOSE: To describe a clinically useful application of functional magnetic resonance (MR) imaging--presurgical mapping the sensory motor cortex--and to validate results with established physiologic techniques. MATERIALS AND METHODS: Functional MR cortex was performed in two women, aged 24 and 38 years. Both had intractable, simple partial seizures due tumors located or near cortex. They subsequently underwent invasive cortical mapping--direct stimulation and/or sensory-evoked-potential...

MRI of brain ironB Drayer, P Burger, R Darwin, S Riederer, Herfkens and GA JohnsonAudio Available | Share

Several aspects of blipped echo-planar imaging (EPI) are treated mathematically. An expression relating the necessary readout gradient strength and sampling time to spatial resolution duration is derived. It shown how net may be limited by object's T2 characteristics B0 field homogeneity, irrespective number sampled points. Additionally, off-resonance effects result in a loss image distortion considerably greater degree than conventional two-dimensional Fourier transform imaging. The extent...

PURPOSE: To determine the reliability of obtaining arterial-phase, contrast-material-enhanced three-dimensional (3D) magnetic resonance (MR) angiograms renal arteries by using a technique that combines two-dimensional real-time MR fluoroscopy and 3D angiographic acquisition with elliptical centric view order. MATERIALS AND METHODS: Twenty-five consecutive patients suspected having artery disease were evaluated fluoroscopically triggered mean dose 0.18 mmol/kg gadoteridol. Left vein...

To evaluate fast fluid-attenuated inversion-recovery (FLAIR) technique for imaging brain abnormalities.A FLAIR sequence was developed that provided 36 5-mm contiguous sections in 5 minutes 8 seconds. Resulting images were compared with dual-echo T2-weighted spin-echo of 41 consecutive patients abnormalities.Contrast and contrast-to-noise ratios (C/Ns) (for contrast between the lesion background cerebrospinal fluid) exceeded corresponding values all but second-echo lesion-to-background C/N....

Abstract In this article we describe the precision in estimation of spin–lattice relaxation time TI from MRI signals acquired for various flip angles with repetition TR held constant. We review procedure itself and present a model propagation noise signal into calculated TI. This is verified by both Monte Carlo simulations experimental data taken on image phantoms. Based model, find that given TR/TI there exist two optimal will minimize uncertainty estimated also show how can be selected...

Abstract We describe a phase contrast based MRI technique with high sensitivity to cyclic displacement that is capable of quantitatively imaging acoustic strain waves in tissue‐like materials. A formalism for considering gradient waveforms as basis functions measure arbitrary motion introduced. Experiments agarose gel phantoms show it possible small displacements at submicron level by an appropriate choice the applied function and use this capability observe spatial temporal pattern caused...

The distribution of iron in the brain was analyzed using high field strength (1.5 T) magnetic resonance (MR) imaging 14 healthy control individuals and six patients with Parkinson plus syndromes (multisystem atrophy progressive supranuclear palsy) who were unresponsive to antiparkinsonian therapy. normal topographic as indicated by MR images coincided precisely determined Perls staining for ferric iron. In syndromes, there abnormally increased concentrations (decreased T2 relaxation times)...

An expression is derived showing that the two-dimensional noise power spectrum of computed X-ray tomography proportional to mod G(k) 2/k where k radial spatial frequency and one-dimensional corrective filter used in filtered back-projection reconstruction technique. It shown predicted spectra compare well with those estimated from CT reconstructions simulated for both ramp Hanning-weighted filter. A consequence non-uniform shape statistical correlated point point. Because this correlation...

Abstract Despite the fact that respiratory motion is a major factor limiting image quality of MR examinations in upper abdomen, little quantitative information available about kinematics visceral during respiration. The objective this study was to obtain measure relative longitudinal and transverse displacements abdominal organs breathing using an line scan technique. © 1992 Academic Press, Inc.

Abstract A single “orbital” navigator echo, that has a circular k ‐space trajectory, is used to simultaneously measure in‐plane rotational and multi‐axis translational global motion. Rotation determined from the shift in magnitude profile of echo with respect reference echo. Displacements are calculated phase difference between current Phantom studies show this technique can accurately rotation translations. Preliminary results adaptive motion correction on phantom human subjects indicate...

Abstract A technique is described that provides improved reproducibility of breath‐holding for MR image acquisition by monitoring the superior‐inferior (S/I) position diaphragm. The method incorporates detection level inspiration using an signal, rapid display to patient diaphragm enable breath‐hold adjustment, and triggering data once appropriate attained. response time system short, approximately 10 ms. Studies in six volunteers this demonstrate a considerable decrease S/I range over...

A general expression is derived for the noise due to photon counting statistics in computed X-ray tomography. The variance inversely proportional cube of resolution distance. For scanners using a water box, reconstructed image depends on number detected primary photons, summed over all angles, that have passed through element. Predictions this formula agree well with results computer simulations. It shown how can be used determine such parameters as required flux, detector rate, and dose,...

Vascular occlusive disease poses a threat to kidney viability, but whether the events leading injury and eventual fibrosis actually entail reduced oxygenation regional tissue ischemia is unknown. Answering this question has been difficult because of lack an adequate method assess in humans. BOLD (blood oxygen-level-dependent) magnetic resonance imaging detects changes deoxyhemoglobin during maneuvers that affect oxygen consumption, therefore technique was used image analyze cortical...

A computerized fluoroscopic system with dedicated real-time hard-wired algorithms can be used for cardiovascular imaging or without injection of iodine. Initial differentiated and integrated time subtraction displays are presented. Contrast studies appear adequate visualization dynamics. Cardiac images contrast material suggest expected blood flow patterns but difficult to interpret.

Iodine is commonly used as a contrast material in computerized x‐ray tomography. In some cases the determination of iodine distribution image may be prevented by presence bone or tissue variations within tomographic slice. This paper describes method for quantitative selective imaging concentration The employs scans using three heavily filtered beams, two having mean energies which straddle K edge (33 keV) and another at slightly higher energy. results are independent over broad range...

An important part of thermal ablation therapy is the assessment spatial extent tissue coagulation. In this work, mechanical properties thermally-ablated were quantitatively evaluated using magnetic resonance elastography (MRE). This study shows that focused ultrasound ablated are significantly different from normal tissue, and difference can be imaged measured MRE. Repeated experiments revealed a reproducible pattern property change during in ex vivo bovine muscle. may reflect changes...

Endoanal ultrasound identifies anal sphincter anatomy, and evacuation proctography visualizes pelvic floor motion during simulated defecation. These complementary techniques can evaluate obstructed defecation fecal incontinence. Our aim was to develop a single, nonionizing, minimally invasive modality image global anatomy motion.We studied six patients with incontinence seven The sphincters were imaged an endoanal magnetic resonance imaging (MRI) coil (five patients). MR fluoroscopy acquired...

Standard, MR spin-warp sampling strategies acquire data on a rectangular k-space grid. That method samples from the "corners" of k-space, i.e., that lie in region outside an ellipse just inscribed boundary. Illustrative calculations demonstrate corners contribute to useful resolution only if interpolation such as zero-filled reconstruction is used. The consequences this finding acquisition and windowing are discussed. A further implication result spatial images reconstructed with...

Abstract This work describes an interleaved echo planar imaging (EPI) method for use on a standard whole body scanner. The data acquisition is divided into two to eight repetitions rather than one two, as implemented by dedicated EPI systems. Interleaving allows the of lower sampling bandwidth with significant increase in signal‐to‐noise. also has advantages relative ease implementation, no need postprocessing remove image distortion, and shimming case‐by‐case basis. was applied applications...

Abstract An elliptical centric phase‐encoding (PE) order is applied to steady‐state 3DFT imaging as performed during a single breath‐hold or following contrast agent administration. In set of simulation, phantom, and in vivo experiments, this truly PE shown be both more resistant breathing artifact capable suppressing undesirable venous signals that can arise peak arterial enhancement than number other techniques are presently use. Unlike orders, the ordering changes with relative dimensions...