PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 12081437

Short planar gradient coils for MR microscopy using concentric return paths.

Stephen J Dodd·Chien Ho
View original source ↗Export metadata ↓

Abstract

The aim of this work is to design a set of gradient coils with an optimal geometry for magnetic resonance microscopy studies. Designs for a three-axis gradient coil system particularly suited for studies with small radiofrequency coils are presented. The novel geometry involves a planar section with concentric return paths to keep the coil short. Reduction of the external field has been attempted by varying the positions of the return paths using a simulated annealing algorithm. A biplanar version of x- and z-directed prototype gradients was built and tested. A 2D-MR image of a grid phantom has been obtained on a 7-T MR instrument to demonstrate the theory. A three-axis set used as a surface gradient set has also been built and used to obtain high-resolution MR images.

Explore related subjects

Equipment DesignMagnetic Resonance ImagingMagneticsMathematicsMicroscopyPhantoms, ImagingJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Stephen J Dodd, Chien Ho. 2002. Short planar gradient coils for MR microscopy using concentric return paths.. https://doi.org/10.1006/jmre.2002.2532

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2003

Microchip PCR.

Miniaturization of genetic tests has become an important goal. This review surveys the current progress towards the miniaturization of tests based on the polymerase chain reaction (PCR). It examines the different types of PCR microchip designs, fabrication methods,and the components of a microchip PCR device. It also discusses the problems attributable to surface chemistry of microchip components (inhibition of PCR), and the static and dynamic surface passivation strategies developed for the solution of these difficulties

Equipment Design↗
PubMed2003

Fluid leakage past tracheal tube cuffs: evaluation of the new Microcuff endotracheal tube.

OBJECTIVE: This study compared the recently introduced Microcuff endotracheal tube HVLP ICU featuring an ultrathin (7-microm) polyurethane cuff membrane with endotracheal tubes from different manufacturers regarding fluid leakage past the tube cuff. DESIGN: In vitro setup. MEASUREMENTS AND RESULTS: The following endotracheal tubes (ID 7.5 mm) were compared: Mallinckrodt HiLo, Microcuff HVLP ICU, Portex Profile Soft Seal, Rüsch Super Safety Clear, and Sheridan CF. A vertical PVC trachea model (ID 20 mm) was intubated, and cuffs were inflated to 10, 15, 20, 25, 30, and 60 cmH2O. Colored water (5 ml) was added to the top of the cuff. The amount of leaked fluid past the tube cuff within 5, 10, and 60 min was recorded. Experiments were performed four times using two examples of each tube brand. Fluid leakage past tube cuffs occurred in all conventional endotracheal tubes at cuff pressures from 10 to 60 cmH2O. In the Microcuff tube cuff pressure fluid leakage was observed within 10 min only at 10 cmH2O. Results with the Microcuff tube were significantly better than all other tube brands at cuff pressures of 10-30 cmH2O. CONCLUSIONS: Within the acceptable upper limit for tracheal cuff pressure (25-30 cmH2O) the Microcuff endotracheal tube was the only one of the tested tubes to prevent fluid leakage in our in vitro setup. In vivo studies are required to confirm these findings.

Equipment Design↗
PubMed2003

Sitting comfort and discomfort and the relationships with objective measures.

The concepts of comfort and discomfort in sitting are under debate. There is no widely accepted definition, although it is beyond dispute that comfort and discomfort are feelings or emotions that are subjective in nature. Yet, beside several subjective methodologies, several objective methods (e.g. posture analysis, pressure measurements, electromyography (EMG) are in use to assess sitting comfort or discomfort. In the current paper a theoretical framework is presented, in which comfort and discomfort were defined and the hypothetical associations with underlying factors were indicated. Next, the literature was reviewed to determine the relationships between objective measures and subjective ratings of comfort and discomfort. Twenty-one studies were found in which simultaneous measures of an objective parameter and a subjective rating of comfort or discomfort were obtained. Pressure distribution appears to be the objective measure with the most clear association with the subjective ratings. For other variables, regarding spinal profile or muscle activity for instance, the reported associations are less clear and usually not statistically significant.

Equipment Design↗