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Result : Searchterm 'Nuclear Magnetic Resonance' found in 4 terms [ ] and 8 definitions [ ], (+ 8 Boolean[ ] results
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Magnetic resonance imaging ( MRI) is based on the magnetic resonance phenomenon, and is used for medical diagnostic imaging since ca. 1977 (see also MRI History).
The first developed MRI devices were constructed as long narrow tunnels. In the meantime the magnets became shorter and wider. In addition to this short bore magnet design, open MRI machines were created. MRI machines with open design have commonly either horizontal or vertical opposite installed magnets and obtain more space and air around the patient during the MRI test.
The basic hardware components of all MRI systems are the magnet, producing a stable and very intense magnetic field, the gradient coils, creating a variable field and radio frequency (RF) coils which are used to transmit energy and to encode spatial positioning. A computer controls the MRI scanning operation and processes the information.
The range of used field strengths for medical imaging is from 0.15 to 3 T. The open MRI magnets have usually field strength in the range 0.2 Tesla to 0.35 Tesla. The higher field MRI devices are commonly solenoid with short bore superconducting magnets, which provide homogeneous fields of high stability.
There are this different types of magnets:
The majority of superconductive magnets are based on niobium-titanium (NbTi) alloys, which are very reliable and require extremely uniform fields and extreme stability over time, but require a liquid helium cryogenic system to keep the conductors at approximately 4.2 Kelvin (-268.8° Celsius). To maintain this temperature the magnet is enclosed and cooled by a cryogen containing liquid helium (sometimes also nitrogen).
The gradient coils are required to produce a linear variation in field along one direction, and to have high efficiency, low inductance and low resistance, in order to minimize the current requirements and heat deposition. A Maxwell coil usually produces linear variation in field along the z-axis; in the other two axes it is best done using a saddle coil, such as the Golay coil.
The radio frequency coils used to excite the nuclei fall into two main categories; surface coils and volume coils.
The essential element for spatial encoding, the gradient coil sub-system of the MRI scanner is responsible for the encoding of specialized contrast such as flow information, diffusion information, and modulation of magnetization for spatial tagging.
An analog to digital converter turns the nuclear magnetic resonance signal to a digital signal. The digital signal is then sent to an image processor for Fourier transformation and the image of the MRI scan is displayed on a monitor.
For Ultrasound Imaging (USI) see Ultrasound Machine at Medical-Ultrasound-Imaging.com.
See also the related poll results: ' In 2010 your scanner will probably work with a field strength of' and ' Most outages of your scanning system are caused by failure of' | | | | | | | | | | | | | | Further Reading: | News & More:
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small-steps-can-yield-big-energy-savings-and-cut-emissions-mris Thursday, 27 April 2023 by www.itnonline.com |  |  |
Portable MRI can detect brain abnormalities at bedside Tuesday, 8 September 2020 by news.yale.edu |  |  |
Point-of-Care MRI Secures FDA 510(k) Clearance Thursday, 30 April 2020 by www.diagnosticimaging.com |  |  |
World's First Portable MRI Cleared by FDA Monday, 17 February 2020 by www.medgadget.com |  |  |
Low Power MRI Helps Image Lungs, Brings Costs Down Thursday, 10 October 2019 by www.medgadget.com |  |  |
Cheap, portable scanners could transform brain imaging. But how will scientists deliver the data? Tuesday, 16 April 2019 by www.sciencemag.org |  |  |
The world's strongest MRI machines are pushing human imaging to new limits Wednesday, 31 October 2018 by www.nature.com |  |  |
Kyoto University and Canon reduce cost of MRI scanner to one tenth Monday, 11 January 2016 by www.electronicsweekly.com |  |  |
A transportable MRI machine to speed up the diagnosis and treatment of stroke patients Wednesday, 22 April 2015 by medicalxpress.com |  |  |
Portable 'battlefield MRI' comes out of the lab Thursday, 30 April 2015 by physicsworld.com |  |  |
Chemists develop MRI technique for peeking inside battery-like devices Friday, 1 August 2014 by www.eurekalert.org |  |  |
New devices doubles down to detect and map brain signals Monday, 23 July 2012 by scienceblog.com |
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Magnetic resonance imaging
is a radiological diagnostic procedure without X-rays.
Magnetic resonance imaging, see also: MRI history, medical imaging, nuclear magnetic resonance, spin, precession, T1 time, T2 time, MRI equipment, MRI devices, MRI coils, MRI sequences, MRI contrast agents.
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( MRI) Magnetic resonance imaging is a noninvasive medical imaging technique that uses the interaction between radio frequency pulses, a strong magnetic field and body tissue to obtain images of slices/planes from inside the body. These magnets generate fields from approx. 2000 times up to 30000 times stronger than that of the Earth. The use of nuclear magnetic resonance principles produces extremely detailed pictures of the body tissue without the need for x-ray exposure and gives diagnostic information of various organs.
Measured are mobile hydrogen nuclei (protons are the hydrogen atoms of water, the 'H' in H 20), the majority of elements in the body. Only a small part of them contribute to the measured signal, caused by their different alignment in the magnetic field. Protons are capable of absorbing energy if exposed to short radio wave pulses (electromagnetic energy) at their resonance frequency. After the absorption of this energy, the nuclei release this energy so that they return to their initial state of equilibrium.
This transmission of energy by the nuclei as they return to their initial state is what is observed as the MRI signal. The subtle differing characteristic of that signal from different tissues combined with complex mathematical formulas analyzed on modern computers is what enables MRI imaging to distinguish between various organs. Any imaging plane, or slice, can be projected, and then stored or printed.
The measured signal intensity depends jointly on the spin density and the relaxation times ( T1 time and T2 time), with their relative importance depending on the particular imaging technique and choice of interpulse times. Any motion such as blood flow, respiration, etc. also affects the image brightness.
Magnetic resonance imaging is particularly sensitive in assessing anatomical structures, organs and soft tissues for the detection and diagnosis of a broad range of pathological conditions. MRI pictures can provide contrast between benign and pathological tissues and may be used to stage cancers as well as to evaluate the response to treatment of malignancies. The need for biopsy or exploratory surgery can be eliminated in some cases, and can result in earlier diagnosis of many diseases. See also MRI History and Functional Magnetic Resonance Imaging (fMRI). | | | |  | | • View the DATABASE results for 'Magnetic Resonance Imaging MRI' (9).
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