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Result : Searchterm 'Susceptibility' found in 3 terms [] and 43 definitions []
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Searchterm 'Susceptibility' was also found in the following services: 
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SusceptibilityForum -
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See Magnetic Susceptibility.
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    • Out of Phase
    • Susceptibility Artifact
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    • Chemical Shift
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  Basics:
Abdominal MRI at 3.0 T: The Basics Revisited
Wednesday, 20 July 2005   by www.ajronline.org    
Principles, Techniques, and Applications of T2*- based MR Imaging and Its Special Applications1
September 2009   by pubs.rsna.org    
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Ultrashort echo time (UTE) MRI of the spine in thalassaemia
February 2004   by bjr.birjournals.org    
Technical Assessment of Artifact Production from Neuro Endovascular Coil At 3 Tesla MRI: An In Vitro Study
2012   by www.tmps.or.th    
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Safety pool - Spectroscopy - Brain MRI - Equipment - Health - Process Analysis
 
Magnetic SusceptibilityForum -
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(c) Magnetic susceptibility is the degree of magnetization of a material in response to a magnetic field. Paramagnetic materials strengthen the magnetic field, diamagnetic materials weaken it. The magnetic susceptibility of ferromagnetic substances is not linear; this is called differential susceptibility.
Differences in magnetic susceptibilities are a frequent cause of MRI artifacts.
See also Susceptibility Artifact, Magnetism, Diamagnetism, Paramagnetism, Ferromagnetism.
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• View the DATABASE results for 'Magnetic Susceptibility' (15).Open this link in a new window

 
Further Reading:
  Basics:
Metal-Induced Artifacts in MRI
   by www.ajronline.org    
Magnetic susceptibility
   by en.wikipedia.org    
MRI Resources 
Mobile MRI - Manufacturers - MRI Technician and Technologist Schools - Mass Spectrometry - PACS - Veterinary MRI
 
Susceptibility ArtifactInfoSheet: - Artifacts - 
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 - Artifacts -
 
Quick Overview
Artifact Information
NAME Metal artifact, clip artifact, magnetic susceptibility artifact
DESCRIPTION Signal dropout, bright spots, spatial distortion
REASON Field inhomogeneity
HELP Remove the metal, do not take a gradient echo sequence, take a short echo time

Materials with magnetic susceptibility cause this artifact. There are in general three kinds of materials with magnetic susceptibility: ferromagnetic materials (iron, nickel etc.) with a strong influence and paramagnetic/diamagnetic (aluminium, platinum etc./gold, water, most organic compounds etc.) materials with a minimal/non influence on magnetic fields. In MRI, susceptibility artifacts are caused for example by medical devices in or near the magnetic field or by implants of the patient. These materials with magnetic susceptibility distort the linear magnetic field gradients, which results in bright areas (misregistered signals) and dark areas (no signal) nearby the magnetic material.


Image Guidance
Use a spin echo or a fast spin echo sequence, because gradient echo sequences are more sensitive to susceptibility artifacts. A high bandwidth (small water fat shift) and a short echo time help also to reduce this artifact.
In some cases it is even beneficial to use a gradient echo sequence, e.g. a cavernom contains some iron-rich haemosiderin, which also causes a signal void on gradient echo sequences and for this purpose increases the diagnostic image quality.
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• View the DATABASE results for 'Susceptibility Artifact' (8).Open this link in a new window

 
Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
Susceptibility Artifacts
   by www.mritutor.org    
  News & More:
Metal Artefact Reduction
Thursday, 9 June 2011   by www.revisemri.com    
Ultrashort echo time (UTE) MRI of the spine in thalassaemia
February 2004   by bjr.birjournals.org    
Searchterm 'Susceptibility' was also found in the following services: 
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Metal ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview

Artifact Information
NAME Metal, susceptibility
DESCRIPTION Signal dropout, bright spots
REASON Field inhomogeneity
HELP Remove the metal

Ferromagnetic metal will cause a magnetic field inhomogeneity, which in turn causes a local signal void, often accompanied by an area of high signal intensity, as well as a distortion of the image. They create their own magnetic field and dramatically alter precession frequencies of protons in the adjacent tissues. Tissues adjacent to ferromagnetic components become influenced by the induced magnetic field of the metal hardware rather than the parent field and, therefore, either fail to precess or do so at a different frequency and hence do not generate useful signal. Two components contribute to susceptibility artifact, induced magnetism in the ferromagnetic component itself and induced magnetism in protons adjacent to the component.
Artifacts from metal may have varied appearances on MRI scans due to different type of metal or configuration of the piece of metal. The biocompatibility of metallic alloys, stainless steel, cobalt chrome and titanium alloy is based on the presence of a constituent element within the alloy that has the ability to form an adherent oxide coating that is stable, chemically inert and hence biocompatible. In relation to imaging titanium alloys are less ferromagnetic than both cobalt and stainless steel, induce less susceptibility artifact and result in less marked image degradation.


Image Guidance
Remove the metal when possible or take a not so sensitive sequence (a SE or another sequence with a rephasing 180° pulse). See also Susceptibility Artifact.
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• View the DATABASE results for 'Metal Artifact' (2).Open this link in a new window

 
Further Reading:
  Basics:
Metal-Induced Artifacts in MRI
   by www.ajronline.org    
Metal Artefact Reduction
Thursday, 9 June 2011   by www.revisemri.com    
MRI Resources 
Blood Flow Imaging - Process Analysis - Portals - Mobile MRI - Research Labs - Non-English
 
Blood Oxygenation Level Dependent ContrastInfoSheet: - Sequences - 
Intro, 
Overview, 
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 - Functional MRI -
 
(BOLD) In MRI the changes in blood oxygenation level are visible. Oxyhaemoglobin (the principal haemoglobin in arterial blood) has no substantial magnetic properties, but deoxyhaemoglobin (present in the draining veins after the oxygen has been unloaded in the tissues) is strongly paramagnetic. It can thus serve as an intrinsic paramagnetic contrast agent in appropriately performed brain MRI. The concentration and relaxation properties of deoxyhaemoglobin make it a susceptibility , e.g. T2 relaxation effective contrast agent with little effect on T1 relaxation.
During activation of the brain, the oxygen consumption of the local tissue increase by approximately 5% with that the oxygen tension will decrease. As a consequence, after a short period of time vasodilatation occurs, resulting in a local increase of blood volume and flow by 20 - 40%. The incommensurate change in local blood flow and oxygen extraction increases the local oxygen level.
By using T2 weighted gradient echo EPI sequences, which are highly susceptibility sensitive and fast enough to capture the three-dimensional nature of activated brain areas will show an increase in signal intensity as oxyhaemoglobin is diamagnetic and deoxyhaemoglobin is paramagnetic. Other MR pulse sequences, such as spoiled gradient echo pulse sequences are also used.
As the effects are subtle and of the order of 2% in 1.5 T MR imaging, sophisticated methodology, paradigms and data analysis techniques have to be used to consistently demonstrate the effect.
As the BOLD effect is due to the deoxygenated blood in the draining veins, the spatial localization of the region where there is increased blood flow resulting in decreased oxygen extraction is not as precisely defined as the morphological features in MRI. Rather there is a physiological blurring, and is estimated that the linear dimensions of the physiological spatial resolution of the BOLD phenomenon are around 3 mm at best.

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Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
High-Resolution, Spin-Echo BOLD, and CBF fMRI at 4 and 7 T(.pdf)
October 2002   by otg.downstate.edu    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
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July 2002
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Musculoskeletal and Joint MRI - Lung Imaging - Directories - Fluorescence - Hospitals - Abdominal Imaging
 
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