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MRI Procedure
 
The MRI device is located within a specially shielded room (Faraday cage) to avoid outside interference, caused by the use of radio waves very close in frequency to those of ordinary FM radio stations.
The MRI procedure can easily be performed through clothing and bones, but attention must be paid to ferromagnetic items, because they will be attracted from the magnetic field. A hospital gown is appropriate, or the patient should wear clothing without metal fasteners and remove any metallic objects like hairpins, jewelry, eyeglasses, clocks, hearing aids, any removable dental work, lighters, coins etc., not only for MRI safety reasons. Metal in or around the scanned area can also cause errors in the reconstructed images (artifacts). Because the strong magnetic field can displace, or disrupt metallic objects, people with an implanted active device like a cardiac pacemaker cannot be scanned under normal circumstances and should not enter the MRI area.
The MRI machine can look like a short tunnel or has an open MRI design and the magnet does not completely surround the patient. Usually the patient lies on a comfortable motorized table, which slides into the scanner, depending on the MRI device, patients may be also able to sit up. If a contrast agent is to be administered, intravenous access will be placed. A technologist will operate the MRI machine and observe the patient during the examination from an adjacent room. Several sets of images are usually required, each taking some minutes. A typical MRI scan includes three to nine imaging sequences and may take up to one hour. Improved MRI devices with powerful magnets, newer software, and advanced sequences may complete the process in less time and better image quality.
Before and after the most MRI procedures no special preparation, diet, reduced activity, and extra medication is necessary. The magnetic field and radio waves are not felt and no pain is to expect.
Movement can blur MRI images and cause certain artifacts. A possible problem is the claustrophobia that some patients experience from being inside a tunnel-like scanner. If someone is very anxious or has difficulty to lie still, a sedative agent may be given. Earplugs and/or headphones are usually given to the patient to reduce the loud acoustic noise, which the machine produces during normal operation. A technologist observes the patient during the test. Some MRI scanners are equipped with televisions and music to help the examination time pass.
MRI is not a cheap examination, however cost effective by eliminating the need for invasive radiographic procedures, biopsies, and exploratory surgery. MRI scans can also save money while minimizing patient risk and discomfort. For example, MRI can reduce the need for X-ray angiography and myelography, and can eliminate unnecessary diagnostic procedures that miss occult disease.

See also Magnetic Resonance Imaging MRI, Medical Imaging, Cervical Spine MRI, Claustrophobia, MRI Risks and Pregnancy.
For Ultrasound Imaging (USI) see Ultrasound Imaging Procedures at Medical-Ultrasound-Imaging.com.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'
 
Images, Movies, Sliders:
 Brain MRI Images Axial T2  Open this link in a new window
      

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
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 CE-MRA of the Carotid Arteries  Open this link in a new window
    
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 Breast MRI Images T2 And T1 Pre - Post Contrast  Open this link in a new window
 Sagittal Knee MRI Images T1 Weighted  Open this link in a new window
      

 
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• Related Searches:
    • MRI Safety
    • MRI History
    • Liver Imaging
    • Spine MRI
    • Contrast Medium
 
Further Reading:
  News & More:
MRI technology visualizes heart metabolism in real time
Friday, 18 November 2022   by medicalxpress.com    
Are synthetic contrast-enhanced breast MRI images as good as the real thing?
Friday, 18 November 2022   by healthimaging.com    
Ultrafast MRI protocol reduces scan time by 10 minutes for cervical imaging
Monday, 26 September 2022   by healthimaging.com    
Study: Fast MRI can diagnose TBI without radiation
Wednesday, 18 September 2019   by www.aappublications.org    
Metamaterials boost sensitivity of MRI machines
Thursday, 14 January 2016   by www.eurekalert.org    
Working with MRI machines may cause vertigo: Study
Wednesday, 25 June 2014   by www.cos-mag.com    
Searchterm 'Artifact' was also found in the following services: 
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Radiology  (4) Open this link in a new windowUltrasound  (60) Open this link in a new window
Magnetic Resonance Angiography MRAMRI Resource Directory:
 - MRA -
 
(MRA) Magnetic resonance angiography is a medical imaging technique to visualize blood filled structures, including arteries, veins and the heart chambers. This MRI technique creates soft tissue contrast between blood vessels and surrounding tissues primarily created by flow, rather than displaying the vessel lumen. There are bright blood and black blood MRA techniques, named according to the appearance of the blood vessels. With this different MRA techniques both, the blood flow and the condition of the blood vessel walls can be seen. Flow effects in MRI can produce a range of artifacts. MRA takes advantage of these artifacts to create predictable image contrast due to the nature of flow.
Technical parameters of the MRA sequence greatly affect the sensitivity of the images to flow with different velocities or directions, turbulent flow and vessel size.
This are the three main types of MRA:
All angiographic techniques differentially enhance vascular MR signal. The names of the bright blood techniques TOF and PCA reflect the physical properties of flowing blood that were exploited to make the vessels appear bright. Contrast enhanced magnetic resonance angiography creates the angiographic effect by using an intravenously administered MR contrast agent to selectively shorten the T1 of blood and thereby cause the vessels to appear bright on T1 weighted images.
MRA images optimally display areas of constant blood flow-velocity, but there are many situations where the flow within a voxel has non-uniform speed or direction. In a diseased vessel these patterns are even more complex. Similar loss of streamline flow occurs at all vessel junctions and stenoses, and in regions of mural thrombosis. It results in a loss of signal, due to the loss of phase coherence between spins in the voxel.
This signal loss, usually only noticeable distal to a stenosis, used to be an obvious characteristic of MRA images. It is minimized by using small voxels and the shortest possible TE. Signal loss from disorganized flow is most noticeable in TOF imaging but also affects the PCA images.
Indications to perform a magnetic resonance angiography (MRA):
•
Detection of aneurysms and dissections
•
Evaluation of the vessel anatomy, including variants
•
Blockage by a blood clot or stenosis of the blood vessel caused by plaques (the buildup of fat and calcium deposits)

Conventional angiography or computerized tomography angiography (CT angiography) may be needed after MRA if a problem (such as an aneurysm) is present or if surgery is being considered.

See also Magnetic Resonance Imaging MRI.
 
Images, Movies, Sliders:
 CE-MRA of the Carotid Arteries Colored MIP  Open this link in a new window
    
SlidersSliders Overview

 CE MRA of the Aorta  Open this link in a new window
    
SlidersSliders Overview

 TOF-MRA Circle of Willis Inverted MIP  Open this link in a new window
    

 PCA-MRA 3D Brain Venography Colored MIP  Open this link in a new window
    

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 
Radiology-tip.comradCT Angiography,  Angiogram
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Medical-Ultrasound-Imaging.comVascular Ultrasound,  Intravascular Ultrasound
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• View the DATABASE results for 'Magnetic Resonance Angiography MRA' (3).Open this link in a new window


• View the NEWS results for 'Magnetic Resonance Angiography MRA' (10).Open this link in a new window.
 
Further Reading:
  Basics:
Magnetic resonance angiography: current status and future directions
Wednesday, 9 March 2011   by www.jcmr-online.com    
MR–ANGIOGRAPHY(.pdf)
  News & More:
3-D-printed model of stenotic intracranial artery enables vessel-wall MRI standardization
Friday, 14 April 2017   by www.eurekalert.org    
Conventional MRI and MR Angiography of Stroke
2012   by www.mc.vanderbilt.edu    
MR Angiography Highly Accurate In Detecting Blocked Arteries
Thursday, 1 February 2007   by www.sciencedaily.com    
MRI Resources 
Health - Journals - Calculation - Education pool - MRI Reimbursement - Societies
 
Magnetic SusceptibilityForum -
related threads
 
(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    
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Multiple Overlapping Thin Slab (Slice) Acquisition
 
(MOTSA) This technique combines the best features of 2D time of flight angiography (2D TOF) and 3D TOF MRA. The MOTSA technique consists of multiple 2 cm thick 3D TOF slabs (which minimize saturation effects for through plane flow) combine to provide unlimited coverage similar to multiple 2D TOF slices. High resolution imaging of the carotid arteries is possible when image quality is of greater concern than acquisition time. Images with 1 mm (or less) spatial resolution in all three planes are required. The slabs typically overlap 25-40 to minimize the venetian blind artifact venetian blind artifact due to minimal saturation effects. MOTSA is an useful technique for the evaluation of vertebrobasilar ischemia and aneurysm scanning from the foramen magnum through the circle of Willis.
 
Images, Movies, Sliders:
 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 
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Searchterm 'Artifact' was also found in the following services: 
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Respiratory Ordered Phase Encoding
 
Respiratory synchronization that acquires image data at regular times independent of the respiratory cycle, but chooses the sequence of phase encoding data acquisition so as to minimize the respiratory motion-induced artifacts in the resulting image. For example, choosing the sequence of phase encoding such that adjacent samples in the final full data set have minimal differences in respiratory phase will minimize the spacing of ghosting artifacts in the final image.
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• View the DATABASE results for 'Respiratory Ordered Phase Encoding' (5).Open this link in a new window

MRI Resources 
NMR - Abdominal Imaging - Diffusion Weighted Imaging - Case Studies - Safety Training - Examinations
 
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MRI is trending to low field magnets :
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