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Velocity Encoding
 
(VENC) A specialized technique used for encoding flow-velocities.
The velocity encoding value is given by:
VENC = pi / gamma DELTA M1.
Gamma is the gyromagnetic ratio, and DELTA M1 is the gradient moment and is proportional to the area of the flow encoding gradient waveform.

See also Phase Contrast Sequence, Phase Contrast Angiography, and Bipolar Gradient Pulse.
 
Images, Movies, Sliders:
 PCA-MRA 3D Brain Venography Colored MIP  Open this link in a new window
    

 
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• View the DATABASE results for 'Velocity Encoding' (2).Open this link in a new window

 
Further Reading:
  Basics:
Non-invasively Measuring Blood Flow Using Magnetic Resonance Imaging - NOVA™ Now Available In Europe
Wednesday, 1 October 2008   by www.medicalnewstoday.com    
Magnetic resonance flow velocity and temperature mapping of a shape memory polymer foam device
Thursday, 31 December 2009   by 7thspace.com    
Venetian Blind ArtifactInfoSheet: - Artifacts -
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Venetian blind
DESCRIPTION
Loss of signal of flowing blood
REASON
Saturation effect
HELP
Smaller 3D volume, multi chunk, TONE
The saturation effect of inflowing blood in 3D inflow MRA.
mri safety guidance
Image Guidance
Smaller 3D Volume or scans with e.g. tilt optimized nonsaturated excitation. In multi chunk scans TONE decreases this artifact or allows thicker chunks.
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• View the DATABASE results for 'Venetian Blind Artifact' (3).Open this link in a new window

 
Further Reading:
  Basics:
Magnetic Resonance Imaging (MRI)
2003   by www.hull.ac.uk    
MRI Resources 
Brain MRI - Intraoperative MRI - Manufacturers - Education - Abdominal Imaging - Shielding
 
Ventilation AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Inert hyperpolarized gases are under development for imaging air spaces, including those in the lungs. Because they mostly contain air and water, lungs are difficult organs to image.
These ventilation agents (gases) have potential in lung imaging and are currently used in studies of the pulmonary ventilation:
perfluorinated gases
aerosolized gadolinium-DTPA
hyperpolarized gases (xenon-129, helium-3)
molecular oxygen

Specific isotopes of inert gases can be hyperpolarized. Hyperpolarized is a state in which almost all of the atoms nuclei are spinning in the same direction. Once the nuclei in the isotope 3He have been hyperpolarized using a laser, they remain in this state for several days. The inert, hyperpolarized gas can then be used in a lung imaging study, where the high concentration of polarized nuclei provides a sharp contrast in MRI. The technique is already being developed with a view to commercialization by Magnetic Imaging Technologies in Durham, North Carolina. According to the company, existing MRI equipment can be used with a few minor modifications, along with a gas polarizer. The technique could provide early detection and monitoring of pulmonary disease.
Hyperpolarized 129Xe can also be used as a magnetic resonance tracer because of its MR-enhanced sensitivity combined with its high solubility. This isotope differs from 3He in that it can dissolve in the blood. Strong enhancement of the nuclear spin polarization of xenon in the gas phase can be achieved by optical pumping of rubidium and subsequent spin-exchange with the xenon nuclei. This technique can increase the magnetic resonance signal of xenon by five orders of magnitude, thus allowing NMR detection of xenon in very low concentration. MR spectroscopy and imaging of optically polarized xenon shows considerable potential for medical applications (see also back projection imaging).
Nycomed Amersham anticipated the market for inert gases in pulmonary imaging. The company obtained an exclusive license for the use of helium (He) and xenon (Xe) as MRI contrast agents. Currently, the US FDA has not yet approved the commercial distribution of inert gas imaging equipment, because the technique is still undergoing trials.
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• View the DATABASE results for 'Ventilation Agents' (3).Open this link in a new window

 
Further Reading:
  Basics:
New oxygen-enhanced MRI scan 'helps identify most dangerous tumours'
Thursday, 10 December 2015   by www.dailymail.co.uk    
Low-Field MRI of Laser Polarized Noble Gas
   by xenon.unh.edu    
  News & More:
Hyperpolarized Gas MRI for Pulmonary Disease Assessment: Interview with Richard Hullihen, CEO of Polarean Imaging
Wednesday, 9 September 2020   by www.medgadget.com    
Pumpkin-shaped molecule enables 100-fold improved MRI contrast: new agent for detecting pathological cells
Tuesday, 13 October 2015   by phys.org    
MRI Mapping of Cerebrovascular Reactivity via Gas Inhalation Challenges
Wednesday, 17 December 2014   by www.jove.com    
Using MRI to study gas reactions
Thursday, 31 January 2008   by www.theengineer.co.uk    
New Technique Reveals Insights Into Lung Disease
Thursday, 13 December 2007   by www.sciencedaily.com    
Very Small Superparamagnetic Iron Oxide ParticlesInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
(VSOP) A new class of contrast agents with smaller particle size than SPIO or USPIO with advantages for MR angiography, caused through a longer plasma half-life.

See also Ultrasmall Superparamagnetic Iron Oxide and Superparamagnetic Iron Oxide.
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• View the DATABASE results for 'Very Small Superparamagnetic Iron Oxide Particles' (3).Open this link in a new window

Vessel Separation
 
Postprocessing techniques for artery vein separation by segmentation of the entire vessel structures from the background with different approaches.
Phase contrast imaging can also be used to differentiate arteries and veins based on flow-velocity or flow direction. The fact that arterial and venous flows are in opposite directions also has the advantage to separate the vessels in time of flight angiography.
 
Images, Movies, Sliders:
 CE-MRA of the Carotid Arteries Colored MIP  Open this link in a new window
    
SlidersSliders Overview

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

 
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Further Reading:
  News & More:
Usefulness of non-contrast-enhanced magnetic resonance imaging prior to venous interventions
Tuesday, 18 September 2018   by www.ncbi.nlm.nih.gov    
MRI Resources 
Health - Universities - Directories - Non-English - IR - DICOM
 
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