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Result : Searchterm 'Flow' found in 15 terms [] and 98 definitions []
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Searchterm 'Flow' was also found in the following services: 
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Phase Contrast AngiographyMRI Resource Directory:
 - MRA -
 
(PCA) With this method images of the blood flow-velocity (or any other movement of tissue) are produced. The MRI signal contains both amplitude and phase information. The phase information can be used with subtraction of images with and without a velocity encoding gradient. The signal will be directly proportional to the velocity because of the relation between blood flow-velocity and signal intensity.
This is the strength of PCA, complete suppression of stationary tissue (no velocity - no signal), the direct velocity of flow is being imaged, while in TOF (Inflow) angiography, tissue with short T1 (fat or methaemoglobin) might be visualized.
The strength of the gradient determines the sensitivity to flow. It is set by setting the aliasing or encoding velocity (VENC). Unfortunately, phase sensitization can only be acquired along one axis at a time. Therefore, phase contrast angiographic techniques tend to be 4 times slower than TOF techniques with the same matrix.

See also Phase Contrast Sequence, Magnetic Resonance Angiography, Contrast Enhanced Magnetic Resonance Angiography, Flow Effects and Flow Quantification.
 
Images, Movies, Sliders:
 PCA-MRA 3D Brain Venography Colored MIP  Open this link in a new window
    

 
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• Related Searches:
    • Magnetic Resonance Angiography
    • Velocity
    • Phase Contrast Sequence
    • Bipolar Gradient Pulse
    • Contrast Enhanced Magnetic Resonance Angiography
 
Further Reading:
  Basics:
Magnetic resonance angiography: current status and future directions
Wednesday, 9 March 2011   by www.jcmr-online.com    
  News & More:
MR–ANGIOGRAPHY(.pdf)
Searchterm 'Flow' was also found in the following services: 
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Entry Slice Phenomenon (Artifact)InfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Entry slice phenomenon
DESCRIPTION
Bright signals in blood vessels at the first slice
REASON
Unsaturated spins
The entry slice phenomenon arise in MRI when blood with unsaturated spins flows in the observed slice(s). These spins will emit a strong signal, because of their unsaturated status (flow related enhancement). The number of slices affected depends on the flow velocity and the slice thickness; the direction of flow determines which slices are affected. Time of Flight MRA is based on this entry slice phenomenon.

See also Flow Compensation, Flow Related Enhancement, Artifact Overview and Artifacts Reduction Index.
 
Images, Movies, Sliders:
 TOF-MRA Circle of Willis Inverted MIP  Open this link in a new window
    

 
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Further Reading:
  News & More:
Troubleshooting the ACR MRI Accreditation Phantom Tests
   by www.aapm.org    
MRI Resources 
Services and Supplies - MRI Training Courses - Colonography - Open Directory Project - MRCP - Education pool
 
Cerebro Spinal Fluid Pulsation ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Cerebro spinal fluid pulsation
DESCRIPTION
Ghosting
REASON
Inconsistencies in phase and amplitude
Pulsatile cerebro spinal fluid flow produces ghost artifacts that are superimposed in the image.
mri safety guidance
Image Guidance
Flow compensation should be used to reduce these artifacts. This applies an additional gradient to eliminate phase differences for both stationary and moving spins at the echo time. At TE no phase differences is measured. If flow compensation is applied and there are still flow artifacts, cardiac triggering is an additional option to reduce these artifacts.
See also Motion Artifact.
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• View the DATABASE results for 'Cerebro Spinal Fluid Pulsation Artifact' (3).Open this link in a new window

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Gradient Motion Rephasing
 
(GMR) The application of strategic gradient pulses can compensate the objectionable spin phase effects of flow motion. That means the reducing of flow effects, e.g. gradient moment nulling of the first order of flow. The simplest velocity-compensated pulse sequence is the symmetrical second echo of a spin echo pulse sequence.
Gradient field changes can be configured in such a way that during an echo the magnetization signal vectors for all pixels have zero phase angle independent of velocities, accelerations etc. of the measured tissue. E.g. the adjustment to zero at the time TE of the net moments of the amplitude of the waveform of the magnetic field gradients with time. The zeroth moment is the area under the curve, the first moment is the 'center of gravity' etc. The aim is to minimize the phase shifts acquired by the transverse magnetization of excited nuclei moving along the gradients (including the effect of refocusing RF pulses), particularly for the reduction of image artifacts due to motion.
Also called Flow Compensation (FC), Motion Artifact Suppression Technique (MAST), Flow motion compression (STILL), Gradient Rephasing (GR), Shimadzu Motion Artifact Reduction Technique (SMART).
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• View the DATABASE results for 'Gradient Motion Rephasing' (2).Open this link in a new window

 
Further Reading:
  Basics:
Motion Compensation in MR Imaging
   by ccn.ucla.edu    
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Magnitude Contrast AngiographyMRI Resource Directory:
 - MRA -
 
A type of MRA used to display slow flow across a large volume with a good resolution. Two data volumes are measured; the flow-rephased images show bright signal, the flow-dephased image show dark flow, whereby in both data volumes the signal of the stationary tissue looks the same. The data volumes are subtracted and the signal intensity of flowing blood remains.
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MRI Resources 
Pathology - Resources - Quality Advice - Pacemaker - MRI Physics - Intraoperative MRI
 
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