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12 Cards in this Set
- Front
- Back
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Advantage of TOF |
short acquisition time sensitive to slow flow Reduced sensitivity to intra voxel dephasing |
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Disadvantages of TOF |
Influenced by T1 effects and can confuse hemorrhages and vessels Flow within plan of field of view may be saturated Only see enhancement to incoming flow or very fast flow |
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Advantages of Phase contrast |
Sensitive to flow and velocity Multidirectional flow Lower intra-voxel dephasing background suppression can view fold over direction |
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Disasvantages of Phase contrast |
Longer scan times sensitive to turbulence |
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Parameters for TOF MRA |
TR 45ms TE short FA 60 |
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What is even echo rephasing? |
Flowing nuclei are out of phase at 1st echo and are in phase at 2nd echo. |
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Speed of venous flow |
10cm/s |
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Speed of arterial flow |
80cm/s |
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Laminar flow |
constant |
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spiral flow |
spiral motion |
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vortex flow |
stars as laminar but as it moves through centre of vessels speeds up at walls and spirals |
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turbulent flow |
velocity of flow fluctuates |
