MR Angiography Flashcards
What are the two ways to study MR Angiography (MRA)?
Time-of-Flight (TOF) and Contrast enhanced
What does Time of Flight Angiography do?
exploits Entry Slice Phenomenon, pre saturates the tissues and doesn’t require IV contrast
Saturation of venous flow allows _ visualization (MRA)
arterial
Saturation of arterial flow allows _ visualization (MRV)
venous
What is the Entry Slice Phenomenon?
when fluid with unsaturated spins flows in the observed slices. These spins will emit a strong signal because of their unsaturated status (flow related enhancement)
The number of slices affected depends on:
flow velocity, slice thickness, and direction of the flow
What is used in 2D ToF Angiography?
Fast GRE sequence (short TR, very short TE, and small to medium flip angles) and saturation pulse that is place to show only venous or arterial imaging
What happens in a contrast enhanced MRA?
Timing is done with timing bolus or care-bolus (visual start); pre and post contrast 3D gradient echo images are taken (short TE and TR to saturate tissues)
What are the differences between ToF and Contrast enhanced MRA?
ToF: does not need contrast, slower, requires the body part to stay stationary for awhile (5-8 minutes), lower SNR & resolution
CE: faster, better resoltuion & SNR, but needs an IV, cannot be repeated, and timing is critical
What are the ways that MR Venography is done?
ToF, Phase contrast (PC), with contrast (late phase), and subtraction of pre and post contrast enhanced images
What is Dynamic MRA?
Start scan then inject; imaging can be done fast (3 sec) then we can see the entrance of blood and its motion in arteries and then to venous washout; The peripheral k-space is done only once and then gets added to the center ones later (post-processing)
In dynamic MRA, adding the peripheral k points later gives good/high _.
resolution
