1. Magnetic resonance angiography
(MRA)

2. Magnetic resonance angiography
(MRA)
 is a group of techniques based on magnetic
resonance imaging (MRI) to image blood
vessels.
 This MRI technique presenting soft tissue
contrast between blood vessels and
surrounding tissues primarily dependent on
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.

3. Magnetic resonance angiography
(MRA)
 The three main types of MRA:
 Time of flight angiography (TOF).
 Phase contrast angiography (PCA).
 Contrast enhanced magnetic resonance
angiography (CE-MRA).

4. Magnetic resonance angiography
(MRA)
 Time of flight angiography (TOF).
 Is a gradient echo sequences with short TR, acquired
with slices perpendicular to the direction of blood
flow.
 Source of diverse flow effects is the difference
between the unsaturated and presaturated spins
and creates a bright vascular image without the
invasive use of contrast media.
 Flowing blood moves unsaturated spins from
outside the slice into the imaging plane.

5. Magnetic resonance angiography
(MRA)
 Time of flight angiography (TOF).
 These completely relaxed spins have full equilibrium
magnetization and produce a much higher signal
than stationary spins if a gradient echo sequence is
generated.
 Performing a presaturation slab on one side parallel
to the slice can selectively destroy the MR signal
from the in-flowing blood from this side of the slice.
 For maximum flow signal, a complete new part of
blood has to enter the slice every repetition (TR)
period, which makes time of flight angiography
sensitive to flow-velocity.

6. Magnetic resonance angiography
(MRA)

9. Magnetic resonance angiography
(MRA)
 Phase contrast angiography (PCA).
 This method images of the blood flow-velocity
are produced.
 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.
 complete suppression of stationary tissue (no
velocity - no signal).

10. Magnetic resonance angiography
(MRA)
 Phase contrast angiography (PCA).
 Phase sensitization can only be
acquired along one axis at a time.
 Phase contrast angiographic techniques
tend to be 4 times slower than TOF
techniques with the same matrix.

11. Magnetic resonance angiography
(MRA)

12. Magnetic resonance angiography
(MRA)
 Contrast enhanced magnetic resonance
angiography (CE-MRA).
 Is based on the T1 values of blood, the
surrounding tissue, and paramagnetic contrast
agent.
 T1-shortening contrast agents reduces the T1
value of the blood (approximately to 50
msec, shorter than that of the surrounding
tissues) and allow the visualization of blood
vessels, as the images are no longer dependent
primarily on the inflow effect of the blood.

13. Magnetic resonance angiography
(MRA)
 Contrast enhanced magnetic resonance
angiography (CE-MRA).
 Contrast enhanced MRA is performed with
 A short TR to have low signal (due to the
longer T1) from the stationary tissue.
 Short scan time to facilitate breath hold
imaging.
 Short TE to minimize T2* effects.
 A bolus injection of a sufficient dose of a
gadolinium chelate.

14. THANKS FOR ALL.