Jalal jalal shokouhi – MD General secretary of Iranian society of radiology President of Iranian radiologists cooperative 17th -18th December 2010, Shahid beheshti university, Tehran, Iran
MRA ○ Black Spine echo. ○ White TOF Phase contrast Contrast enhanced Motion related MRA ○ TOF ○ Phase contrast
TOF Continuous excitation non moving tissue saturation and loosing signal increased moving blood signal: 2D: high velocity blood 3D : high and low velocity blood
TOF Advantages: 5min (short time) Slow flow sensitivity Reduced sensitivity to intra-voxel dephasing Disadvantage : Sensitive to T1 effects (methemoglubin) Saturation in phase flow Enhancement is limited in flow entry, very high flow
2D TOF – MRI Advantages: Large area of coverage Sensitive to slow flow Sensitive to T1 effects (methemoglubin) Disadvantage: Low resolution Saturation of in-phase flow Ventetian artifact (respiratory and patient motion) Tissue in and out of the slice
3D TOF-MRI Advantages: High resolution for small vessels Sensitive to T1 effects (Met.) Disadvantages: Saturation in-plane flow Small area coverage 4D flow sensitized in 3T and 7T High vessel to tissue contrast High spatial resolution( mm lenticulostriate vessels) High SNR
MRA image reformations: 1. MIP 2. SSD
MRA summary Techniques Phenomenon MRA, TOF, PC DSA Flow Sensitive Sensitive +- Anatomy ++ Hemodynamic ++++ Doppler effect +- Conclusion MRA = DSA + Color doppler
indications in intracranial TOF 3D>2D, 4D>3D indications in neck vessels TOF 3D>2D + PC 3D + CE+++ > TOF and PC +