The prelims comprise: TOF MRA is a helpful technique to explore the intracranial and extracranial vasculature identifying the anatomy and common pathologies. 3mm is the practical size cutoff point, beneath sensitivity of TOF MRA decrease for the detection of intracranial aneurysms. A common problem with TOF MRA is the loss of signal in high-grade stenoses, providing no landmarks for its measurement. The distal cervical internal carotid artery just below the skull base and the distal cervical vertebral artery are particularly prone to dissection as a result of blunt trauma. Interpretation of TOF MRV requires careful analysis of source images and conventional sequences in order to reduce diagnostic errors.