TOF MRA

Time-of-flight magnetic resonance angiography: A MRI technique for imaging flow within blood vessels and, consequently, the anatomy of blood vessels without the use fo contrasting agent.  It is based on the principle of repeated application of magnetic pulses followed by a recording of signals emitted by protons as they “relax” out of the state induced by the magnetic pulse.  Since blood flowing within vessels in the field being imaged brings fresh protons to area the summation of recordings after repeated magnetic stimulation shows the increasing volume of signal due fresh protons within the blood as oppose to the lower signal summation in surrounding tissue where fresh protons are not being introduced between magnetic pulses.