TOF PET - This PET technology means that the time difference between two photons detected as a coincidence will be used to estimate the actual place of positron annihilation.
TOF MRA - This Magnetic Resonance angiography technique means that a sequence with small time of repetition TR will be used to saturate the stationary nucleus, while the flowing nucleus with Time-Of-Flight will be maximal.
Both techniques produce beautiful images:
More information on TOF-PET:
More information on TOF-MRA: