Fast three-dimensional time-of-flight MR angiography of the intra-cranial vasculature.

Magnetic resonance angiography is most commonly performed with the three-dimensional (3D) time-of-flight (TOF) technique. As currently practiced, this requires long image acquisition times (5-10 minutes). The authors show that the acquisition time of 3D TOF images can be reduced to less than 1 minute by using a very short TR (<10 msec). Under normal flow conditions, the major vessels of the circle of Willis were consistently well demonstrated on these fast 3D TOF images. Signal saturation was observed in studies of patients with abnormal blood flow. In those cases, it was demonstrated that serial acquisition of fast 3D TOF data during and after contrast agent administration could be used to overcome the saturation effects. Time-resolved fast 3D TOF imaging during and after contrast agent administration can also provide qualitative assessment of flow and may depict other features that cannot be observed in TOF studies with long imaging times.