OPTIMIZING 3-DIMENSIONAL TIME-OF-FLIGHT MR-ANGIOGRAPHY WITH VARIABLE REPETITION TIME

PURPOSE: To implement and evaluate a variable repetition time (TR) mod ification of three-dimensional (3D) time-of-flight (TOF) magnetic reso nance (MR) angiography. MATERIALS AND METHODS: Variable- and constant- TR 3D TOF MR angiography of the intracranial vasculature was performed in 20 healthy volunteers and 10 patients with known or suspected cere brovascular disease. Total acquisition time was short and held constan t for all studies. Frequency-selective fat saturation (FS) and magneti zation transfer saturation (MTS) pulses were applied. The associated m aximum-intensity projection (MIP) images were evaluated quantitatively for contrast-to-noise (C/N) and qualitatively for depiction of vessel s that exhibit slow flow. RESULTS: Variable-TR MIP images exhibited im proved C/N and depiction of small peripheral vessels and venous struct ures when compared with constant-TR MIP images. These observations wer e consistent for all studies. CONCLUSIONS: The variable-TR modificatio n improved the depiction of intracranial vessels that exhibit slow now .