PULSE SEQUENCE STRATEGIES FOR VASCULAR CONTRAST IN TIME-OF-FLIGHT CAROTID MR-ANGIOGRAPHY

A systematic evaluation in healthy volunteers of the relative efficacy of various techniques for background suppression to improve two-dimen sional (2D) and three-dimensional (3D) time-of-flight magnetic resonan ce angiography of the cervical carotid arteries was performed. Convent ional 2D and 3D FISP (fast imaging with steady-state precession) seque nces with flow compensation were compared with modifications of these sequences, including a tracking saturation pulse (2D), prolonged absol ute TEs for fat suppression based on T2 decay (2D and 3D), frequency- selective saturation of fat (2D and 3D), in-plane spatial saturation ( 2D), and magnetization transfer contrast (2D and 3D). The tracking sat uration pulse and slight overlap of the excitation sections provided u niform background suppression without impairing depiction of the morph ology of the cervical carotid arteries. Frequency-selective fat satura tion was the most effective background suppression scheme among the 2D and 3D techniques but was occasionally compromised by local field inh omogeneities. Magnetization transfer contrast provided little suppress ion of stationary tissues in the neck because of the intrinsic limitat ions of the coil. In-plane spatial saturation yielded the highest back ground suppression but reduced apparent arterial diameters and could n ot be implemented in a 3D version. The T2 decay method not only reduc ed the apparent size of the vessels but also their signal intensity.