Non-Contrast-Enhanced 4D Intracranial MR Angiography: Optimizations Using a Variable Flip Angle Approach

Peter Schmitt¹, Peter Speier¹, Xiaoming Bi², Peter Weale², Edgar Mueller¹

A novel concept is presented to optimize a FAIR-type spin-labeling technique for non-contrast-enhanced 4D intracranial MR angiography, which is based on an ECG-triggered CINE-like b-SSFP acquisition of multiple 3D phases after selective and non-selective inversion, respectively. Based on numerical Bloch simulations and a volunteer study, it is shown that a variable flip angle scheme, with the flip angle continuously increasing from lower to higher values, results in a significantly longer persistence of the spin labeling. This in turn leads to an improved visualization of late-filling vasculature if compared to the standard approach with constant flip angle.