MR digital subtraction angiography with asymmetric echo acquisition and complex subtraction: improved lumen and stenosis visualization

The use of complex subtraction in dynamic thick slab 2D MR digital subtraction angiography (MR-DSA) has been shown to eliminate partial volume effects, which are present if vessels cover a small fraction of the 2D slab. However, spin dephasing still results in a poor visualization of areas with complex flow. In this paper, it is shown that this can be overcome by using asymmetric echo (ASE) acquisition combined with complex subtraction. It is proven that an ASE acquisition does not destroy information necessary for complex subtraction if the subtraction is performed in k-space. As a consequence, the subtraction reconstruction is as reliable as the magnitude reconstruction of a single ASE data set. Experiments with ASE and complex subtraction show that flow voids near stenoses disappear, that the signal-to-noise ratio is improved and that temporal resolution is increased.