Modified quadruple inversion recovery prepulse for arterial spin labeling angiography without the need of subtraction

Introduction Arterial Spin Labeling (ASL) is a well-known technique that allows the non-invasive acquisition of angiograms without the need of a contrast agent [1][2]. ASL angiography is still clinically underused because of several challenges [3]: ASL requires two acquisitions (labeled and non labeled dataset) thereby doubling scan time. The need of subtraction increases the sensitivity to spatial misregistration and the need of the choice of an optimal inversion delay for best blood-to-background contrast introduces some “operator dependence”. An alternative technique not requiring image subtraction has been proposed (Figure 1) [4]. This approach is based on a double inversion (DIR-ASL) prepulse and provides good background suppression if the surrounding tissues have similar T1 values (Figure 1). However, DIR-ASL has only one optimal inversion delay and thus there is a trade-off between background suppression and visualized vessel extent. Our goal was to develop an ASL technique with improved background suppression and without the need of subtraction.