Let’s TWIST again: Temporal and Spatial High-Resolution 3D MR-Angiography of the Hand

Compared to conventional contrastenhanced MR angiography (MRA), which provides a spatial high-resolution threedimensional (3D) MRA data set of the vascular target region, MRA with TWIST (time-resolved angiography with stochastic trajectories) with its high temporal resolution offers an additional dynamic component. It presents a broad range of advantages for all vascular diagnostic questions where blood flow dynamics play a role. For example, an angiographic 3D display with high temporal resolution is a prerequisite for evaluating arterio-venous malformation (AVM), as well as venous malformations (DVM) in the brain, aortic dissections or vascular shunts. Data acquisition with the syngo TWIST sequence creates a series of high-resolution 3D MRA data sets that together contain this dynamic information. Additionally, the acquisition of multiple measurements in rapid succession renders the aspect of contrast agent timing less critical. For the reasons indicated above, syngo TWIST examinations are gaining in clinical relevance. From a technical perspective, one challenge to this examination is the relatively high storage capacity required for data acquisition and subsequent reconstruction, whereby data reconstruction of all dynamic 3D MRA data sets requires several minutes. From a medical perspective, the challenge lies in the relatively large number of images to be acquired and diagnosed. For this reason, the data to be reconstructed (source images, subtractions, maximum intensity projections (MIP), etc.) should be clarified beforehand with the physician. In the following, we report on the use of time-resolved TWIST-MRA of the hand and present a possible examination sequence. We begin, however, by taking a brief look at the theory behind TWIST data acquisition.