Time-resolved angiography with interleaved stochastic trajectories (TWIST) is a 3D time-resolved MR angiography (MRA) sequence - being vendor-specific to Siemens.
In comparison to contrast-enhanced MRA techniques that obtain images at a single point in time, time-resolved MRA obtains a series of images over a period of time, tracking the passage of a contrast bolus.
The principle of TWIST lies with special k-space sampling. The center of k-space holds information about image contrast while the periphery of k-space encodes information on edges and details. The TWIST sequence over-samples central k-space relative to peripheral k-space.
Time-resolved MRA is particularly useful clinically in situations where contrast dynamics are important. Examples include assessment of arteriovenous malformations and investigating collateral flow around vessel stenoses 1.
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