title: 3D time-resolved MR angiography (MRA) of the carotid arteries with time-resolved imaging with stochastic trajectories: comparison with 3D contrast-enhanced Bolus-Chase MRA and 3D time-of-flight MRA.
abstract: OBJECTIVE
  Time-resolved MR angiography (MRA) offers the combined advantage of large anatomic coverage and hemodynamic flow information. We applied parallel imaging and time-resolved imaging with stochastic trajectories (TWIST), which uses a spiral trajectory to undersample k-space, to perform time-resolved MRA of the extracranial internal carotid arteries and compare it to time-of-flight (TOF) and high-resolution contrast-enhanced (HR) MRA.
  
  
  METHODS
  A retrospective review of 31 patients who underwent carotid MRA at 1.5T using TOF, time-resolved and HR MRA was performed. Images were evaluated for the presence and degree of ICA stenosis, reader confidence, and number of pure arterial frames attained with the TWIST technique.
  
  
  RESULTS
  With a consensus interpretation of all sequences as the reference standard, accuracy for identifying stenosis was 90.3% for TWIST MRA, compared with 96.0% and 88.7% for HR MRA and TOF MRA, respectively. HR MRA was significantly more accurate than the other techniques (P < .05). TWIST MRA yielded datasets with high in-plane spatial resolution and distinct arterial and venous phases. It provided dynamic information not otherwise available. Mean diagnostic confidence was satisfactory or greater for TWIST in all patients.
  
  
  CONCLUSIONS
  The TWIST technique consistently obtained pure arterial phase images while providing dynamic information. It is rapid, uses a low dose of contrast, and may be useful in specific circumstances, such as in the acute stroke setting. However, it does not yet have spatial resolution comparable with standard contrast-enhanced MRA.
authors.affiliation: Department of Radiology, NYU Langone Medical Center, New York, NY, USA. ruth.lim@nyumc.org
authors.forename: R P
authors.initials: RP
authors.lastname: Lim
authors.forename: M
authors.initials: M
authors.lastname: Shapiro
authors.forename: E Y
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authors.lastname: Wang
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authors.lastname: Law
authors.forename: J S
authors.initials: JS
authors.lastname: Babb
authors.forename: L E
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authors.lastname: Rueff
authors.forename: J S
authors.initials: JS
authors.lastname: Jacob
authors.forename: S
authors.initials: S
authors.lastname: Kim
authors.forename: R H
authors.initials: RH
authors.lastname: Carson
authors.forename: T P
authors.initials: TP
authors.lastname: Mulholland
authors.forename: G
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authors.lastname: Laub
authors.forename: E M
authors.initials: EM
authors.lastname: Hecht