title: Automated segmentation of blood-flow regions in large thoracic arteries using 3D-cine PC-MRI measurements.
abstract: OBJECTIVE
  Quantitative analysis of vascular blood flow, acquired by phase-contrast MRI, requires accurate segmentation of the vessel lumen. In clinical practice, 2D-cine velocity-encoded slices are inspected, and the lumen is segmented manually. However, segmentation of time-resolved volumetric blood-flow measurements is a tedious and time-consuming task requiring automation.
  
  
  METHODS
  Automated segmentation of large thoracic arteries, based solely on the 3D-cine phase-contrast MRI (PC-MRI) blood-flow data, was done. An active surface model, which is fast and topologically stable, was used. The active surface model requires an initial surface, approximating the desired segmentation. A method to generate this surface was developed based on a voxel-wise temporal maximum of blood-flow velocities. The active surface model balances forces, based on the surface structure and image features derived from the blood-flow data. The segmentation results were validated using volunteer studies, including time-resolved 3D and 2D blood-flow data. The segmented surface was intersected with a velocity-encoded PC-MRI slice, resulting in a cross-sectional contour of the lumen. These cross-sections were compared to reference contours that were manually delineated on high-resolution 2D-cine slices.
  
  
  RESULTS
  The automated approach closely approximates the manual blood-flow segmentations, with error distances on the order of the voxel size. The initial surface provides a close approximation of the desired luminal geometry. This improves the convergence time of the active surface and facilitates parametrization.
  
  
  CONCLUSIONS
  An active surface approach for vessel lumen segmentation was developed, suitable for quantitative analysis of 3D-cine PC-MRI blood-flow data. As opposed to prior thresholding and level-set approaches, the active surface model is topologically stable. A method to generate an initial approximate surface was developed, and various features that influence the segmentation model were evaluated. The active surface segmentation results were shown to closely approximate manual segmentations.
authors.affiliation: Eindhoven University of Technology, Den Dolech 2, 5612 AZ, Eindhoven, The Netherlands. r.f.p.v.pelt@tue.nl
authors.forename: Roy
authors.initials: R
authors.lastname: van Pelt
authors.forename: Huy
authors.initials: H
authors.lastname: Nguyen
authors.forename: Bart
authors.initials: B
authors.lastname: ter Haar Romeny
authors.forename: Anna
authors.initials: A
authors.lastname: Vilanova
mesh_terms: D000465:Algorithms; D001331:Automation / Q000379:methods; D001783:Blood Flow Velocity; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D011859:Radiography; D012039:Regional Blood Flow; D013895:Thoracic Arteries / Q000000981:diagnostic imaging* / Q000473:pathology