title: Automated vessel edge detection in velocity-encoded cine-MR (VEC-MR) flow measurements: a retrospective evaluation in critically ill patients.
abstract: OBJECTIVE
  To assess feasibility of automated edge detection in magnetic resonance (MR) flow calculations in a clinical setting with critically ill patients.
  
  
  METHODS
  Velocity encoded cine-MR (VEC-MR) flow measurements cross-sectional area (CSA), mean spatial velocity (MSV), instantaneous flow (IF), flow (F), 0.5 T Philips, TR 800-800, TE=8 ms, 30 degrees flip angle, FOV 280 mm, 128 x 256 matrix, temporal resolution 16 time frames/RR, VENC=120 cm/s) were obtained in 20 major thoracic human vessels (ascending aorta, main, right and left pulmonary artery-AAO, MPA, RPA, LPA) of five patients, suffering from severe chronic thromboembolic pulmonary hypertension (CTEPH). Flow maps were evaluated by two independent observers using conventional manual edge detection (INTER m/m). Flow calculations were performed by one observer using both, manual and automated edge detection (INTRA m/a), by a second observer using automated edge detection two times (INTRA a/a) and by two independent observers using automated edge detection (INTER a/a). Evaluation time was measured. Linear regression analysis and Student's t-test were performed.
  
  
  RESULTS
  Overall regression coefficients (r2) for INTER m/m, INTRA m/a, INTER a/a and INTRA a/a, respectively, were as follows: CSA, 0.91, 0.91, 0.96, 0.98; MSV, 0.97, 0.99, 0.99, 0.99; IF, 0.98, 0.99, 0.99, 0.99; F, 0.98, 0.99, 0.99, 0.99. Manual CSA values differed significantly from automated data in MPA (P=0.01), RPA (P=0.0008) and LPA (P=0.02). No difference was found for the other assessed parameters of the pulmonary circulation. Average evaluation time per vessel was 20.2+/-2.6 min for manual and 2.1+/-0.7 min for automated edge detection (P<0.00001).
  
  
  CONCLUSIONS
  The software program used provided reproducible data, lead to a 90% reduction in evaluation and calculation time and, therefore, might excel the utilization of VEC-MR flow measurements. Despite variations in the evaluation of the pulmonary circulation CSAs, flow assessment is feasible in critically ill patients.
authors.affiliation: Department of Radiology, Ludwig-Boltzmann Institute for Clinical and Experimental Radiology, University of Vienna, Währingergürtel 18-20, A-1090 Vienna, Austria. christine.henk@univie.ac.at
authors.forename: Christine B
authors.initials: CB
authors.lastname: Henk
authors.forename: Stephan
authors.initials: S
authors.lastname: Grampp
authors.forename: Werner
authors.initials: W
authors.lastname: Backfrieder
authors.forename: Jasmin
authors.initials: J
authors.lastname: Liskutin
authors.forename: Christian
authors.initials: C
authors.lastname: Czerny
authors.forename: Gerhard H
authors.initials: GH
authors.lastname: Mostbeck
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D002908:Chronic Disease; D016638:Critical Illness; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis; D016014:Linear Models; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011652:Pulmonary Circulation / Q000502:physiology*; D012189:Retrospective Studies; D013895:Thoracic Arteries / Q000473:pathology*