title: Respiratory self-gating for free-breathing abdominal phase-contrast blood flow measurements.
abstract: OBJECTIVE
  To demonstrate the feasibility of using a free-breathing (FB) respiratory self-gated (RSG) approach for abdominal phase-contrast (PC) blood flow measurements.
  
  
  METHODS
  PC-magnetic resonance imaging (MRI) flow measurements were performed within the right renal artery, common hepatic artery, and main portal vein during breath-hold (BH) and FB with both signal averaging and RSG in eight healthy volunteers. The resultant images were qualitatively scored by two independent reviewers blinded to acquisition techniques. Blood flow volume and cross-sectional vessel size measurements were compared for three techniques.
  
  
  RESULTS
  The overall efficiency for the RSG-PC sequence was 38.9% +/- 4.7%. Images acquired with RSG effectively mitigated respiratory motion artifacts, which were clearly evident within FB signal-averaged images. RSG produced similar image quality to that of BH techniques (P > 0.146) and resulted in similar vessel size measurements (P = 0.694). Flow results for both FB RSG and signal-averaged reconstructions correlated well with BH flow measurements (r = 0.97 and 0.92, P < 0.001). However, only the RSG methods demonstrated excellent absolute agreement with BH-PC flow measurements (P = 0.600), with signal-averaged methods resulting in significant overestimations.
  
  
  CONCLUSIONS
  RSG methods can limit respiratory motion artifacts to reduce flow measurement inaccuracies during free-breathing PC measurements in the abdomen.
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Chicago, Illinois, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Jin
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lewandowski
authors.forename: Reed A
authors.initials: RA
authors.lastname: Omary
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Larson
mesh_terms: D000005:Abdomen / Q000098:blood supply*; D000465:Algorithms; D001783:Blood Flow Velocity / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*