title: Accuracy of cardiac magnetic resonance of absolute myocardial blood flow with a high-field system: comparison with conventional field strength.
abstract: OBJECTIVE
  The aim of this study was to determine the accuracy of cardiac magnetic resonance (CMR) first pass (FP) perfusion measures of absolute myocardial blood flow (MBF) with a 3.0-T magnet and compare these measures with FP perfusion at 1.5-T with absolute MBF by labeled microspheres as the gold standard.
  
  
  BACKGROUND
  First-pass magnetic resonance (MR) myocardial perfusion imaging can quantify MBF, but images are of low signal at conventional magnetic field strength due to the need for rapid acquisition.
  
  
  METHODS
  A pig model was used to alter MBF in a coronary artery during FP CMR (intracoronary adenosine followed by ischemia). This produces an active zone with a range of MBF and a control zone. Microspheres were injected into the left atrium with concurrent reference sampling. FP MR perfusion imaging was performed at 1.5-T (n = 9) or 3.0-T (n = 8) with a saturation-recovery gradient echo sequence in short-axis slices during a bolus injection of 0.025 mmol/kg gadolinium-diethylenetriamine pentaacetic acid. Fermi function deconvolution was performed on active and control region of interest from short-axis slices with an arterial input function derived from the left ventricular cavity. These MR values of MBF were matched to microsphere values obtained from short-axis slices at pathology.
  
  
  RESULTS
  Occlusion MBF was 0.21 +/- 0.26 ml/min/g, adenosine MBF was 2.28 +/- 0.99 ml/min/g, and control zone MBF was 0.70 +/- 0.22 ml/min/g. The correlation of MR FP CMR with microsphere was close for both field strengths: 3.0-T, r = 0.98, p < 0.0001 and 1.5-T, r = 0.95, p < 0.0001. The 95% confidence limits of agreement were slightly narrower at 3.0-T (3.0-T = 0.49 ml/min/g, 1.5-T = 0.68 ml/min/g, p < 0.05). The FP CMR image characteristics were better at 3.0-T (noise and contrast enhancement were both superior at 3.0-T). In myocardial zones where MBF <0.50 ml/min/g, the correlation with microspheres was closer at 3.0-T (r = 0.55 at 1.5-T, r = 0.85 at 3.0-T).
  
  
  CONCLUSIONS
  Absolute MBF by FP perfusion imaging is accurate at both 1.5- and 3.0-T. Signal quality is better at 3.0-T, which might confer a benefit for estimating MBF in ischemic zones.
authors.affiliation: University of Vermont College of Medicine, Burlington, Vermont, USA. timothy.christian@uvm.edu
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Christian
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Bell
authors.forename: Lawrence
authors.initials: L
authors.lastname: Whitesell
authors.forename: Michael
authors.initials: M
authors.lastname: Jerosch-Herold
mesh_terms: D000241:Adenosine; D000818:Animals; D003287:Contrast Media; D003326:Coronary Circulation; D004195:Disease Models, Animal; D019786:Gadolinium DTPA; D006940:Hyperemia / Q000139:chemically induced / Q000175:diagnosis* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008863:Microspheres; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013552:Swine; D013997:Time Factors
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA; D000241:Adenosine