title: Determination of optimal gadolinium concentration using SSFP for catheter-directed contrast-enhanced coronary MR angiography.
abstract: OBJECTIVE
  To determine the optimal gadolinium concentration for catheter-directed coronary magnetic resonance angiography (MRA) using magnetization-prepared steady-state free-precession (SSFP) in swine.
  
  
  METHODS
  In six pigs, we performed real-time MR imaging-guided coronary artery catheterization using a 1.5 T MR scanner. For catheter-directed coronary MRA, we injected 3-4 mL of dilute Gd at 1 mL/second for each tested concentration (4%, 8%, 10%, and 12% Gd). Eleven images per concentration were acquired using electrocardiographic-triggered, magnetization-prepared two-dimensional (2D) projection SSFP. We compared mean relative signal-to-noise ratio (SNR) values for each concentration using two-way analysis of variance.
  
  
  RESULTS
  The targeted coronary artery was catheterized under real-time MR guidance in all pigs. Magnetization-prepared 2D projection SSFP successfully depicted the coronary arteries in all 44 injections. Mean relative SNR (+/- standard error) was 7.2 +/- 0.49 for 4%, 8.8 +/- 0.47 for 8%, 9.5 +/- 0.38 for 10%, and 8.8 +/- 0.41 for 12%. Injections of 4% dilute gadolinium yielded significantly less relative SNR than the other tested concentrations (P < .05). There were no statistically significant differences between the remaining concentrations.
  
  
  CONCLUSIONS
  For catheter-directed contrast-enhanced coronary MRA, the ideal gadolinium concentration should maximize relative SNR and limit the total gadolinium dose. Using these criteria, of those concentrations we tested in the swine model, 8% injected gadolinium was superior for catheter-directed SSFP coronary MRA.
authors.affiliation: Department of Radiology, Northwestern University, Suite 700, 448 East Ontario St., Chicago, IL 60611, USA. b-schirf@med.northwestern.edu
authors.forename: Brian E
authors.initials: BE
authors.lastname: Schirf
authors.forename: Jordin D
authors.initials: JD
authors.lastname: Green
authors.forename: Kent
authors.initials: K
authors.lastname: Sato
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Larson
authors.forename: Ali
authors.initials: A
authors.lastname: Shaibani
authors.forename: Riad
authors.initials: R
authors.lastname: Salem
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
authors.forename: Reed A
authors.initials: RA
authors.lastname: Omary
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D006328:Cardiac Catheterization; D003287:Contrast Media / Q000008:administration & dosage*; D017023:Coronary Angiography / Q000379:methods*; D019786:Gadolinium DTPA / Q000008:administration & dosage*; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography; D013552:Swine
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA