title: Characterization of viable and nonviable myocardium at MR imaging: comparison of gadolinium-based extracellular and blood pool contrast materials versus manganese-based contrast materials in a rat myocardial infarction model.
abstract: OBJECTIVE
  To determine the contrast agent behavior of gadolinium-based (extracellular and albumin-binding) and manganese-based contrast media for late-enhancement imaging of myocardial infarction.
  
  
  METHODS
  Coronary ligation was performed in 30 rats, and they were serially imaged with segmented inversion-recovery gradient-echo magnetic resonance (MR) imaging (repetition time msec/echo time msec/inversion time msec [fixed], 5.2/2.5/430; flip angle, 15 degrees ) during 1 hour after administration of contrast media by using a 1.5-T MR unit. Serial measurements of the longitudinal relaxation were performed by using the Look-Locker approach (repetition time msec/echo time msec, 1,000/3.5; flip angle, 10 degrees ). Detection and size of infarction were evaluated at each time point and compared with end-point histologic findings.
  
  
  RESULTS
  For all manganese-based media, the contrast agent cleared from the blood pool rapidly. Manganese-based contrast media allowed precise labeling of viable cardiomyocytes within 30 minutes, and the labeling persisted for at least 1 hour. Accumulation of gadoversetamide in the infarct area was apparent after 5 minutes, and the peak contrast-to-noise ratio (CNR) between infarct and myocardium was comparable to the peak CNR of manganese-based contrast agents. Extracellular gadopentetate dimeglumine provided excellent infarct detection but a small imaging window for precise sizing of the infarct if a fixed inversion time of 430 msec was used. Albumin-binding gadolinium-based contrast media provided a longer imaging window, but infarct size was overestimated because of the nonspecific distribution of the unbound gadolinium agent.
  
  
  CONCLUSIONS
  When extracellular gadolinium-based agents are used for infarct size measurement, imaging parameters and timing are important because the kinetics of both normal and irreversibly injured myocardium must be considered. Manganese-based agents are highly specific and less sensitive to timing for infarct size determination, but further studies are required to determine if they are feasible for human use.
authors.affiliation: Center for Cardiovascular Magnetic Resonance, Department of Medicine, Cardiovascular Division, Washington University Medical School, St Louis, MO, USA. flacke@uni-bonn.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Flacke
authors.forename: John S
authors.initials: JS
authors.lastname: Allen
authors.forename: Jon M
authors.initials: JM
authors.lastname: Chia
authors.forename: James H
authors.initials: JH
authors.lastname: Wible
authors.forename: M Peri
authors.initials: MP
authors.lastname: Periasamy
authors.forename: Max D
authors.initials: MD
authors.lastname: Adams
authors.forename: I Kofi
authors.initials: IK
authors.lastname: Adzamli
authors.forename: Christine H
authors.initials: CH
authors.lastname: Lorenz
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003287:Contrast Media / Q000493:pharmacokinetics*; D004195:Disease Models, Animal; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D017895:Manganese Compounds / Q000493:pharmacokinetics*; D009203:Myocardial Infarction / Q000175:diagnosis*; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003287:Contrast Media; D017895:Manganese Compounds; D009942:Organometallic Compounds; C112666:gadoversetamide