title: MRI evaluation of microvascular obstruction in experimental reperfused acute myocardial infarction using a T1 and T2 preparation pulse sequence.
abstract: OBJECTIVE
  To investigate a T1 and T2 preparation pulse sequence to evaluate microvascular obstruction (MO) in a porcine model of reperfused acute myocardial infarction (AMI).
  
  
  METHODS
  A total of 14 pigs with reperfused AMI underwent MRI examinations at baseline and three to four hours after reperfusion. MRI scans included a left ventricular functional study, T1 and T2 measurement on a 1.5T MRI system. At reperfusion, first-pass myocardial perfusion (FPMP) images were obtained after bolus injection of gadopentetate dimeglumine followed by an intravenous drip. Delayed contrast-enhanced MRI (DE-MRI) and T1 measurements were performed 30 and 45 minutes, respectively, after the bolus, during a constant infusion of gadopentetate dimeglumine.
  
  
  RESULTS
  In 11 pigs MO was hypoenhanced in FPMP and DE-MRI. In later T1 preparation difference images postcontrast, MO was hyperenhanced while delayed hyperenhanced (DHE) regions appeared dark. MO areas on DE-MRI and T1 images were comparable. T1 reduction (%) postcontrast in MO was small compared to measurements from DHE regions (P < 0.0001) and similar to those from control segments (P = 0.66). Precontrast T1 and T2 values at reperfusion from MO and DHE regions were larger than in control regions.
  
  
  CONCLUSIONS
  Using T1 preparation under a constant gadopentetate dimeglumine (Gd-DTPA) infusion, delayed imaging at 30 to 45 minutes demonstrates MO as a positive contrast with larger T1 values. Elevated T1 and T2 values in MO precontrast may also help to differentiate them from both control and DHE regions.
authors.affiliation: Imaging Research, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada. ysyang@sri.utoronto.ca
authors.forename: Yuesong
authors.initials: Y
authors.lastname: Yang
authors.forename: Warren D
authors.initials: WD
authors.lastname: Foltz
authors.forename: John J
authors.initials: JJ
authors.lastname: Graham
authors.forename: Jay S
authors.initials: JS
authors.lastname: Detsky
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Dick
authors.forename: Graham A
authors.initials: GA
authors.lastname: Wright
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D023921:Coronary Stenosis / Q000503:physiopathology*; D004195:Disease Models, Animal; D019786:Gadolinium DTPA / Q000008:administration & dosage; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008833:Microcirculation / Q000503:physiopathology; D009203:Myocardial Infarction / Q000503:physiopathology*; D015425:Myocardial Reperfusion; D013552:Swine; D013997:Time Factors
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA