title: Evaluation of rat heart microvasculature with high-spatial-resolution susceptibility-weighted MR imaging.
abstract: OBJECTIVE
  To demonstrate that strandlike hypointense signals seen in the myocardium of normal rat hearts correspond to myocardial microvessels with high-spatial-resolution susceptibility-weighted (SW) magnetic resonance (MR) imaging without injection of contrast medium.
  
  
  METHODS
  Animal experiments were performed with institutional animal care committee approval. Ex vivo cardiac MR imaging was performed in 10 normal Wistar rats with a 4.7-T imager and a cryogenic probe. The hypothesis that thin tubular hypointense signals in the myocardium of rat hearts at SW MR imaging sequences (group 1, n = 6; in-plane resolution, 39 μm) represent intramyocardial microvessels was tested. A superparamagnetic intravascular contrast agent (ferumoxsil; Lumirem) was used to explore the distribution of the intramyocardial microvessels (group 2, n = 4; three-dimensional fast imaging with steady-state free precession sequences). Nonparametric Mann-Whitney tests were performed to compare groups 1 and 2 both for microvascular densities (MVD) on histologic sections and for MR imaging signal intensities (SIs). Wilcoxon signed rank tests were used for paired comparison of subepicardial and subendocardial MVD and SI within groups.
  
  
  RESULTS
  Ferumoxsil opacified the coronary microvasculature (group 2) on MR-matched histologic sections. No statistically significant difference was found between groups 1 and 2 for either MVD or MR imaging SI expressed as ratios between subendocardium and subepicardium (P = .40 and P = .46, respectively). The comparison of mean subendocardial and subepicardial SI within groups revealed significantly more microvessels in the subepicardium with MR (group 1: P = .01; group 2: P = .004).
  
  
  CONCLUSIONS
  Myocardial microvessels appear as strandlike structures on high-spatial-resolution SW MR images without the aid of contrast medium injection.
authors.affiliation: Paris Cardiovascular Research Center, INSERM U970, Université Paris Descartes, Sorbonne Paris Cité, 56 rue Leblanc, 75015 Paris, France; Biostatistics and Epidemiology Unit, Assistance Publique-Hôpitaux de Paris, Hôtel-Dieu, Université Paris Descartes,Paris, France.
authors.forename: Eléonore
authors.initials: E
authors.lastname: Blondiaux
authors.forename: Laetitia
authors.initials: L
authors.lastname: Pidial
authors.forename: José
authors.initials: J
authors.lastname: Vilar
authors.forename: Gwennhael
authors.initials: G
authors.lastname: Autret
authors.forename: Daniel
authors.initials: D
authors.lastname: Balvay
authors.forename: Etienne
authors.initials: E
authors.lastname: Audureau
authors.forename: Patrick
authors.initials: P
authors.lastname: Bruneval
authors.forename: Alain
authors.initials: A
authors.lastname: Bel
authors.forename: Charles-André
authors.initials: CA
authors.lastname: Cuenod
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Silvestre
authors.forename: Olivier
authors.initials: O
authors.lastname: Clément
mesh_terms: D000465:Algorithms; D000818:Animals; D003331:Coronary Vessels / Q000033:anatomy & histology*; D005260:Female; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008833:Microcirculation; D055806:Microvessels / Q000033:anatomy & histology*; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity