Coronary angiogenesis: Detection in vivo with MR imaging sensitive to collateral neocirculation - Preliminary study in pigs

PURPOSE: To assess the ability to track neovascularization over time with a magnetic resonance (MR) imaging technique sensitized to new intramyocardia l collateral development as a means of evaluating therapeutic angiogenesis. MATERIALS AND METHODS: Magnetization preparation plus spatial frequency reo rdering was applied to-distinguish new intramyocardial collateral vessels f rom normal circulation on the basis of geometric differences. A vascular oc cluder was inserted in 34 pigs, and they were assigned randomly to treatmen t groups with either placebo or angiogenic growth factor. Collateral extent determined with collateral-sensitive MR imaging was correlated with direct measurements by means of three-dimensional (3D) computed tomography (CT), coronary blood flow distribution determined with microspheres, and findings at histologic examination. Changes in the signal at collateral-sensitive M R imaging before and after treatment were assessed by two observers blinded to treatment. RESULTS: The collateral extent determined with collateral-sensitive MR imag ing correlated well with findings at 3D CT (r = 0.95) and with microspheres (r = 0.86). Furthermore, the collateral extent determined with collateral- sensitive MR imaging increased significantly (P < .001) in response to the administration of an angiogenic growth factor but not to placebo. The corre spondence of findings at collateral-sensitive MR imaging to collateral neov ascularization was confirmed at histologic examination. CONCLUSION: The presence of intramyocardial collateral microvessels was acc urately determined with collateral-sensitive MR imaging. The technique may be useful in clinical studies of therapeutic angiogenesis.