Abstract 197: Quantification of Absolute Myocardial Blood Flow With Contrast Enhanced MRI Approaching a Pixel Resolution: Validation vs. Microspheres
Introduction: Myocardial blood flow (MBF) can be estimated from gadolinium enhanced first pass perfusion MR imaging. We hypothesized that MBF can be quantified at approximately the pixel level from MR perfusion images. Results were validated with microspheres.
Methods: Local hyperemia of MBF was induced in 7 dogs through intracoronary adenosine infusion. A dual-bolus contrast technique with steady-state free precession imaging was used to acquire first-pass perfusion MR images (1.5 Tesla). Fluorescent microspheres were the reference standard for absolute MBF (in ml/g/min) on 16 sectors (8 endocardial and 8 epicardial) of a mid ventricular slice. MR time intensity curves were analyzed on a pixel-by-pixel basis and converted to parametric maps using model constrained deconvolution.
Results: Figure-1⇓ shows a colorized MR perfusion pixel map with corresponding microsphere MBF on the same absolute color scale. Average MBF from microspheres were 5.1±1.5 ml/g/min in hyperemic sectors and 1.3±0.7 ml/g/min in control zones. Transmural estimates of MBF from MR matched well with microspheres (y=0.75x-0.50, r=0.89). For subsector comparison, both endocardial sectors (y=0.80x-0.41, r=0.91) and epicardial sectors (y=0.70x-0.63, r=0.85) showed good correlations of MBF between MR and microspheres. Bland Altman analysis showed no significant bias in all comparisons. Qualitatively, color perfusion maps were comparable to microsphere bull’s-eye plots in all animals.
Conclusion: Myocardial blood flow can be quantified at approximately the pixel level on MR perfusion images. These methods could improve the objectivity of diagnosing coronary artery disease in patients.