King's College London

Background: Conventional bright-blood late gadolinium enhancement (LGE) cardiac magnetic resonance imaging (MRI) often suffers from poor scar-to-blood contrast due to the bright blood pool adjacent to the enhanced scar tissue. Recently, a dark-blood LGE method was developed which increases scar-to-blood contrast without using additional magnetization preparation. Purpose: We aim to histopathologically validate this dark-blood LGE method in a porcine animal model with induced myocardial infarction (MI). Study Type: Prospective. Animal Model: Thirteen female Yorkshire pigs. Field Strength/Sequence: 1.5 T, two-dimensional phase-sensitive inversion-recovery radiofrequency-spoiled turbo field-echo. Assessment: MI was experimentally induced by transient coronary artery occlusion. At 1-week and 7-week post-infarction, in-vivo cardiac MRI was performed including conventional bright-blood and novel dark-blood LGE. Following the second MRI examination, the animals were sacrificed, and histopathology was obtained. Matching LGE slices and histopathology samples were selected based on anatomical landmarks. Independent observers, while blinded to other data, manually delineated the endocardial, epicardial, and infarct borders on either LGE images or histopathology samples. The percentage of infarcted left-ventricular myocardium was calculated for both LGE methods on a per-slice basis, and compared with histopathology as reference standard. Contrast-to-noise ratios were calculated for both LGE methods at 1-week and 7-week post-infarction. Statistical Tests: Pearson's correlation coefficient and paired-sample t-tests were used. Significance was set at P < 0.05. Results: A combined total of 24 matched LGE and histopathology slices were available for histopathological validation. Dark-blood LGE demonstrated a high level of agreement compared to histopathology with no significant bias (−0.03%, P = 0.75). In contrast, bright-blood LGE showed a significant bias of −1.57% (P = 0.03) with larger 95% limits of agreement than dark-blood LGE. Image analysis demonstrated significantly higher scar-to-blood contrast for dark-blood LGE compared to bright-blood LGE, at both 1-week and 7-weeks post-infarction. Data Conclusion: Dark-blood LGE without additional magnetization preparation provides superior visualization and quantification of ischemic scar compared to the current in vivo reference standard. Level of Evidence: 1. Technical Efficacy Stage: 2.