Quantification of myocardial scar of different etiology using dark- and bright-blood late gadolinium enhancement cardiovascular magnetic resonance

Abstract

Dark-blood late gadolinium enhancement (LGE) has been shown to improve the visualization and quantification of areas of ischemic scar compared to standard bright-blood LGE. Recently, the performance of various semi-automated quantification methods has been evaluated for the assessment of infarct size using both dark-blood LGE and conventional bright-blood LGE with histopathology as a reference standard. However, the impact of this sequence on different quantification strategies in vivo remains uncertain. In this study, various semi-automated scar quantification methods were evaluated for a range of different ischemic and non-ischemic pathologies encountered in clinical practice. A total of 62 patients referred for clinical cardiovascular magnetic resonance (CMR) were retrospectively included. All patients had a confirmed diagnosis of either ischemic heart disease (IHD; n = 21), dilated/non-ischemic cardiomyopathy (NICM; n = 21), or hypertrophic cardiomyopathy (HCM; n = 20) and underwent CMR on a 1.5 T scanner including both bright- and dark-blood LGE using a standard PSIR sequence. Both methods used identical sequence settings as per clinical protocol, apart from the inversion time parameter, which was set differently. All short-axis LGE images with scar were manually segmented for epicardial and endocardial borders. The extent of LGE was then measured visually by manual signal thresholding, and semi-automatically by signal thresholding using the standard deviation (SD) and the full width at half maximum (FWHM) methods. For all quantification methods in the IHD group, except the 6 SD method, dark-blood LGE detected significantly more enhancement compared to bright-blood LGE (p < 0.05 for all methods). For both bright-blood and dark-blood LGE, the 6 SD method correlated best with manual thresholding (16.9% vs. 17.1% and 20.1% vs. 20.4%, respectively). For the NICM group, no significant differences between LGE methods were found. For bright-blood LGE, the 5 SD method agreed best with manual thresholding (9.3% vs. 11.0%), while for dark-blood LGE the 4 SD method agreed best (12.6% vs. 11.5%). Similarly, for the HCM group no significant differences between LGE methods were found. For bright-blood LGE, the 6 SD method agreed best with manual thresholding (10.9% vs. 12.2%), while for dark-blood LGE the 5 SD method agreed best (13.2% vs. 11.5%). Semi-automated LGE quantification using dark-blood LGE images is feasible in both patients with ischemic and non-ischemic scar patterns. Given the advantage in detecting scar in patients with ischemic heart disease and no disadvantage in patients with non-ischemic scar, dark-blood LGE can be readily and widely adopted into clinical practice without compromising on quantification.

Figure 1

Schematic overview of two semi-automated signal intensity thresholding methods, with the standard deviation (SD) method in the top panel and the full width at half maximum (FWHM) method in the bottom panel.

Figure 2

Manual and semi-automated scar quantification in a case of ischemic heart disease (IHD, top rows), dilated/non-ischemic heart disease (NICM, middle rows), and hypertrophic cardiomyopathy (HCM, lower rows) using both conventional bright-blood LGE (left panel) and dark-blood LGE (right panel). The cyan number in each image indicates the % of enhanced left ventricular myocardium for the given method. SD, standard deviation; FWHM, full width at half maximum.

Figure 3

Graphical presentation of the mean percentages of enhanced left ventricular myocardium for the ischemic heart disease (IHD), dilated/non-ischemic cardiomyopathy (NICM), and hypertrophic cardiomyopathy (HCM) groups as assessed by the various quantification methods for both conventional bright-blood LGE (left panel) and dark-blood LGE (right panel). The error bars indicate the standard error of the mean.

Figure 4

Graphical presentation of the mean differences in percentage of enhanced left ventricular myocardium between dark-blood LGE and conventional bright-blood LGE as assessed by the various quantification methods in the ischemic heart disease (IHD), dilated/non-ischemic heart disease (NICM), and hypertrophic cardiomyopathy (HCM) groups. The error bars indicate the standard error of the mean. The asterisks indicate a statistically significant difference. SD, standard deviation, FWHM, full width at half maximum.