Semi-automatic detection of myocardial trabeculation using cardiovascular magnetic resonance: correlation with histology and reproducibility in a mouse model of non-compaction

Background

The definition of left ventricular (LV) non-compaction is controversial, and discriminating between normal and excessive LV trabeculation remains challenging. Our goal was to quantify LV trabeculation on cardiovascular magnetic resonance (CMR) images in a genetic mouse model of non-compaction using a dedicated semi-automatic software package and to compare our results to the histology used as a gold standard.

Methods

Adult mice with ventricular non-compaction were generated by conditional trabecular deletion of Nkx2–5. Thirteen mice (5 controls, 8 Nkx2–5 mutants) were included in the study. Cine CMR series were acquired in the mid LV short axis plane (resolution 0.086?×?0.086x1mm³) (11.75 T). In a sub set of 6 mice, 5 to 7 cine CMR were acquired in LV short axis to cover the whole LV with a lower resolution (0.172?×?0.172x1mm3). We used semi-automatic software to quantify the compacted mass (M_c), the trabeculated mass (M_t) and the percentage of trabeculation (M_t/M_c) on all cine acquisitions_. After CMR all hearts were sliced along the short axis and stained with eosin, and histological LV contouring was performed manually, blinded from the CMR results, and M_t, M_c and M_t/M_c were quantified. Intra and interobserver reproducibility was evaluated by computing the intra class correlation coefficient (ICC).

Results

Whole heart acquisition showed no statistical significant difference between trabeculation measured at the basal, midventricular and apical parts of the LV. On the mid-LV cine CMR slice, the median M_t was 0.92 mg (range 0.07–2.56 mg), M_c was 12.24 mg (9.58–17.51 mg), M_t/M_c was 6.74% (0.66–17.33%). There was a strong correlation between CMR and the histology for M_t, M_c and M_t/ M_c with respectively: r²?=?0.94 (p?<?0.001), r²?=?0.91 (p?<?0.001), r²?=?0.83 (p?<?0.001). Intra- and interobserver reproducibility was 0.97 and 0.8 for M_t; 0.98 and 0.97 for M_c; 0.96 and 0.72 for M_t/M_c, respectively and significantly more trabeculation was observed in the M_c Mutant mice than the controls.

Conclusion

The proposed semi-automatic quantification software is accurate in comparison to the histology and reproducible in evaluating M_c, M_t and M_t/ M_c on cine CMR.