The intra-observer reproducibility of cardiovascular magnetic resonance myocardial feature tracking strain assessment is independent of field strength.

Background: Cardiovascular magnetic resonance myocardial feature tracking (CMR-FT) is a promising novel method for quantification of myocardial wall mechanics from standard steady-state free precession (SSFP) images. We sought to determine whether magnetic field strength affects the intra-observer reproducibility of CMR-FT strain analysis.

Methods: We studied 2 groups, each consisting of 10 healthy subjects, at 1.5 T or 3T Analysis was performed at baseline and after 4 weeks using dedicated CMR-FT prototype software (Tomtec, Germany) to analyze standard SSFP cine images. Right ventricular (RV) and left ventricular (LV) longitudinal strain (Ell(RV) and Ell(LV)) and LV long-axis radial strain (Err(LAX)) were derived from the 4-chamber cine, and LV short-axis circumferential and radial strains (Ecc(SAX), Err(SAX)) from the short-axis orientation. Strain parameters were assessed together with LV ejection fraction (EF) and volumes. Intra-observer reproducibility was determined by comparing the first and the second analysis in both groups.

Results: In all volunteers resting strain parameters were successfully derived from the SSFP images. There was no difference in strain parameters, volumes and EF between field strengths (p>0.05). In general Ecc(SAX) was the most reproducible strain parameter as determined by the coefficient of variation (CV) at 1.5 T (CV 13.3% and 46% global and segmental respectively) and 3T (CV 17.2% and 31.1% global and segmental respectively). The least reproducible parameter was Ell(RV) (CV 1.5 T 28.7% and 53.2%; 3T 43.5% and 63.3% global and segmental respectively).

Conclusions: CMR-FT results are similar with reasonable intra-observer reproducibility in different groups of volunteers at 1.5 T and 3T. CMR-FT is a promising novel technique and our data indicate that results might be transferable between field strengths. However there is a considerable amount of segmental variability indicating that further refinements are needed before CMR-FT can be fully established in clinical routine for quantitative assessment of wall mechanics and strain.