Inter-study reproducibility of cardiovascular magnetic resonance myocardial feature tracking

Background: Cardiovascular magnetic resonance myocardial feature tracking (CMR-FT) is a recently described method of post processing routine cine acquisitions which aims to provide quantitative measurements of circumferentially and radially directed ventricular wall strain. Inter-study reproducibility is important for serial assessments however has not been defined for CMR-FT. Methods: 16 healthy volunteers were imaged 3 times within a single day. The first examination was performed at 0900 after fasting and was immediately followed by the second. The third, non-fasting scan, was performed at 1400. CMR-FT measures of segmental and global strain parameters were calculated. Left ventricular (LV) circumferential and radial strain were determined in the short axis orientation (Ecc_SAX and Err _SAX respectively). LV and right ventricular longitudinal strain and LV radial strain were determined from the 4-chamber orientation (Ell _LV, Ell_RV, and Err_LAX respectively). LV volumes and function were also analysed. Inter-study reproducibility and study sample sizes required to demonstrate 5% changes in absolute strain were determined by comparison of the first and second exams. The third exam was used to determine whether diurnal variation affected reproducibility. Results: CMR-FT strain analysis inter-study reproducibility was variable. Global strain assessment was more reproducible than segmental analysis. Overall Ecc_SAX was the most reproducible measure of strain: coefficient of variation (CV) 38% and 20.3% and intraclass correlation coefficient (ICC) 0.68 (0.55-0.78) and 0.7 (0.32-0.89) for segmental and global analysis respectively. The least reproducible segmental measure was EllRV: CV 60% and ICC 0.56 (0.41-0.69) whilst the least reproducible global measure was Err_LAX: CV 33.3% and ICC 0.44 (00.77). Variable reproducibility was also reflected in the calculated sample sizes, which ranged from 11 (global Ecc_SAX) to 156 subjects (segmental Ell_RV). The reproducibility of LV volumes and function was excellent. There was no diurnal variation in global strain or LV volumetric measurements. Conclusions: Inter-study reproducibility of CMR-FT varied between different parameters, as summarized above and was better for global rather than segmental analysis. It was not measurably affected by diurnal variation. CMR-FT may have potential for quantitative wall motion analysis with applications in patient management and clinical trials. However, inter-study reproducibility was relatively poor for segmental and long axis analyses of strain, which have yet to be validated, and may benefit from further development.