James Enos, Robert McCarter and Russell Cross
Journal of Biomedical Imaging and Bioengineering (2018) Volume 2, Issue 1

Background: Real-time cardiac MRI (CMR) has been shown to accurately assess cardiac output during exercise when compared with the clinical gold-standard Fick technique; however, most strategies for exercise stress CMR have involved exercise outside of the MRI scanner with rapid transition into the magnet for imaging, which cannot capture active or peak exercise conditions. Novel re-binning reconstruction of real-time imaging data with robust automated motion correction and improved temporal resolution may be well-suited for CMR during in-scanner exercise. Methods: Real-time acquisitions with conventional and re-binning reconstructions were collected in healthy volunteers at rest and at two exercise workloads during in-scanner exercise using an MRIcompatible cycle ergometer. Bland-Altman analyses and intraclass correlation coefficients compared left ventricular volumes measured by each real-time technique during exercise. Results: Twenty-five volunteers were enrolled - demographics [mean ± SD (range)]: age 23.1 ± 11.2 years (10–59); weight, 65.9 ± 18.9 kg (27.1–109); 72% female. Bland-Altman analyses demonstrated no differences in left ventricular volumes obtained via each technique at rest or during exercise with a maximum mean difference of <6 ml (p ≥ 0.05) during exercise. Intraclass correlation coefficients (ICCs) indicated strong agreement between measurement techniques (all ICCs ≥ 0.85). Conclusions: Assessing left ventricular volumes during exercise using the re-binning technique is feasible and yields similar results in adults and children compared to conventional real-time imaging, which has been shown to correlate with measurement of cardiac output via the gold-standard Fick technique. Important advantages of the re-binning technique include improved temporal resolution and signal-to-noise compared to conventional real-time approaches. The re-binning technique also has the added benefit of presenting reconstructed images as a single cardiac cycle for more efficient cardiac functional assessments using standard clinical post-processing tools.

Cardiac MRI, Exercise, Real-time imaging, Re-binning reconstruction, Left ventricular volume, Pediatric

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