Reproducibility of FFR-CT at High Levels of Iterative Reconstruction

Abstract

Introduction: FFR-CT has a developing presence as a non-invasive means of assessing myocardial ischaemia. Reproducibility of workstation-based FFR-CT is crucial, and data in this area are limited, particularly with differing reconstruction algorithms. Iterative reconstruction algorithms are used to lower radiation dose while maintaining image quality. While these techniques are widely applied to CTCA, there are limited data on the accuracy of FFR-CT at high levels of iterative reconstruction. Methods: FFR-CT was retrospectively performed on 20 patients who underwent both CTCA and stress MIBI within 60 days at a single centre between January 2014 and December 2018. Two radiologists independently calculated the FFR at three points along the RCA, LAD and LCx onsite using prototype software (cFFR version 3.1, Siemens GmbH, Forchheim, Germany) on either ADMIRE 4 (n = 11) or SAFIRE 4 (n = 9) i26. Intraclass correlation coefficients (ICC) were calculated using a two-way consistency model.Tabled 1Observer 1 mean FFRObserver 2 mean FFRICC (95% CI)Proximal0.99 (+/− 0.01)0.99 (+/− 0.01)0.82 (0.70–0.89)Mid0.93 (+/− 0.05)0.94 (+/− 0.04)0.94 (0.90–0.97)Distal0.84 (+/− 0.08)0.85 (+/− 0.09)0.93 (0.79–0.92)Total0.92 (+/− 0.04)0.93 (+/− 0.04)0.97 (0.96–0.98) Open table in a new tab Results: 8 patients had lesions in proximal or mid vessels that were thought to be of at least moderate severity on CTCA. Conclusion: Onsite FFR-CT has excellent levels of reproducibility and this is maintained despite high levels of iterative reconstruction. This may allow CTCA to be acquired at lower radiation doses even if CT-FFR is planned.