Novel Dynamic Chest Radiography Technique for Assessing Pulmonary Regurgitation in Repaired Tetralogy of Fallot

Background Cardiac MRI plays a key role in the assessment of pulmonary regurgitation (PR) after surgical repair of tetralogy of Fallot (TOF). However, its use may be limited by low availability, claustrophobia, or incompatible pacemakers or defibrillators. Purpose To evaluate the utility of dynamic chest radiography (DCR) for estimating PR after surgical TOF repair. Materials and Methods In this retrospective observational study, patients with repaired TOF who underwent DCR and phase-contrast cardiac MRI within 1 week between February 2018 and June 2024, and age- and sex-matched healthy volunteers, were enrolled. Temporal changes in pixel values of pulmonary arteries on DCR images were analyzed using specialized software. The maximum pixel value change (Max PV), maximum slope of pixel value change (Max PV Slope), and minimum slope of pixel value change (Min PV Slope) during a single cardiac cycle were calculated. Correlation between these indexes and PR fraction (PRF) at phase-contrast MRI and the ability of each index to differentiate severe PR (>30%) from nonsevere PR (≤30%) were assessed. Pearson correlation and receiver operating characteristic analyses were performed. Results The final study sample included 58 patients with repaired TOF (mean age, 30.6 years ± 10.3 [SD]; 29 [50%] male patients) and 14 healthy volunteers (mean age, 31.1 years ± 5.5; eight [57%] male individuals). Compared with patients with nonsevere PR and volunteers, patients with severe PR had the highest mean Max PV (severe PR: 26.2% ± 8.1; nonsevere PR: 14.1% ± 4.2; volunteers: 9.4% ± 3.0; P < .001), highest mean Max PV Slope (percentage change per frame) (severe PR: 6.6 ± 2.2; nonsevere PR: 2.9 ± 0.9; volunteers: 1.8 ± 0.6; P < .001), and lowest mean Min PV Slope (percentage change per frame) (severe PR: -7.2 ± 2.0; nonsevere PR: -4.6 ± 1.6; volunteers: -3.5 ± 1.4; P < .001). For patients with repaired TOF, all indexes were correlated with PRF; of these indexes, Max PV Slope had the highest correlation (R = 0.87; P < .001) and area under the receiver operating characteristic curve (0.98 [95% CI: 0.94, 1.0]; cutoff, 4.13%), yielding a sensitivity of 93% and specificity of 94%. Conclusion Max PV Slope from DCR showed high diagnostic value for PR severity in patients with repaired TOF. © RSNA, 2026 Supplemental material is available for this article. See also the editorial by Gerstner Saucedo in this issue.