Agreement between single and multiple ROI strategies for hepatic T1 and ECV mapping in tetralogy of Fallot and Fontan circulation.

PURPOSE: Native T1 and extracellular volume (ECV) mapping have emerged as promising tools for noninvasive assessment of hepatic congestion and fibrosis; however, optimal strategies for region-of-interest (ROI) selection remain uncertain. The aim was to evaluate the level of agreement between two methods for quantifying hepatic native T1 and ECV: single wide ROI versus multiple small ROIs, in patients with repaired tetralogy of Fallot (TOF) and Fontan circulation.

METHODS

This agreement study prospectively enrolled outpatients with repaired TOF or Fontan circulation between 2022 and 2025. All participants underwent hepatic evaluation using a cardiac Magnetic Resonance Imaging (MRI) protocol on a 3.0-T scanner. Native and post-contrast T1 mapping were acquired using Modified Look-Locker Inversion Recovery (MOLLI) sequences. Hepatic T1 and ECV were measured using (1) one wide ROI avoiding vascular structures and (2) three small circular ROIs placed in distinct parenchymal regions. Agreement was assessed using intraclass correlation coefficients (ICC) and survival-agreement plots.

RESULTS

A total of 61 patients was included (31 with TOF; 30 with Fontan circulation). Agreement between single-ROI and multiple-ROI strategies was excellent in TOF patients for both native T1 and ECV (ICC = 0.98), and good in patients with Fontan circulation for both parameters (ICC = 0.79). Survival-agreement analysis demonstrated that in TOF patients, all measurements differed by less than 80 ms for native T1 and less than 5% for ECV. In Fontan patients, 86% of measurements showed differences < 80 ms for native T1 and < 5% for ECV, reflecting greater hepatic heterogeneity while preserving overall concordance between ROI strategies.

CONCLUSIONS

Hepatic native T1 and ECV measurements showed excellent agreement between single-wide and multiple-small ROI strategies in repaired TOF, supporting interchangeable use for longitudinal follow-up. In Fontan patients, concordance between methods was also good, as demonstrated by both ICC and survival-agreement analyses, indicating that either strategy remains feasible; nonetheless, the greater hepatic heterogeneity in this population warrants some caution when comparing measurements obtained with different ROI approaches.