Additional value of CMR parametric mapping in tissue characterization of common benign pediatric cardiac tumors.

BACKGROUND: Cardiac Magnetic Resonance (CMR) parametric mapping is underexplored in cardiac tumors.

OBJECTIVES: To evaluate the contribution of mapping sequences on the characterization of pediatric tumors.

METHODS: All pediatric patients referred for cardiac tumors at Bambino Gesù Children's Hospital from June 2017 to November 2023, who underwent CMR with mapping sequences, were included. The diagnosis of tumor type was performed according to signal characteristics on different sequences. Mass parametric mapping for each subtype and interobserver variability was assessed.

RESULTS: Sixteen patients were enrolled. The mean age at CMR was 7 ± 5 years. "Traditional" mass-type assessment diagnosed hemangioma (Group A) in 3 patients (19%), fibroma (Group B) in 4 patients (25%), rhabdomyoma (Group C) in 6 patients (37%), and lipoma (Group D) in 3 patients (19%). The ANOVA analysis revealed significant differences in mass native T1 and mass extracellular volume (ECV) values among the four subgroups (p<0.001 for both comparisons). The mean native T1 and ECV values were respectively 1465 ± 158 msec and 54 ± 4% for Group A, 860 ± 118 msec and 93 ± 4% for Group B, 1007 ± 57 msec and 23 ± 5% for Group C, and 215 ± 13 msec and 0 ± 0% for Group D.

CONCLUSIONS: Mass mapping analysis is feasible and reproducible in children. ECV values provide the most accurate differentiation. Mass ECV consistently resembles normal myocardium in rhabdomyoma, is extremely high (approaching 100%) in fibroma, equals to zero in lipoma, and matches blood pool ECV (1-Hct) in hemangioma.