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Figure 1 Gadolinium enhancement of a radiofrequency ablation lesion. The time-course (1 to 600 min) after injection of 0.225 mmol/kg gadolinium demonstrates four characteristic phases of enhancement: (A) Schematic of magnetic resonance (MR) images (30-W radiofrequency [RF] and 40-W RF = 30- and 40-W RF ablation lesions; Myo = right ventricular myocardial wall; EP = epicardial side; EN = endocardial side; RV-C = right ventricular cavity). (B) Phase 1 with a contrast void. (C and D) Phase 2 displaying an increasing peripheral enhancement (white arrows). (E) Phase 3 showing "very" delayed enhancement with high signal intensity throughout the ablation lesion. (F) Phase 4 displaying loss of enhancement with decreasing signal intensity and lesion size. (G) Corresponding pathological specimen.