CT Spectrum of Transient Peritumoral Hyperemia after Radiofrequency Thermal Ablation of Hepatic Tumors

ABSTRACT

PURPOSE: To determine the incidence and pattern of peritumoral hyperemia at CT after radiofrequency thermal ablation of hepatic tumors, as well as its correlation with local marginal recurrence. MATERIALS AND METHODS: Forty-five tumor nodules in 28 patients with hepatocellular carcinoma (n=34) or metastasis (n=11) were treated by RF thermal ablation. Serial follow-up contrast- enhanced CT scans were reviewed by three radiologists for 1) the presence, 2) the morphological characteristics [circumferential, THAD (transient hepatic attenuation difference), nodular form], and 3) the temporal course (acute, persistent, delayed onset pattern) of peritumoral hyperemia after RF thermal ablation. These findings were correlated with the frequency of recurrence at the margin of the treated tumors. RESULTS: The frequency of acute hyperemia observed on immediate follow-up CT scans after RF ablation was 71% (32/45). There was the local recurrence in nine of 32 tumors (28%) with hyperemia and in one of 13 (8%) without hyperemia (p>0.05). Among 32 tumors, the circumferential form was observed in 22 (69%); the THAD form in eight (25%); and the nodular form in two (6%). Marginal recurrence was noted in five of 22 tumors circumferential tumors (23%), in three of eight (38%) with the THAD form, and in one of two (50%) which were nodular. Among 32 nodules, an acute transient pattern was noted in 21 (66%), a persistent pattern in nine (28%), and a nodular pattern in two (6%). There was marginal recurrence in two (10%) of 21 tumors with acute transient hyperemia, in six (67%) of nine with persistent hyperemia, and in both tumors with delayed-onset hyperemia. There was significant correlation between the pattern of persistent/delayed-onset hyperemia and marginal tumor recurrence of (p=0.001). CONCLUSION: Although peritumoral hyperemia after RF thermal ablation therapy is a frequent transient finding at follow-up imaging studies, its temporal pattern may help detect early marginal tumor recurrence.