Corey Alexander Couto MD, Presenter: Nothing to Disclose

Bettina Siewert MD, Abstract Co-Author: Nothing to Disclose

Maryellen Ruth Morris Sun MD, Abstract Co-Author: Investigator, Bracco Group

Vassilios D. Raptopoulos MD, Abstract Co-Author: Nothing to Disclose

Robert G. Sheiman MD, Abstract Co-Author: Nothing to Disclose

To evaluate CT/MRI imaging appearance following RFA of hepatocellular carcinoma (HCC), and correlate findings with pathology of explanted livers.

This is an IRB approved, HIPAA-compliant retrospective study. We performed a database search for patients who had undergone RFA for HCC followed by liver transplant. The following imaging features were assessed: target (treated) lesion enhancement; number, size, location and shape of hyperenhancement following RFA; distance from RFA site. Interobserver variability was calculated. Explant liver pathology was correlated with imaging findings.

51 patients (44 male, 7 female, mean 57.48 years; range 40-72) with 58 lesions were included. Average imaging follow-up was 9 months (range 1-36 months) at 1-3 month intervals. 57 of 58 RFA sites demonstrated an enhancing rim; all resolved on follow-up imaging. 89 THAD/THIDs were observed in 55 of 58 (94.8%) of patients on immediate CT scan following RFA. 56 were wedge-shaped, 28 geographic and 5 linear. 55 of 89 were in the same segment as the tumor, 34 were in a remote segment. Interobserver agreement for the presence of THAD/THIDs and their characterization was high (kappa=0.80). Of wedge-shaped and geographic foci, 51% decreased in size, 39% resolved and 10% remained stable. Of 16 nodular foci, 8 remained stable, 3 resolved, 3 increased in size and 2 decreased in size. Tumor was present at pathology in 31 cases. 23 occurred at the site of RFA (13 with nodular enhancing correlate, 10 without). 8 occurred in nodular enhancing lesions distinct from the RFA site, either showing deenhancement on portal venous imaging (n=3) or isoenhancement on the portal venous phase (n=5). Thus, of the nodular arterially enhancing lesions that were isodense on portalvenous phase, 5 (38%) represented tumor on pathology and 8 (62%) THAD/THIDs.

THAD/THIDs are present in almost all patients immediately following percutaneous RFA of HCC and only 10% of those remain stable. 38% of these are seen in a different segment than that containing the RFA site. Over 1/3rd of nodular arterially enhancing lesions distant from the RFA site which became isodense on portal venous phase proved to be recurrence of HCC.

Nodular arterially enhancing lesions distant from the RFA site and isodense on portal venous phase represent recurrent HCC in 38% and THAD/THIDs in 62%. Close interval follow-up is advised.

Couto, C, Siewert, B, Sun, M, Raptopoulos, V, Sheiman, R, CT and MRI Imaging Findings Following RFA for Hepatocellular Carcinoma: Correlation with Pathology Following Liver Transplant.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11015464.html