Pattern and chronological change of iodized oil retention in radiofrequency ablation-induced vascular injury area: differentiation from iodized oil retention in recurrent hepatocellular carcinoma on computed tomography.

PURPOSE: The purpose of this study was to evaluate the pattern and the chronological change of iodized oil retention in a radiofrequency ablation (RFA)-induced vascular injury area as compared with that in recurrent hepatocellular carcinoma (HCC).

MATERIALS AND METHODS: Informed consents from all the patients and approval from the institutional review board were obtained. The computed tomographic scans of 226 patients who underwent both RFA and subsequent transcatheter arterial chemoembolization for recurrence were retrospectively reviewed. The RFA-induced vascular injury area that did not have HCC recurrence in it were examined and assessed whether iodized oil was retained after transcatheter arterial chemoembolization. We evaluated the incidence, the shape, and the duration of the iodized oil retention in the RFA-induced vascular injury area and compared them with those found in recurrent HCC from the same patient. The rate of misinterpretation was calculated.

RESULTS: Of 59 RFA-induced vascular injury areas that were within the range of segmental embolization, 33 RFA-induced vascular injury areas (55.9%) in 31 patients retained iodized oil. The shapes of the iodized oil in the RFA-induced vascular injury area were diffuse-dense (n = 13), diffuse-faint (n = 8), nodular-dense (n = 8), or nodular-faint (n = 4). In 29 (93.5%) of 31 patients, at least one recurrent HCC retained iodized oil, and they were all nodular-dense in shape. The duration of the retention in RFA-induced vascular injury area (mean [SD], 3.3 [3.2] months) was significantly shorter than that in recurrent tumors (21.2 [12.5] months, P < 0.001). In 21.2% (7/33) of the cases, the iodized oil density in the RFA-induced vascular injury area was clinically misinterpreted as recurrent HCC.

CONCLUSIONS: The RFA-induced vascular injury area frequently retains iodized oil, which could mimic recurrent HCC. However, we determined that iodized oil in the RFA-induced vascular injury area differs from that in HCC in variety in shape and shorter duration of retention.