| Part Ⅰ:Early MR Manifestation of Small Hepatocellular Carcinoma after Radiofrequency AblationOBJECTIVE:To assess the MR features and patterns of small hepatocellular carcinoma (HCC) in the early follow-up period (within 1 month) after radiofrequency ablation (RFA).MATERIALS AND METHODS:A total of 35 patients with 40 HBV-related small HCCs who underwent complete RFA were included in our study. MR features (including apparent diffusion coefficient (ADC) values) before and after RFA were observed and compared.RESULTS:During the immediate follow-up within 24 hours after RFA, lesions demonstrated marked hyperintensity in nonenhanced T1-weighted images, with some displaying a target appearance with an iso-hypointense central zone (n=17); while at the 1-month follow-up, most lesions showed a target appearance (n=32) with the size of the entire ablative zone decreased. In T2-weighted images, tumors were typically iso-hypointense with a surrounding hyperintense band within 24 hours of RFA (n=33); after 1 month,8 lesions displayed relative hyperintensity. In contrast-enhanced images, the periablative area displayed continuous or discontinuous rim enhancement in most cases. In diffusion weighted imaging (DWI), most ablated lesions were hypo- or isointense (n=31) within 24 hours of RFA; while after 1 month, a large proportion of tumors became globally (n=21) or peripherally (n=7) hyperintense. ADC values showed an up-and-down evolution as a whole within the 1-month follow-up, significant differences existed between ADC values within 24 hours and at 1 month after RFA (P=0.040).CONCLUSION:MR features of small HCC after RFA had certain characteristics. they reflected the pathological evolution of tumor necrosis, assisted in treatment and complication assessment. Thus, a regular follow-up is of great value.Part Ⅱ:Clinical and Early Imaging Risk Factors of Intrahepatic Distant Recurrence after Radiofrequency Ablation for Small Hepatocellular CarcinomaOBJECTIVE:To determine both clinical and imaging risk factors of intrahepatic distant recurrence (IDR) after complete radiofrequency ablation (RFA) for HBV-related small hepatocellular carcinoma (HCC).MATERIALS AND METHODS:A total of 35 patients with 40 HBV-related small HCCs who underwent complete RFA were included in our study. Univariate analysis by the Kaplan-Meier method and log-rank test, and multivariate analysis by a stepwise Cox hazard model were used to assess the incidence and potential clinical and MR imaging risk factors for IDR. Additionally, receiver operating characteristic (ROC) analysis and corresponding area under the curve (AUC) statistics were used for discriminatory accuracy of apparent diffusion coefficient (ADC) values in terms of IDR prediction.RESULTS:The median follow-up period was 25 (4-45) months, IDR was observed in 20 (57.1%) patients. The 12- and 24-month cumulative IDR-free survival rates were 76.7% and 61.3%. Univariate analysis revealed that pretreatment albumin< 3.5 g/dl (P=0.026), multinodular tumor (P=0.032), ablative margin< 3 mm (P=0.0074), no or disrupted periablational enhancement within 24 hours (P=0.001) and at 1 month (P=0.043) after RFA as well as T1-hyperintensity of the central ablative zone at 1 month after RFA (P=0.004) were related to IDR. Multivariate analysis revealed that pretreatment albumin< 3.5 g/dl (P=0.032), multinodular tumor (P=0.012), no or disrupted periablational enhancement within 24 hours of RFA (P=0.001) and T1-hyperintensity of the central ablative zone at 1 month after RFA (P=0.003) were independent risk factors for IDR. During the 1-month follow-up, ADC showed an up-and-down evolution without significant value in predicting IDR after RFA.CONCLUSION:IDR occurred more in HBV patients with low serum albumin. multiple nodules, and those who have lesions with no or disrupted periablational enhancement and persistent hyperintensity in the central ablative zone in T1-weighted images within the 1-month follow-up after RFA, these patients should take a closer surveillance to monitor for IDR. |
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