Shrinkage Rate of Necrotic Lesion after Radiofrequency (RF) Ablation of Hepatocellular Carcinoma: Correlation with Marginal Recurrence and Influencing Factors

PURPOSE: To compare the CT findings of hepatocellular carcinomas (HCCs) immediately after radiofrequency (RF) ablation with those obtained at six months' follow-up, to analyse the relationship between degree of shrinkage of a necrotic lesion and marginal recurrence, and to evaluate the factors influencing shrinkage. MATERIALS AND METHODS: We retrospectively evaluated 54 patients with 62 HCCs who underwent only RF ablation between May 1999 and July 2000. For six months after ablation, all had been free from marginal recurrence ad new-growth tumors. The findings of six-month follow-up CT were compared with those obtained immediately after RF ablation, and the volume of each necrotic lesion was calculated and compared. In terms of degree of shrinkage, tumors were classified as belonging to either group I (below 50%), group II (50-80%) or group III (above 80%). Each tumor was analysed in terms of its Child-Pugh classification, vascularity at CT, size, treatment details, the post-ablation appearance of its margins, and the presence, during necrosis, of peritumoral vessles and air bubbles. For statistical evaluation, Fisher's exact test was used. Shrinkage after ablationwas correlated to marginal recurrence during a period of more than one year. RESULTS: The Follow-up CT at six months showed that since immediately after ablation, necrotic lesions had shrunk by an average of 72%. Peritumoral vessels were seen in 12 of 14 cases in group I (86%), three of 13 in cases of group II (23%), and 11 of 35 in group III (31%)(p=0.001). Immediate CT revealed the presence of air bubbles in two cases in group I (14%), five in group II (38%), and 24 in group III (69%)(p<0.05). At follow-up CT performed during a period of more than one year, marginal recurrence was noted in four cases in group I, two in group II and two in group III (p<0.05). CONCLUSION: When a necrotic lesion contains no peritumoral vessels but does contain air bubbles, the degree of post-RFablation shrinkage increases. The greater the shrinkage, the less the marginal recurrence rate.

MRI Findings of Intracranial Hemangioblastoma

PURPOSE: Complete resection of the tumor nodule(mural nodule or solid portion of the tumor) is the essential goal of surgical treatment for heman-gioblastoma. The purpose of this study was to classify the morphologic types of intracranial hemangioblastoma on MRI and to compare the location and contour of tumor nodule on MRI with those on angiography. MATERIALS AND METHODS: The MRI findings of 34 lesions(38 lesions if 4 spinal cord lesions were included) in 26 patients(17 males and 9 females, range of age, 18-67 years, mean, 39 years) with surgically and histopathologically proved intracranial hemangioblastomas were reviewed. Seventeen patients underwent CT scanning in a short interval. Contrast-enahnced T1 -weighted imaging pa- tterns of hemangioblastoma were classified according to Ho's morphologic types. The location and contour of tumor nodule were compared between MRI and angiography in 15 patients(24 lesions). RESULTS: By location, cerebellar hemisphere was predominated(55%), followed by cerebellar vermis(26%), supratentorial region(5%), and medulla oblongata (3%). Spinal cord lesions(11%) were seen in 3 patients of 5 von HippeI-Lindau diseases. The frequency of morphologic types was as follows; Type 1 (purely cystic), 3%, Type 2(mural nodule), 50%, Type 3(cyst with wall enhancement), 3%, Type 4 (cystic nodule), 15%, Type 5(solid with internal cyst), 9%, and Type 6(solid), 20%. All tumor nodules(33 lesions) enhanced intensely with intravenous contrast material on MRI, of which 24 lesions(in 15 patients) revealed hypervascular masses fed by pial arteries on angiography. They were superficial and abutted pia mater partially or in large portion on both MR I and angiography. CONCLUSION: Over 70% of intracranial hemangioblastomas had a surrounding cyst, and superficial, pial-based location and number of the tumor nodules on MRI was correlated well with those on angiography. MRI is the examination of choice for preoperative evaluation of intracranial hemangioblastoma.