The purpose of this study was to assess Magnetic Resonance Imaging (MRI) patterns of hepatocellular carcinoma (HCC) treated with percutaneous ethanol injection (PEI) or Transarterial Chemoembolization (TACE) and, consequently, the potential role of MR Imaging in the follow-up of these lesions. HCC treated with PEI. Thirty-one patients with a single small HCC lesion underwent MR Imaging at 0.5 T before and after PEI. In all cases before and after treatment contrast enhanced Computed Tomography (CT) and US-guided fine-needle biopsy were performed. Twenty-seven of 31 HCC lesions in which complete tumor necrosis was obtained with PEI showed homogeneous hypointensity on SE T2-weighted MR images. This feature corresponded to an unenhanced and low-attenuation area on follow-up contrast-enhanced CT scans. All these lesions were negative for malignant cells at fine-needle biopsy follow-up. In four HCCs, high-signal areas on SE T2-weighted images and high-attenuation areas on contrast-enhanced CT scans were observed, suggesting the presence of residual tumor tissue; these lesions were positive for malignant cells at 6-month fine-needle biopsy. In each case, incomplete tumor necrosis was confirmed at pathologic examination of the surgical specimen. HCC treated with TACE. Twenty-one patients with a total of 36 HCC lesions underwent plain and Gadolinium-enhanced MR Imaging before and after TACE. 10 HCC lesions were later surgically resected; 26/36 lesions underwent MR, CT and angiographic follow-up. At short-term follow-up exams (15-30 days), hypointensity was present on enhanced SE T1 weighted sequences in those lesions (5/10) in which complete tumor necrosis was histologically confirmed. In the remaining 5/10 HCC lesions, persistent viable tumor portions were found at pathology. These areas corresponded to areas on hyperintensity of Gadolinium-enhanced SE T1-weighted images. Hypointensity on both SE T2-weighted and enhanced SE T1-weighted images was a characteristic pattern on long-term follow-up MR images in 21/26 unresected lesions; this finding was correlated with devascularization at angiography; the presence of hyperintense areas on SE T2 weighted and enhanced SE T1-weighted images corresponded to the persistence of hypervascular (viable) areas at angiography
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