CT appearance of hepatic tumors after microwave coagulation therapy.

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Abstract
The purpose of this study was to evaluate the changes in treated lesions and surrounding parenchyma of the liver as well as associated findings on CT in patients who underwent microwave coagulation therapy for hepatic tumors. We retrospectively reviewed the findings on helical dynamic CT scans obtained before and after percutaneous or intraoperative microwave coagulation therapy for 74 lesions in 63 patients with hepatocellular carcinoma or metastatic hepatic tumors. Indications for microwave coagulation therapy included primary hepatic tumors in 54 patients and hepatic metastasis in nine patients. Sixty percent nonionic contrast material, infused at 3 ml/sec, was followed by sequential arterial phase, portal venous phase, and equilibrium phase helical CT of the entire liver in all patients. All lesions were hypodense and extended to the liver capsule. The lesions treated with percutaneous microwave coagulation therapy were teardrop-shaped, whereas those treated with intraoperative microwave coagulation therapy were round. Peripheral enhancement was seen on contrast-enhanced CT in 93% of the treated lesions immediately after microwave coagulation therapy; however, such enhancement disappeared on follow-up CT. Hemorrhage within the lesions and pleural effusion were found in nine patients. Complications detected on CT included intratumoral abscess (n = 4), subcapsular hematoma (n = 2), tumor dissemination (n = 3), ascites (n = 5), and portal vein thrombosis (n = 1). CT of the liver in patients undergoing microwave coagulation therapy showed findings that were dependent on the technique of therapy. Thus, CT scans must be carefully analyzed to avoid confusing results of therapy with findings that indicate complications requiring further treatment.