Microwave ablation of hepatic tumors with a third generation system: loco­regional efficacy in a prospective cohort study with intermediate term follow-up.

PURPOSE: To evaluate the safety and intermediate-term efficacy of percutaneous microwave ablation (MWA) in primary and secondary liver tumors using a third generation MWA device, under ultrasound guidance. PATIENTS AND METHODS: Sixty-two patients (median age 74 years, 73 % males) with 69 liver tumors were enrolled in this prospective observational study. Forty-seven patients (76 %) had hepatocellular carcinoma (HCC) and 15 (24 %) metastases. Median follow-up was 3.6 years. RESULTS: Median tumor diameter at contrast enhanced computed tomography was 23 mm (I-III quartiles, 18 - 31 mm). All procedures were performed percutaneously using a 2.45 GHz generator. Median ablation time was 10 minutes (I-III quartiles, 10 - 14 minutes). A single percutaneous antenna insertion was performed for 56/69 (81 %) of the tumors. Technical success was obtained in all tumors. Primary efficacy at 24 hours was achieved in 68/69 (99 %) tumors. The overall one-year cumulative local tumor progression rate was 15.1 % (95 % CI, 7.7 - 24.8 %) with no significant difference between HCC and metastases (p = 0.26). There was one procedure-related mortality (1.6 %) and one major bleeding (1.6 %). CONCLUSION: Microwave ablation is a valid option for thermal ablation of HCC and liver metastases with comparable complication rate to other local ablative procedures.

Contrast enhanced ultrasound: Roles in immediate post-procedural and 24-h evaluation of the effectiveness of thermal ablation of liver tumors.

PURPOSE: To retrospectively assess the diagnostic accuracy of immediate post-procedural CEUS, 24-h CEUS, and 24-h CT in verifying the effectiveness of thermal ablation of liver tumors ablation, using the combined results of 3-month post-procedure CEUS and MDCT as the reference standard. MATERIALS AND METHODS: From our database, we selected patients who had immediate post-procedural CEUS and 24-h CEUS and MDCT examinations after undergoing thermal ablation of a liver tumor between January 2009 and March 2010. The study population consisted of 53 subjects and 55 tumors (44 HCC and 11 metastasis) were evaluated. Thirty-seven tumors were treated with radiofrequency and 18 with microwave ablation. Post-procedural CEUS, 24-h CEUS and MDCT, and 3-month follow-up CEUS and MDCT images were blindly reviewed by two radiologists, who measured the size of the ablation area on the post-procedural and 24-h studies. They also evaluated the ability of each of these three index tests to predict the outcome (residual tumor vs. no residual tumor) using imaging studies done at the 3-month follow-up as the reference standard. RESULTS: Mean tumor diameter on preablation CEUS (the day before treatment) was 20 ± 9 mm. Mean diameter of the necrotic area was 29 ± 9 mm on post-procedural CEUS, 34 ± 11 mm on 24-h CEUS, and 36 ± 11 mm on 24-h MDCT. Diameters of the necrotic area (mean and maximum) on post-procedural CEUS were significantly smaller than those measured on 24-h CEUS or 24-h MDCT, which were not significantly different. For predicting the presence of residual tumor at the 3-month follow-up, post-procedural CEUS, 24-h CEUS, and 24-h MDCT displayed sensitivity of 33%, 33%, and 42%; specificity of 92%, 97%, and 97%; negative predictive value of 84%, 85%, and 83%. The accuracy parameters of these three imaging modalities were not significantly different from one another. CONCLUSIONS: In patients undergoing thermal ablation for liver tumors, the immediate post-procedural CEUS seems comparable to 24-h CEUS and MDCT in terms of detecting residual disease.

Contrast-enhanced ultrasound in planning thermal ablation of liver metastases: Should the hypervascular halo be included in the ablation volume?().

INTRODUCTION: Liver metastases often exhibit a hypervascular halo during the arterial phase of contrast-enhanced ultrasonography (CEUS). This finding has no correlates on baseline gray-scale imaging, and it has never been characterized. The aim of this study was to identify the features of this halo and determine whether it should be included in the ablation volume during thermal ablation procedures. MATERIALS AND METHODS: We prospectively enrolled 25 patients referred to our department for thermal ablation of liver metastases. Before treatment all patients underwent CEUS, and the maximum diameter of the metastatic lesion was measured before administration of the ultrasound contrast agent and during the arterial and portal venous phases of the contrast contrast-enhanced study. Maximum diameters in the different vascular phases were compared with the Turkey-Kramer test. Two biopsies were obtained from each lesion with a 21-gauge needle: 1) one from the center of the metastasis to confirm the diagnosis and 2) one from the hypervascular peripheral halo identified in the arterial phase at CEUS. RESULTS: The mean (±standard deviation) maximum lesion diameter was 2.67 ± 1.2 cm before contrast agent injection, 3.50 ± 1.4 cm during the arterial phase, and 2.71 ± 1.2 cm during the venous phase. The difference between maximum diameters measured before contrast enhancement and in the arterial phase was highly significant (mean: 0.84 ± 0.45 cm, p < 0.0001). Histological examination of halo specimens revealed inflammatory infiltrates with no evidence of tumor infiltration in 24/25 (96%) cases and normal hepatic parenchymal tissue in the 25th specimen. DISCUSSION: The hypervascular halo surrounding liver metastases during the arterial phase of CEUS represents a chronic inflammatory infiltrate, not tumor infiltration. However, since chronic inflammation appears to promote neovascularization and the production of tumoral growth factors, it seems wise to include the hypervascular halo in the intended-to-treat volume when planning the ablation procedure.

Hepatocellular carcinoma treated with radiofrequency ablation: comparison of pulse inversion contrast-enhanced harmonic sonography, contrast-enhanced power Doppler sonography, and helical CT.

OBJECTIVE: The purpose of this study was to compare the efficacy of contrast-enhanced pulse inversion harmonic imaging with contrast-enhanced power Doppler sonography and helical CT to determine incomplete local treatment after radiofrequency ablation in patients with hepatocellular carcinoma. MATERIALS AND METHODS: Thirty-five consecutive patients (24 men and 11 women; mean age, 64 years) with 43 hepatocellular carcinomas (3.6 +/- 1.1 cm) were treated using internally cooled radiofrequency ablation therapy. Therapeutic response was evaluated at 4 months with dual-phase contrast-enhanced helical CT, conventional power Doppler Sonography, and pulse inversion harmonic imaging using a sonographic contrast agent (SH-508). CT and sonographic studies were reviewed separately in random order by four radiologists at different consensus conferences. Sensitivity and specificity of the sonographic methods were determined using CT as a gold standard and results were compared using the McNemar test. RESULTS: CT examinations identified residual tumor in 12 lesions (27.9%). Although conventional contrast-enhanced power Doppler sonography identified residual viable tumor foci in four incompletely treated lesions (9.3%), contrast-enhanced pulse inversion harmonic imaging identified residual tumoral enhancement in 10 lesions (23.3%). Thus, the sensitivity of pulse inversion harmonic imaging (83.3%) was significantly greater (p < 0.05) for detecting residual nonablated tumor compared with conventional contrast-enhanced power Doppler sonography. CONCLUSION: Our study suggests that contrast-enhanced pulse inversion harmonic imaging may enable the detection of residual nonablated tumor in more cases than contrast-enhanced power Doppler sonography and may ultimately prove to be a useful adjunct for percutaneous ablation therapies. Nevertheless, contrast-enhanced axial imaging (CT or MR imaging) is currently the most sensitive test for managing thermal ablation for patients with hepatocellular carcinoma.