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CEUS performs equally to CT and MRI in the follow-up of patients treated for liver tumors by RFA.

The aim of this study was to evaluate changes of hepatic transit time (HTT) in patients treated by radiofrequency ablation (RFA). Five consecutive patients (2 females, 3 males; mean age 66 years) referred for treatment of liver neoplasm with percutaneous application of RFA were included in this study. The HTT of contrast agent (Sonovue(R); Bracco International B.V., Amsterdam, The Netherlands) was measured in patients with liver metastases on the basis of time intensity curve (TIC(R)) before and after RFA, respectively. Changes of HTT before vs after RFA were compared with therapeutic response based on three-phase dynamic CT or MRI. Before RFA HTT in all 5 patients was less than 10 s (mean 6.2+/-1.5 s). After RFA HTT in patients with complete therapeutic response was 11.3+/-1.2 s, whereas two patients with incomplete treatment showed unchanged HTT below 10 s (mean 6.3+/-1.8 s). Successful RFA leads to a normalization in HTT. HTT using ultrasound contrast agent appears to provide a new and alternative approach in assessing the therapeutic effect of RFA in liver metastases.

In an attempt to increase necrotic zones in liver tissue by radiofrequency ablation fresh bovine liver was coagulated by means of a needle electrode continuously perfused with NaCl solution. Power output (60 W) and application time (15 min) were kept constant while the perfusion was varied in terms of saline concentration (0.9, 5.85 and 10%) and perfusion rate (40 or 80 ml/h). Our results showed that the use of higher osmolar saline solutions in radiofrequency ablation with perfused needle electrodes did not lead to significantly larger coagulation volumes. By contrast, increasing the perfusion rate produced significantly larger necrotic zones. Doubling the perfusion rate made it possible to reach higher temperatures (>60°C) within significantly shorter time.

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