Microwave ablation in porcine livers applying 5-minute protocols: influence of deployed energy on extent and shape of coagulation.

PURPOSE: To evaluate the influence of deployed energy on extent and shape of microwave (MW)-induced coagulation in porcine livers applying 5-minute protocols. MATERIALS AND METHODS: MW ablations (n = 25) were performed in ex vivo porcine livers (n = 8). Ablation time was 5 minutes. Five study groups were defined, each with different power output: I, 20 W (n = 5); II, 40 W (n = 5); III, 60 W (n = 5); IV, 80 W (n = 5); and V, 105 W (n = 5). Extent and shape of white coagulation was evaluated macroscopically, including short diameter, volume, front margin, coagulation center (distance between center of short diameter of coagulation and applicator tip), and ellipticity index (short diameter/long diameter). Deployed energy was also analyzed. RESULTS: Short diameter and volume were significantly different (P<.001 and P<.001) between the groups: I, 23.0 mm and 11.1 cm(3); II, 12.4 mm and 12.4 cm(3); III, 27.0 mm and 17.6 cm(3); IV, 31.0 mm and 29.2 cm(3); and V, 35.0 mm and 42.3 cm(3). Front margin and coagulation center were also significantly different (P<.05 and P<.001): I, 6.0 mm and 13.0 mm; II, 8.0 mm and 11.0 mm; III, 8.0 mm and 14.0 mm; IV, 8.0 mm and 18.0 mm; and V, 10.0 mm and 19.0 mm. Ellipticity index was not significantly different. Deployed energy was significantly different (P<.001): I, 5.7 kJ; II, 11.0 kJ; III, 15.5 kJ; IV, 21.6 kJ; and V, 26.6 kJ. CONCLUSIONS: Extent, but not shape, of MW-induced coagulation depends on the deployed energy. Applying the protocols described in this study, significantly different coagulation volumes can be created with an ablation time of 5 minutes but different power output.

Treatment Failure After Image-Guided Percutaneous Radiofrequency Ablation (RFA) of Renal Tumors - A Systematic Review with Description of Type, Frequency, Risk Factors and Management.

Background Radiofrequency ablation (RFA) is an established treatment for small renal tumors. The objective of this review is to systematically assess the type, frequency, risk factors and management of treatment failure after image-guided percutaneous RFA of renal tumors. Method 10 studies (967 patients, 1033 tumors) with a mean/median follow-up of ≥ 30 months were systematically identified and analyzed. Results and Conclusion Image-guided percutaneous RFA of localized renal tumors is very effective. The most common type of treatment failure is residual unablated tumor (5.9 %), followed by local tumor progression (4.7 %). De novo tumors in the kidneys occur in 1.3 % of cases and extra-renal metastases in 2.0 %. Local tumor progression, de novo tumors in the kidneys and extra-renal metastases occur predominantly later than 12 months after initial RFA. Tumor size > 3 cm and central tumor location are the major risk factors for treatment failure. In the case of treatment failure, repeated RFA shows high success rates (86.3 % for residual unablated tumors and 87.5 % for local tumor progression). Key Points: · Treatment failure can be subdivided into residual unablated tumor and local tumor progression.. · Residual unablated tumor occurs in 5.9 % of cases.. · Local tumor progression occurs in 4.7 % of cases.. · Tumor size and location are the major risk factors for treatment failure.. · Repeated RFA is effective and commonly used for management.. Citation Format · Vollherbst D, Bertheau R, Kauczor H et al. Treatment Failure After Image-Guided Percutaneous Radiofrequency Ablation (RFA) of Renal Tumors - A Systematic Review with Description of Type, Frequency, Risk Factors and Management. Fortschr Röntgenstr 2017; 189: 219 - 227.