Safety margin assessment after microwave ablation of liver tumors: inter- and intrareader variability

  • Dr. Jan Schaible Doctor
  • Dr. Benedikt Pregler
  • Dr. Wolf Bäumler
  • Dr. Ingo Einspieler
  • Prof. Dr. Ernst-Michael Jung
  • Prof. Dr. Christian Stroszczynski
  • PD. Dr. Lukas P Beyer


Objective:To evaluate the inter- and intrareader variability of the safety margin assessment after microwave ablation of liver tumors using post-procedure computed tomography (CT) images.

Methods:A retrospective analysis of 58 patients who underwent MWA of primary or secondary liver malignancies (46 hepatocellular carcinoma, 9 metastases of a colorectal cancer and 3 metastases of pancreatic cancer) between September 2017 and June 2019 was conducted. Three readers estimated the minimal safety margin in millimeters using side-by-side comparison of the 1-day pre-ablation CT and 1-day post-ablation CT and judged whether ablation was complete or incomplete. One reader estimated the safety margin again after 6 weeks. The aim was to detect inter- and intrareader differences as well as to determine the sensitivity and specificity of identification remnant tumor tissue. Magnetic resonance imaging (MRI) after 6 weeks was the gold standard. 

Results: The intraclass correlation coefficient (ICC) for estimation of the minimal safety margin of all three readers was 0.357 (95%-confidence interval 0.194 - 0.522). The ICC for repeated assessment (reader 1) was 0.774 (95%-confidence interval 0.645 - 0.860). Sensitivity and specificity of the detection of complete tumor ablation, defined as no remnant tumor tissue in 6 weeks follow-up MRI, was 93%/82%/82% and 33%/17%/83%.

Conclusion: In clinical practice the safety margin after liver tumor ablation is often assessed using side-by-side comparison of CT images. In our study we were able to show, that this technique has a poor reliability (ICC 0.357). From our point of view, this proves the necessity of new technical procedures for the assessment of the safety distance.

How to Cite
Schaible, D. J., Pregler, D. B., Bäumler, D. W., Einspieler, D. I., Jung, P. D. E.-M., Stroszczynski, P. D. C., & Beyer, P. D. L. P. (2020). Safety margin assessment after microwave ablation of liver tumors: inter- and intrareader variability. Radiology and Oncology, 54(1), 57-61. Retrieved from