MR elastography is a good response parameter for microwave ablation liver tumors

Objectives: To determine the response of hepatic tissue to percutaneous microwave ablation (MWA) of liver tumors via MR elastography in a clinical setting using MRI and MR elastography. Methods: 51 Patients (28 m, 23f) underwent MWA of liver tumors (HCC: 20, metastasis: 31) and received MRI and MR elastography immediately before and 24 h after MWA. Retrospective analysis included pre- and post-ablative tumor extent, T1/T2 mapping and stiffness values as well as the duration and energy dose of the MWA session. Results: Total liver stiffness increased by 4.3% from 3.31 kPa to 3.45 kPa (p = 0.036). Total liver stiffness post-MWA significantly correlated with the duration of the MWA session (r = 0.369, p = 0.008). The higher the baseline tumor stiffness was, the more energy had to be applied in MWA (r = 0.391, p < 0.001) and the longer the duration of the session (r = 0.391, p = 0.007). Healthy parenchyma stiffness increased by 3.5% from 3.55 kPa to 3.68 kPa (p = 0.142) and was strongly influenced by the cumulative energy (r = 0.436, p < 0.001), the duration (r = 0.458, p < 0.001) and the energy intensity (r = 0.458, p < 0.001) of MWA. 43 patients had a technically successful ablation result (margin >= 5 mm). Those with successful ablation had increased ablation margin stiffness (5.3 kPa vs. 4.6 kPa, p = 0.26) and had received higher ablation intensity than those with unsuccessful ablation (5.73 kJ/min vs. 5.03 kJ/min, p = 0.002). Conclusion: Additional MRE may be used before and after MWA to assess treatment response and collateral tissue damage after MWA. Baseline tumor stiffness helps finding the appropriate MWA parameters.

Automated summary

This study investigates the response of hepatic tissue to percutaneous microwave ablation (MWA) of liver tumors using MRI and MR elastography in a clinical setting. The results demonstrate that total liver stiffness and healthy parenchyma stiffness increase after MWA. The response to MWA is influenced by the duration and energy dose of the treatment session, as well as the baseline tumor stiffness. Successful ablation is associated with increased ablation margin stiffness and higher ablation intensity.