RF ablation (RFA) is used for thermal ablation of tumors in which the RF electrode is placed in the tissue under image-guidance. Because of the good tumor visibility and the lack of ionizing radiation, MR-guided RFA is the method of choice. Additionally, with the help of MR thermometry the RF ablation can be monitored during the intervention. Unfortunately, the imaging of an MR scanner is highly sensitive to interferences caused by external electrical signals. In this paper the high-power RF ablation signal of a commercially available medical therapy device is made MR-compatible. A design of a low-pass filter with high-power compatibility is presented. The filter performance is demonstrated by means of simulations and measurements.