Introduction: Malignant tumours in the liver are divided into primary liver cancers and liver metastases. Among primary liver cancers, hepatocellular carcinoma (HCC) accounts for 75-85% and is globally the fourth most common cause of cancer related death. Colorectal cancer (CRC) is the second most common cause of cancer related death. As many as 25-50% of all CRC-patients will be diagnosed with liver metastases, either at the time of diagnosis of their primary cancer, or later during progression of their disease. Surgery is the primary treatment option for colorectal liver metastases (CRCLM). When surgery is not a possible, either due to an insufficient future liver remnant (FLR), or that the patient is not fit for extensive surgery, ablation therapies can be an alternative. Thermal ablation strategies can widen treatment options for extensive liver disease, for oligometastatic disease and for small, potentially resectable tumours, to spare liver parenchyma. The most common thermal ablation techniques for liver tumours are radio-frequency ablation (RFA) and microwave ablation (MWA). The goal is to induce heat within the tumour including a surrounding margin of normal liver to create coagulative necrosis. Irreversible electroporation (IRE) is a non-thermal ablation technique that uses multiple electrodes to administer short pulses of direct current at high voltage to induce permanent pores in the lipid bilayer of the cell walls, disrupting the homeostasis and making the cells go into apoptosis. Since there is only a small amount of heat created just around the electrodes, IRE can be used to treat tumours close to heat-sensitive structures such as major bile ducts and larger hepatic vessels. The placement of the applicators in ablative treatment is one of the main parameters for success, even more so in IRE where several electrodes are placed around the tumour. For optimal treatment effect, they need to be as parallel as possible and at equal depth around the tumour. Different radiological guiding methods are ...