The present invention relates to the use of dark field X-ray images in an ablation treatment of a tumour. By acquiring dark field X-ray images displaying the region of interest targeted in the ablation treatment, information can be derived which allows taking a decision on terminating the ablation treatment. A set of dark field X-ray images is received (101), which is acquired at different time instants and comprises the region of interest. Dark field X-ray images of the set are compared (102), for example by determining difference images between the individual images. If during that comparison a change in the dark field X-ray images is detected over time in the region of interest, then a signal is generated (103) indicating a change has occurred. That signal may indicate that healthy tissue is being affected instead of the tumour and that consequently the ablation treatment should be ended.
