Ablation treatment planning comprises: acquiring a three-dimensional (3D) image data set of a region of interest; introducing 3D model data of an ablation volume into the 3D image data set; and drawing, as a 2D image, what remains of a cross sectional multiplanar reformatting (MPR) slice of the region of interest and the ablation volume within an MPR plane by virtue of using the MPR plane as a clipping plane. The introduction is doable by tagging image pixels using a stencil buffer and possibly by culling specific inside areas and/or outside areas of the ablation volume. An ablation volume, for, e.g., receiving a cryoablation needle to eliminate tumor tissue and having any arbitrary shape, may be visualized within a 3D image space by drawing 2D images in any desired MPR plane such that also oblique orientations of the ablation volume can be represented. Subsequently, an ablation needle may be guided to a location and in an orientation as previously planned.