A system for planning an ablation procedure, the system comprising: a plurality of ablation probes (112, 112') having distinct characteristics; and a generator assembly configured to couple to at least one of the plurality of ablation probes (112, 112'), the generator including: a generator module configured to generate microwave or radiofrequency ablative energy; a database for storing probe parameters and a set of ablation shapes associated with said ablation probes; a user interface comprising a display, the user interface being configured to receive a user-selectable input enabling a user to select an ablation shape from the set of ablation shapes and to select at least one probe parameter; and a processor configured to cause the user interface to display a preview of at least one of the plurality of ablation probes, suitable for forming an ablation volume corresponding to the user-selected ablation shape based on the at least one probe parameter (307, 307'), to enable the user to select one of the ablation probes to be coupled to the generator, wherein the user interface includes a rotation user interface element (312, 314) configured to rotate the user-selectable ablation shape. a plurality of ablation probes (112, 112') having distinct characteristics; and a generator assembly configured to couple to at least one of the plurality of ablation probes (112, 112'), the generator including: a generator module configured to generate microwave or radiofrequency ablative energy; a database for storing probe parameters and a set of ablation shapes associated with said ablation probes; a user interface comprising a display, the user interface being configured to receive a user-selectable input enabling a user to select an ablation shape from the set of ablation shapes and to select at least one probe parameter; and a processor configured to cause the user interface to display a preview of at least one of the plurality of ablation probes, suitable for forming an ablation volume corresponding to the user-selected ablation shape based on the at least one probe parameter (307, 307'), to enable the user to select one of the ablation probes to be coupled to the generator, wherein the user interface includes a rotation user interface element (312, 314) configured to rotate the user-selectable ablation shape. a generator module configured to generate microwave or radiofrequency ablative energy; a database for storing probe parameters and a set of ablation shapes associated with said ablation probes; a user interface comprising a display, the user interface being configured to receive a user-selectable input enabling a user to select an ablation shape from the set of ablation shapes and to select at least one probe parameter; and a processor configured to cause the user interface to display a preview of at least one of the plurality of ablation probes, suitable for forming an ablation volume corresponding to the user-selected ablation shape based on the at least one probe parameter (307, 307'), to enable the user to select one of the ablation probes to be coupled to the generator, wherein the user interface includes a rotation user interface element (312, 314) configured to rotate the user-selectable ablation shape.