A system for assisting a surgeon in placing at least one ablation device into a treatment region of a patient, the system comprising: at least one computer system comprising a display, a user interface and software configured to: receive patient image data of the treatment region; generate an image of the treatment region on the display; identify the treatment region to ablate with a target; identify tissue properties of the treatment region; and generate treatment parameters (118, 120) for the at least one ablation device; wherein the software is further configured to: identify patient anatomy surrounding the treatment region; identify tissue properties of tissue surrounding the treatment region; perform thermal modeling of the treatment region based on the tissue properties of the treatment region and the tissue properties of the tissue surrounding the treatment region; calculate a number of ablation devices required to ablate the treatment region and a location and orientation of each ablation device in the treatment region based on a size of the target and the thermal modeling of the treatment region performed based on the tissue properties of the treatment region and the tissue properties of the tissue surrounding the treatment region, wherein the ablation devices are cryoprobes (122, 124); calculate an ablation zone based on the number of ablation devices required to ablate the treatment region and the location and orientation of each ablation device in the treatment region, wherein the ablation zone includes a composite isotherm comprising individual isotherms for each of the number of cryoprobes (122, 124) calculated to ablate the treatment region; and display on the computer system display (a) the number of ablation devices required to ablate the treatment region and the location and orientation of each ablation device in the treatment region and (b) the ablation zone. receive patient image data of the treatment region; generate an image of the treatment region on the display; identify the treatment region to ablate with a target; identify tissue properties of the treatment region; and generate treatment parameters (118, 120) for the at least one ablation device; wherein the software is further configured to: identify patient anatomy surrounding the treatment region; identify tissue properties of tissue surrounding the treatment region; perform thermal modeling of the treatment region based on the tissue properties of the treatment region and the tissue properties of the tissue surrounding the treatment region; calculate a number of ablation devices required to ablate the treatment region and a location and orientation of each ablation device in the treatment region based on a size of the target and the thermal modeling of the treatment region performed based on the tissue properties of the treatment region and the tissue properties of the tissue surrounding the treatment region, wherein the ablation devices are cryoprobes (122, 124); calculate an ablation zone based on the number of ablation devices required to ablate the treatment region and the location and orientation of each ablation device in the treatment region, wherein the ablation zone includes a composite isotherm comprising individual isotherms for each of the number of cryoprobes (122, 124) calculated to ablate the treatment region; and display on the computer system display (a) the number of ablation devices required to ablate the treatment region and the location and orientation of each ablation device in the treatment region and (b) the ablation zone. identify patient anatomy surrounding the treatment region; identify tissue properties of tissue surrounding the treatment region; perform thermal modeling of the treatment region based on the tissue properties of the treatment region and the tissue properties of the tissue surrounding the treatment region; calculate a number of ablation devices required to ablate the treatment region and a location and orientation of each ablation device in the treatment region based on a size of the target and the thermal modeling of the treatment region performed based on the tissue properties of the treatment region and the tissue properties of the tissue surrounding the treatment region, wherein the ablation devices are cryoprobes (122, 124); calculate an ablation zone based on the number of ablation devices required to ablate the treatment region and the location and orientation of each ablation device in the treatment region, wherein the ablation zone includes a composite isotherm comprising individual isotherms for each of the number of cryoprobes (122, 124) calculated to ablate the treatment region; and display on the computer system display (a) the number of ablation devices required to ablate the treatment region and the location and orientation of each ablation device in the treatment region and (b) the ablation zone.