A dose planning software for determining isocenter locations in a target volume for use at a radiation therapy system, said system comprising a radiation therapy unit having a fixed radiation focus point, wherein a spatial dose distribution surrounding the focus point can be changed, wherein radiation is directed to said focus point, said dose planning software being configured to execute: a) obtaining a target volume of a region of a patient to be treated during a treatment of a patient in a radiation therapy unit; b) calculating a curvature of a target surface based on the obtained target volume; c) performing a first isocenter location procedure including: c1) selecting starting voxels on the surface of the target based on selection curvature criteria, c2) evaluating potential isocenter locations along normal directions of the surface and respective isodistance surfaces in respective starting voxel in a direction inwards from the surface, wherein said normal directions are subsequently calculated from the surface of the target to respective isodistance surfaces inwards from respective surface; c3) selecting a location along said normal directions for placing of an isocenter, d) performing a second isocenter location procedure including: d1) identifying a median axis of said target volume or center point of said target volume, d2) placing isocenters at locations along said median axis, d3) placing isocenters in said target volume based on a distance to existing isocenters and to the target surface, and e) providing an isocenter location distribution in said target based on the isocenters placed in said target volume in said first and second isocenter location procedures. a) obtaining a target volume of a region of a patient to be treated during a treatment of a patient in a radiation therapy unit; b) calculating a curvature of a target surface based on the obtained target volume; c) performing a first isocenter location procedure including: c1) selecting starting voxels on the surface of the target based on selection curvature criteria, c2) evaluating potential isocenter locations along normal directions of the surface and respective isodistance surfaces in respective starting voxel in a direction inwards from the surface, wherein said normal directions are subsequently calculated from the surface of the target to respective isodistance surfaces inwards from respective surface; c3) selecting a location along said normal directions for placing of an isocenter, c1) selecting starting voxels on the surface of the target based on selection curvature criteria, c2) evaluating potential isocenter locations along normal directions of the surface and respective isodistance surfaces in respective starting voxel in a direction inwards from the surface, wherein said normal directions are subsequently calculated from the surface of the target to respective isodistance surfaces inwards from respective surface; c3) selecting a location along said normal directions for placing of an isocenter, d) performing a second isocenter location procedure including: d1) identifying a median axis of said target volume or center point of said target volume, d2) placing isocenters at locations along said median axis, d3) placing isocenters in said target volume based on a distance to existing isocenters and to the target surface, and d1) identifying a median axis of said target volume or center point of said target volume, d2) placing isocenters at locations along said median axis, d3) placing isocenters in said target volume based on a distance to existing isocenters and to the target surface, and e) providing an isocenter location distribution in said target based on the isocenters placed in said target volume in said first and second isocenter location procedures.