Treatment plan evaluation tool

A treatment plan evaluation tool comprising a processor and/or controller configured for calculating a quality indicator for a radiotherapy treatment plan,

• wherein the radiotherapy treatment plan originates from a planning image, wherein the planning image is a magnetic resonance imaging (MRI) image acquired under a presence of a main magnetic field having a magnetic field inhomogeneity;
• wherein the treatment plan evaluation tool is further configured to receive information about the magnetic field inhomogeneity and wherein the treatment plan evaluation tool is further configured to calculate the quality indicator for the radiotherapy treatment plan by comparing the magnetic field inhomogeneity within an organ with a preset limit for the magnetic field inhomogeneity;
• wherein the treatment plan evaluation tool is configured to weight the quality indicator for the radiotherapy treatment plan by organ type, wherein distortions in the planning image caused by the inhomogeneity in the magnetic field get a higher weight when they are at or near a sensitive or critical structure or organ;
• and
• wherein the treatment plan evaluation tool is further configured to weight the quality indicator for the radiotherapy treatment plan by radiation beam orientation.