In a quality control method and computer for planning radiotherapy of patient, magnetic resonance (MR) image data, acquired from a planning volume of a patient, are provided to a computer and are used in the computer to generate a first electron density map of the planning volume. A second electron density map is generated using the first electron density map, wherein a value of electron density for a bone region in the planning volume is reduced compared to the first electron density map. First and second radiation dose distributions in the planning volume are respectively determined from the radiotherapy plan and the first electron density map, and the radiotherapy plan and the second electron density map. These distributions are compared in order to generate output information.
