A medical apparatus comprising: - a radiotherapy apparatus for radiating a target volume; - a magnetic resonance module for acquiring motion tracking magnetic resonance data having high enough temporal resolution to track movement of the target volume and image magnetic resonance data having high enough quality for visualizing the target volume, wherein the data is acquired from a subject of which at least a part is located within an imaging volume, wherein the target volume is within the imaging volume; - a memory for storing machine executable instructions (180, 182, 186, 188, 194); and - a processor for controlling the medical apparatus, wherein execution of the machine executable instructions (180, 182, 186, 188, 194) causes the processor to receive a treatment plan specifying the target volume within the imaging volume and a dose rate of radiation to be emitted by the radiotherapy apparatus, and to repeatedly: - acquire the motion tracking magnetic resonance data and the image magnetic resonance data by controlling the magnetic resonance module with an interleaved pulse sequence; - control the radiotherapy apparatus to radiate the target volume in accordance with the treatment plan; - calculate a dose distribution map descriptive of a radiation dose received by the subject from the radiotherapy apparatus using the motion tracking magnetic resonance data and the treatment plan; - reconstruct a diagnostic image using the image magnetic resonance data; - display on a display the diagnostic image and the dose distribution map; - receive treatment plan update data from a user interface; and - update the treatment plan in accordance with the treatment plan update data, wherein the update of the treatment plan occurs during radiation of the target volume. - a radiotherapy apparatus for radiating a target volume; - a magnetic resonance module for acquiring motion tracking magnetic resonance data having high enough temporal resolution to track movement of the target volume and image magnetic resonance data having high enough quality for visualizing the target volume, wherein the data is acquired from a subject of which at least a part is located within an imaging volume, wherein the target volume is within the imaging volume; - a memory for storing machine executable instructions (180, 182, 186, 188, 194); and - a processor for controlling the medical apparatus, wherein execution of the machine executable instructions (180, 182, 186, 188, 194) causes the processor to receive a treatment plan specifying the target volume within the imaging volume and a dose rate of radiation to be emitted by the radiotherapy apparatus, and to repeatedly: - acquire the motion tracking magnetic resonance data and the image magnetic resonance data by controlling the magnetic resonance module with an interleaved pulse sequence; - control the radiotherapy apparatus to radiate the target volume in accordance with the treatment plan; - calculate a dose distribution map descriptive of a radiation dose received by the subject from the radiotherapy apparatus using the motion tracking magnetic resonance data and the treatment plan; - reconstruct a diagnostic image using the image magnetic resonance data; - display on a display the diagnostic image and the dose distribution map; - receive treatment plan update data from a user interface; and - update the treatment plan in accordance with the treatment plan update data, wherein the update of the treatment plan occurs during radiation of the target volume. - acquire the motion tracking magnetic resonance data and the image magnetic resonance data by controlling the magnetic resonance module with an interleaved pulse sequence; - control the radiotherapy apparatus to radiate the target volume in accordance with the treatment plan; - calculate a dose distribution map descriptive of a radiation dose received by the subject from the radiotherapy apparatus using the motion tracking magnetic resonance data and the treatment plan; - reconstruct a diagnostic image using the image magnetic resonance data; - display on a display the diagnostic image and the dose distribution map; - receive treatment plan update data from a user interface; and - update the treatment plan in accordance with the treatment plan update data, wherein the update of the treatment plan occurs during radiation of the target volume.