A method is disclosed for operating a radiation therapy system. The radiation therapy system includes a magnetic resonance apparatus. In an embodiment of the method, an irradiation plan is received for a patient. While the patient is arranged in the radiation therapy system and a hyperpolarized contrast agent has been administered, magnetic resonance data of the patient is acquired. In the magnetic resonance data, molecular irradiation target areas are determined on the basis of the hyperpolarized contrast agent and the received irradiation plan is corrected as a function of the molecular irradiation target areas determined in the magnetic resonance data. A molecular irradiation target area relates to an area of the patient with a molecular property.
