Method for determining radiation attenuation in a positron emission tomography scanner

A device for a positron emission tomography system for determining radiation attenuation as a result of a non-phantom object in a positron emission tomography scanner of the positron emission tomography system, the device comprising:

• a control unit to actuate a positron emission detector of the positron emission tomography scanner;
• and
• an image-calculation unit to receive raw radiation data acquired by the positron emission detector and to reconstruct image data from the raw radiation data, wherein the device is configured
• to acquire first raw radiation data of a phantom object, which includes a positron emission source, arranged in the positron emission tomography scanner, while the non-phantom object is not arranged in the positron emission tomography scanner,
• to calculate a first image of the phantom object from the first raw radiation data,
• to identify preliminary radiation attenuation of the non-phantom object arranged in the positron emission tomography scanner,
• to acquire second raw radiation data of the phantom object while the non-phantom object is arranged in the positron emission tomography scanner,
• to calculate a second image of the phantom object from the second raw radiation data taking into account the preliminary radiation attenuation, and
• to determine the radiation attenuation on the basis of the first image and the second image.