in an imaging method and a tomosynthesis apparatus , a two - dimensional low - energy image of the predetermined volume segment is obtained after administration of a contrast agent , followed by a two - dimensional high - energy image and then a high - energy tomosynthesis of the predetermined volume segment is obtained with a high total radiation dose that is significantly higher than the low radiation dose . the two - dimensional low - energy image is subtracted from the two - dimensional high - energy image to generate a result with which the concentration of the contrast agent is visible . additionally , in a time interval in which an enrichment or a washing - out of the contrast agent occurs within the predetermined volume segment , a tomosynthesis of the predetermined volume segment is automatically implemented to show the concentration of the contrast agent in the predetermined volume segment .