In order to improve the detectability of a structure that is tube-shaped in an imaging method, a method for preparing the structure is specified. A first channel is formed inside an inner wall of an auxiliary device, and a second channel is formed between the inner wall and an outer wall. A first fluid that contains a material for contrast amplification is poured into the structure via the first channel. The first channel is then closed by a swelling element of the auxiliary device being enlarged by pouring a second fluid into the second channel.
