Imaging method and system for verification of a treatment plan in hadron therapy

An imaging method and system for verification of a treatment plan (A). A phantom volume (V) is provided consisting of a material (10m) having dose absorbing properties similar to a biological tissue according to the treatment plan (A). Dose parameters (Q) of a hadron beam (B) are set according to the treatment plan (A). The hadron beam (B) is directed into the phantom volume (V) according to the dose parameters (Q). Light (L) emitted from the phantom volume (V) is measured. A dose distribution (D) of the hadron beam (B) in the phantom volume (V) is calculated based on the measured light (L). The light (L) is measured by imaging a lateral side (14,15) of the phantom volume (V) while the material (10m) of the phantom volume (V) comprises at least 90 mass percent water.