Photothermographic materials are coated with imaging layers and an antihalation layer between the support and thermally developable imaging layers on one or both sides of the support. Such materials can be arranged in association with one or more phosphor intensifying screens capable of providing emission at a predetermined wavelength in imaging assemblies. These imaging assemblies can be exposed to X-radiation and thereby excited to form a latent image in the photothermographic material that can eventually be used for medical diagnosis. The antihalation layers contain radiation absorbing compounds (such as a UV-radiation absorbing compounds) that absorb radiation at the predetermined wavelength (for example at 300 to 450 nm) and have limited absorption at higher wavelengths.