A lung opacity caused by grid artifact.
D003937:Diagnosis, Differential; D006801:Humans; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation; D013679:Technology, Radiologic; D014963:X-Ray Intensifying Screens