Tumor diagnostics using imaging techniques is usually the second step and is often carried out without anaesthetizing the animal. X-ray examinations are excellent for visualizing internal structures. The lungs, for example, can be assessed most reliably and quickly using an X-ray. Many tumors metastasize to the lungs at an early stage, so that an X-ray image can provide information about the formation of metastases. For optimal visualization of all lung lobes, 2 to 3 lung images are usually taken.