Because a chest x-ray is an overlapping image of the anterior and posterior positions, a chest x-ray is not as comprehensive as a chest CT. A chest radiograph can look at the ribs, lungs, and chest cavity, as well as the mediastinum and the large blood vessels of the heart to see what the images have changed into and what diseases they are consistent with. For example, a chest X-ray can look at the ribs to see if there is a fracture and the extent of the fracture, and also to see if there is a bone tumor in the ribs. A chest X-ray can look at lung tissue, pneumonia, lung tumors, etc. A chest X-ray can also look at the chest cavity, like whether there is a pneumothorax or pleural effusion after a trauma. Chest radiographs look at the heart mainly to see which heart disease is consistent with changes in the heart shadow, and to see if there is a bulge or protrusion in one of the major blood vessels.