Densities in Chest X-Ray
In interpreting a chest x-ray, you should systematically evaluate mediastinum, lung fields, pleural space, diaphragm, and chest wall. Also evaluate the neck, axilla and abdomen. Important clues can be recognized by looking at the entire chest x-ray.
Basically, you can recognize air, water and bone density on chest x-ray. Lung fields appear dark because of air. Ninety-nine percent of the lung is air. The pulmonary vasculature, interstitium constitute 1% and give the lacy lung pattern. Heart, vessels, liver and diaphragm are liquid density. Vertebrae, sternum and ribs obviously cast a bone density.
Most of the disease states replace air from alveoli with a pathological process which usually is a liquid density and appears white. Having a proper understanding of each of the pathological process is essential. Then we can develop roentgen signs that help us identify the pathological process in chest x-ray.