The lungs are the darkest part of the chest x-ray because they are the least dense.Ī chest x-ray results in an effective radiation dose of 0.1 mSv, which is the equivalent of natural background radiation for 10 days, or about three flights from the East Coast to the West Coast of the United States (each flight results in 0.03 mSv of radiation exposure, because being at higher altitude results in less protection from cosmic rays). You can see that part of the left lung overlaps the heart. Clavicle: I’ve underlined the clavicle (collarbone) in blue.Air in the stomach is normal, and is referred to as the “gastric bubble.” Stomach: The stomach isn’t outlined, but its position is indicated by the green label.The liver is on the right of the patient (left of the picture) and looks like smooth grey on a normal chest x-ray. Liver: The liver isn’t outlined, but its position is indicated by the purple label.Diaphragm: The diaphragm is the thin dome-shaped muscle that helps with breathing (and hiccups).
The left side of the patient is the right side of the picture.
Recall that in most people the heart points down and to the left, which you can see here.
Heart and Great Vessels: The heart and some of the great vessels (including the aorta) are outlined in red. Here, I’ve outlined a few more structures: See if you can identify the back ribs on the side where the front ribs are highlighted, and if you can identify the front ribs on the side where the back ribs are highlighted. The posterior ribs are underlined in light blue, and look more horizontal. If you feel your own rib cage in the front, you can recognize the downward-pointing angle. Here, the anterior ribs are underlined in yellow, and point more diagonally downwards. On a chest x-ray, you can see both the front sections and the back sections of the ribs, just like the shadow of a cage projected onto a wall. Recall that the ribs wrap all the way around the front and the back of the chest to protect the lungs and heart. Here I’ve added yellow and blue lines to show the difference between the anterior sections of the ribs (front, in yellow) and posterior sections of the ribs (back, in blue). In birds, the collarbones are fused to form the “wishbone”).Īnterior vs. You can also see the clavicle, a v-shaped bone across the top (aka the “collarbone”. There are actually 12 ribs on each side ribs 1, 11, and 12 are not numbered here. In the figure above, the ribs have been numbered 2 through 10. The bones appear white because they are hard, mineralized, and block x-rays effectively.Ĭhest X-Ray: Ribs. The lungs appear black because they are spongy with a lot of air content. Darker colors indicate less dense material, and lighter colors indicate more dense material. But in order to understand what these abnormal findings look like on a chest x-ray, it’s important to first learn what a healthy chest x-ray looks like.Ĭheck out “ Anatomy for Radiology: Chest” for a review of basic chest anatomy. A large number of these procedures are projectional x-rays (commonly just called “x-rays”), where a very small dose of radiation is used to create a 2-D pictures of the chest, abdomen, pelvis, or limbs.Ĭhest x-rays in particular can be used to identify a variety of findings, including pneumonia, pneumothorax (air pockets inside the chest), heart failure, rib fractures, lung masses, big lymph nodes, effusions (extra fluid in the chest), and hernias through the diaphragm, among other conditions. X-rays are the oldest and most popular form of radiology imaging, and automated interpretation of chest x-rays is a a fun machine learning task. In this post, I’ll introduce the basics of chest x-ray interpretation.Įvery year medical personnel perform 3.6 billion medical procedures involving ionizing radiation.
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