Science

How do X-rays work?

X-rays are a form of light with the incredible ability to pass through solid objects and reveal otherwise hidden details to radiologists, such as bone structure. Over the last century, X-rays have become a crucial component of the modern doctor’s office and are one of the first choices for diagnosis.

So how do these light waves work to expose what is happening inside our bodies? Let’s take a brief look at the history and science behind X-rays to better understand how they are utilized in hospitals around the world today.

Accidental discovery of the X-ray

Gloved hands holding up an x-ray of someones teeth and jaw
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Like penicillin, this crucial health-care technology was discovered by accident. In 1895, German scientist Wilhelm Roentgen was conducting experiments with electricity in his laboratory. He wanted to observe how electricity would behave in a vacuum, and to do this, he removed as much air as he could from a tube. This caused the electrons within to begin moving and interacting with the anode inside the tube. An anode is an electrode through which an electrical current enters a device.

When the electrons impacted the anode, they began sending off X-rays, an undiscovered wavelength of light. The X-rays passed through a heavy cardboard barrier that was set up in the lab, causing a fluorescent bulb that was behind it to glow. Roentgen began experimenting to see what objects would allow the X-rays to still pass through them. Eventually he put his hand in between the tube and a fluorescent screen, and his bone structure was projected onto the surface of the screen.

How do X-rays work?

Medical technician and patient interacting with X-ray diagnostic machine in hospital
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Like radio waves, X-rays are a form of light that is not visible to humans. X-rays’ travel is not inhibited by physical objects with low density, such as human skin and tissue, much like regular light waves are not inhibited by a translucent screen. However, X-rays’ travel is inhibited by denser objects, such as human bones.

To create the X-ray prints we are familiar with today, all that is needed is an X-ray-producing object and some film. The X-ray source is pointed at the area of the body that is under examination while the film is placed behind it. X-rays are released, pass through the body, and hit the film. Less dense areas show up as black or gray, having received most of the X-rays that passed through, and dense areas show up as white, since more X-rays were stopped. This allows doctors to see what is going on under our skin.

How are X-rays used today?

Doctor holding an X-ray diagnostic image, assessing the health of a patient's chest
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While the basic mechanics of X-rays remain unchanged, modern usage of X-rays has become much more complex. By adjusting precise settings, radiologists can use X-rays to detect much more than bone fractures. X-rays can also be used to locate blood clots, cancerous cells, and tumors.

While many of the most well-known uses of X-rays are diagnostic in nature, there are others. They can also be used to perform mammographs, computed tomography (which creates a 3D model of body parts), and fluoroscopy, which allows doctors to view movement in the body. They are also used in radiation treatment for cancer patients.

Are X-rays safe?

Up close view of X-ray imaging of a patient's brain, with multiple scans
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While overexposure to radiation is a very real danger to humans, when used appropriately, the benefits that X-rays can provide far outweigh any health risks they pose. X-rays can detect diseases and problems that will hurt you far sooner than professional X-ray use will.

That said, the risks for harmful side effects are more pronounced in younger people. As such, doctors use ultrasounds and MRIs to view images of a developing baby, and X-rays have special settings for use on children.