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X-rays are a type of ionizing radiation that can be very harmful to living organisms. They can damage cells and DNA, and even cause cancer. However, the discovery of X-rays revolutionized medicine and changed everything. Surprisingly, X-rays were discovered completely by accident!

In 1895, Wilhelm Roentgen, a professor of physics in Germany, was experimenting with a cathode ray. He was shocked to discover an unrelated group of fluorescent crystals on a nearby table that would begin to glow simultaneously when the cathode ray was switched on. Roentgen concluded that an undiscovered ray was being emitted from the tube, a ray that could pass through substances. He named them X-rays (meaning unknown rays), as the physicist had no idea what they were.

Several weeks after his discovery, he took the first X-ray image of a human, his wife's hand. When she saw her skeletal hand, she said, "I have seen my death!" Before the 20th century, one would have had to cut a person open to find a broken bone or a tumor. Thanks to X-rays, however, doctors could now see inside the human body without invasive procedures.

Today, X-rays are an essential tool in medicine, used to diagnose a wide range of medical conditions such as fractures, lung infections, dental problems, and more. They are also used in industries like manufacturing, aerospace, and transportation to check for faults and ensure safety. Despite their usefulness, it is important to use X-rays judiciously and with caution, as they can cause harm if not used properly.

Roentgen's first x-ray machine, which he used to take the first x-ray image on a human

X-Ray Definition

X-rays are a form of electromagnetic radiation, similar to visible light. Unlike light, however, x-rays have higher energy and can pass through most objects, including the body. Medical x-rays are used to generate images of tissues and structures inside the body. If x-rays traveling through the body also pass through an x-ray detector on the other side of the patient, an image will be formed that represents the “shadows” formed by the objects inside of the body.

One type of x-ray detector is photographic film, but there are many other types of detectors that are used to produce digital images. The x-ray images that result from this process are called radiographs.

The electromagnetic spectrum
The electromagnetic spectrum. X-rays have higher energy than visible light.

Examples of X-Rays

X-rays are a type of electromagnetic radiation that are produced by hot objects in space, like pulsars and black holes. These x-rays travel at the speed of light and can reach Earth after many years. However, our atmosphere blocks them, so we are safe from their harmful effects.

But did you know that there are also natural sources of x-ray radiation on Earth? Low levels of radioactive materials like radon gas, uranium, and thorium can be found in the soil and underground. These sources contribute to background radiation.

Scientists can also create x-rays artificially by using high voltage to accelerate electrons into a metal target. When the electrons hit the metal, they slow down and release their energy as x-rays. This is the same process that Wilhelm Roentgen used in his original experiment. Today, medical and industrial x-ray machines use this technique to generate x-rays for various applications.

While x-rays can be harmful in high doses, they are also extremely useful in medicine and industry. X-rays can help doctors diagnose broken bones, locate tumors, and even treat cancer. In industry, x-rays can be used to inspect materials for defects and weaknesses.

So the next time you hear the term x-ray, remember that they come from many sources, both natural and artificial. And while they can be dangerous, they also have many important uses that benefit our society.

Uses of X-Ray in Medicine

Radiology is the science of using high-energy radiation such as x-rays in medicine, especially for the treatment and diagnosis of disease.

Internal Imaging

Roentgen realized their potential for medical uses. Soft organs, like the lungs, heart, bladder, or skin, would only partially absorb x-rays at different rates, depending on their density. However, bones would almost completely absorb all the incoming x-ray radiation. Bones have calcium, which has a higher atomic number than other body tissues like hydrogen, oxygen, or carbon. This contributes to their high radiological density, which is a measure of how much incoming radiation a substance absorbs based on its density.

To take an x-ray image, a patient is positioned between an x-ray generator and a photographic plate. The radiographer, who operates the machinery, stands behind a thick lead plate to protect themselves from the harmful x-rays. The patient must stay still as any movement can cause blurry images. As the photographic plate absorbs the x-rays, it darkens, while the bones absorb the x-rays and appear as white shadows. This high contrast generates a radiograph (x-ray image). X-rays are a valuable tool in medicine, helping doctors diagnose broken bones, locate tumors, and treat cancer. However, they can be dangerous in high doses, which is why it's crucial to use them carefully and with proper protection.

Direct imaging of a bone using x-ray, adapted from image

X-ray Risks

X-rays have a higher penetrating power that allows detailed internal scans of the human body or other objects. However, the ionizing radiation of an x-ray scan can cause catastrophic damage to our DNA. The molecules that make up our genes can mutate, which might eventually lead to cancer! Before the harmful effects of x-rays were exposed, pregnant women were x-rayed to check the health and development of the fetus. Some shoe stores even used to offer a free x-ray scan of your foot with the purchase of a pair of shoes! Nowadays, health professionals always judge if an injury is worth the health risk of an x-ray.

To measure how much radiation a living organism has been exposed to, we use the standard unit sievert (Sv). The millisievert is more commonly used as humans in the UK are usually only exposed to about 2.7 millisieverts per year, making it a more convenient measurement. One sievert is equal to one joule per kilogram (1 Sv = 1 J/Kg). This means that if one kilogram of human tissue absorbed one joule of energy from radiation, they would have been exposed to exactly one sievert. While x-rays are incredibly useful in medicine, it's crucial to use them carefully to avoid any unnecessary exposure to radiation that might increase the risk of cancer.

Types of X-Ray

Medical professionals use a variety of x-rays to check a patient's health. Sometimes, multiple x-rays are needed to create a 3D image, called a CT scan.

Different types of x-rays are used for different parts of the body. Abdominal x-rays show organs in the abdomen, while chest x-rays check the heart and lungs.

Dental x-rays help with oral health, and sinus x-rays create images of the spaces in the front of your skull. Skeletal x-rays detect fractures or broken bones, and only scan the specific bone that is injured. By using different types of x-rays, medical professionals can see inside the body and check for different medical issues.

Other x-ray techniques used in medicine include:

Radiation Therapy to Treat Cancer

Since we just talked about how radiation can cause cancer, you might wonder how x-rays and other types of high-energy radiation can be used to treat cancer. High-energy radiation is used to kill cancer cells by damaging their DNA, just like it does to our healthy cells. When radiation is used to treat cancer, the doses are thousands of times higher than when it is used for imaging. This means that it can be harmful and sometimes have serious side effects, such as hair loss, fatigue, and diarrhoea. But there are a couple of smart ways to target cancerous cells that hurt other cells in the body as little as possible. With external beam radiation therapy, we use a machine that sends a narrow beam of x-rays at your cancer from the outside. This beam only hits a small area of your body. We can also use internal radiation therapy, which involves putting a source of radiation inside the body near the cancerous cells or tumour. This can be done by eating the drug, getting it injected into the bloodstream, or even putting it there surgically.

X-rays - Key Takeaways

X-rays have a frequency between 31016 Hz and 31019 Hz, and, after gamma rays, they are the second most powerful part of the electromagnetic spectrum. Ionizing radiation, which is what X-rays are, can cause cancer. Some things that are opaque to visible light can be seen through by X-rays. X-rays with more energy can go deeper into a substance. X-rays can be made by many hot things in space, by radon gas, and by radioactive materials in the Earth. X-rays can be made in a lab by sending a stream of electrons into a metal target at a high speed across a high voltage. X-rays are made when the electrons slow down and lose their kinetic energy. Soft tissue in the body only absorbs some of the x-rays, but denser things like bone absorb almost all of them. This lets a photograph form on a plate with a lot of contrast.


What is an x-ray?

An x-ray is a type of electromagnetic radiation, like visible light. X-rays have higher frequencies (3×1016- 3×1019 Hz) and energy than visible light. They are so energetic that they are a type of ionising radiation, which can be very harmful to living things.

What are the uses of x-rays?

X-rays have many different applications. Some examples are their use in the field of medicine to check on the health of a patient or to help in cancer treatments. Airport security uses x-rays to examine the contents of travellers' belongings and we study x-rays to learn more about objects in space.

What are examples of x-ray? 

X-rays are naturally produced by hot objects in space. On Earth, natural x-ray sources include radon gas or radioactive deposits in the soil.

What are the different types of x-ray? 

There are many different types of internal imaging x-rays used by health professionals. These include abdominal, chest, dental, sinus and skeletal x-rays. More advanced techniques are called angiography, fluoroscopy and mammography.

What are the uses of x-ray in medicine?

Internal imaging allows health professionals to examine the bones, organs and structures within the body. While external beam and internal radiation therapy are used to fight cancer.

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