An X-ray is a widely used medical imaging procedure that helps doctors and dentists see inside the body to diagnose and monitor health conditions. X-rays are quick, noninvasive, and usually painless. They use a small amount of radiation to create images of bones and teeth as well as the lungs and abdomen. When used in medical care, the benefits of X-rays far outweigh the risks, especially when the procedure is performed with proper safety measures.

An X-ray is a medical imaging test that uses a special form of energy called ionizing radiation to create pictures of structures inside the body. Doctors and dentists often order X-rays to check for problems such as broken bones, dental cavities, lung infections, masses, or other medical conditions where the cause is not clear. X-rays are also used to guide medical procedures, such as placing tubes or devices inside the body.

X-rays are commonly performed in hospitals, clinics, and dental offices. The test is quick and usually takes only a few minutes. There are several types of X-rays, including chest X-rays, bone X-rays, dental X-rays, and specialized studies such as mammography for breast imaging. In some cases, X-rays are combined with contrast agents (special substances that make certain areas of the body show up more clearly in images) to help doctors see blood vessels, the digestive tract, or other internal structures.

Because X-rays expose you to a small amount of radiation, health care providers carefully consider when to order them and use the lowest dose possible to get a clear picture. They follow the “As Low as Reasonably Achievable” (ALARA) principle, which means using the minimum amount of radiation needed for diagnosis. X-rays are an important tool for diagnosing disease, planning treatment, and monitoring recovery.

An X-ray works by sending a beam of radiation through a part of the body while a special type of camera measures how much passes through. Different tissues absorb or block the X-ray beam in varying amounts, depending on their density. Dense structures such as bones block most of the X-rays and appear white on the image, while softer tissues such as muscles and fat appear as shades of gray. Air-filled spaces, such as the lungs or intestines, show up as black areas because they allow the X-rays to pass through easily.

The X-ray beam passes through the body and reaches a detector. In modern systems, a special type of digital camera has replaced X-ray film as the detector to make the image. Radiologists and other qualified health care providers (including dentists) examine these images to look for signs of injury, disease, or other problems.

There are many tests that go beyond taking a simple picture. Some X-ray procedures use contrast agents (usually a liquid that increases density) to improve visibility of certain areas. These agents may be swallowed, injected, or inserted into the body, making blood vessels, organs, or the digestive tract appear brighter or whiter on the X-ray image. One type of X-ray test, called fluoroscopy, replaces the still image with video to provide real-time moving images to help guide procedures or observe organ function. Other tests, such as mammograms, combine X-rays with other equipment, including compression paddles to image a specific organ.

Modern X-ray machines are designed to use the smallest amount of radiation needed to produce clear images, and safety features help protect people being imaged and staff from unnecessary exposure.

People who need an X-ray are usually those with symptoms or health concerns that require a closer look inside the body. These symptoms and health concerns may include suspected bone fractures, joint injuries, dental problems, lung infections, or unexplained pain. X-rays are also used to monitor certain chronic conditions and to guide medical or dental procedures.

Doctors consider several factors before recommending an X-ray, such as the person's age, medical history, and the specific health question. Dentists recommend dental X-rays based on age, symptoms, and cavity risk. Pregnant women or those who believe they may be pregnant should inform their doctor or X-ray technologist, as extra care may be taken to avoid exposing the developing fetus to radiation.

If a person has had many X-rays or other imaging tests that use radiation, the doctor may review their imaging history to avoid unnecessary repeat exams. In some cases, alternative tests that do not use radiation, such as ultrasound or magnetic resonance imaging (MRI), may be considered if they can provide the needed information.

X-rays use ionizing radiation, which can potentially cause harm to living cells. For most routine X-ray exams, the amount of radiation exposure is very low, and the risk of side effects is extremely small. However, repeated or high-dose exposure to radiation in any form can increase the risk of developing cancer later in life.

• The main risk of X-rays is a slight increase in the chance of cancer over a person's lifetime, especially when X-rays are done at a younger age, with higher doses, or when exams are done frequently.
• Some tissues and organs are more sensitive to radiation, such as breast tissue and reproductive organs, so extra care is taken when imaging these areas.
• Children and unborn babies are more sensitive to radiation, so doctors use special precautions and choose alternative tests when possible.
• Rarely, high doses of radiation from certain procedures (such as long or complex fluoroscopy exams) can cause skin reddening, hair loss, or cataracts.
• If a contrast agent is used, some people may experience mild side effects like nausea or discomfort. Rarely, allergic reactions to contrast agents can occur.
• For pregnant women, most routine X-rays do not pose a serious risk to the developing baby, but doctors will carefully weigh the benefits and risks and may use shielding or alternative tests.

Health care providers and imaging technologists follow strict safety guidelines to minimize radiation exposure. People with questions or concerns about the risks should talk to their doctor or radiologist before the exam. If unusual symptoms develop after an X-ray, such as skin changes or signs of an allergic reaction, medical attention should be sought promptly.

Preparation for an X-ray is usually simple and depends on the type of exam. Most routine X-rays require little or no special preparation.

• Women who are pregnant or think they might be pregnant should tell their health care provider or technologist, as special precautions may be needed.
• Remove all jewelry, eyeglasses, or clothing with metal parts, such as zippers or buttons, because metal can interfere with the images.
• For some types of X-rays, a hospital gown may be required.
• For exams that use contrast agents, specific instructions may apply, such as fasting or drinking a special liquid before the test.
• A history of allergies or previous reactions to contrast agents should be shared with the health care provider before the exam.

Following these steps helps ensure that the images are clear and that the procedure is safe.

An X-ray is usually performed in a hospital, clinic, or dental office by a trained radiologic technologist. The procedure typically takes only a few minutes.

During an X-ray, the person is positioned carefully to get the best images of the part of the body being imaged. The body part being imaged will be positioned between the X-ray source and the detector (film or digital sensor).

The technologist may ask the person to stand, sit, or lie down, hold their breath for a few seconds, and sometimes hold a specific position or angle. For dental X-rays, a small device may be placed in the mouth to help capture images from different angles.

For certain types of X-rays, such as those using contrast agents, the agent may be given by mouth, injection, or enema before the images are taken.

Once the person is positioned properly, the technologist operates the X-ray machine from behind a protective barrier or in a separate room to avoid exposure. The X-ray machine is turned on for only a fraction of a second to produce the image. It is important that the person being examined stay still during the procedure, as movement can result in blurry images.

Multiple images may be taken from different angles to provide a complete view of the body part being examined. After the images are taken, the technologist checks them for quality. A radiologist or another qualified health care provider then reviews and interprets the images and creates a report about what those images show. This report will be sent to the doctor who ordered the exam and to the person who had the X-ray.

After an X-ray, most people can return to their normal activities right away. There is no recovery period needed for routine X-rays, and the radiation from an X-ray cannot be felt.

• If a contrast agent was used, a short period of monitoring may be needed for side effects, such as nausea or an allergic reaction.
• The images are reviewed and interpreted by a radiologist or another qualified health care provider, depending on the setting (for example, a dentist may interpret dental X-rays).
• A report or results may be sent to the health care provider who ordered the X-ray, who will explain any findings to the person who had the exam. In the United States, the report will also be available to view in the patient portal. People who had an X-ray will also have access to a link to their images or can request the images from the radiology department.
• If unusual symptoms occur after the exam (such as skin changes or discomfort), contact a health care provider promptly.

Most people do not notice any changes after an X-ray and can continue with their day as usual.

Other imaging tests may be used instead of an X-ray depending on the health question and the part of the body being examined. Alternative imaging tests include:

• Ultrasound, which uses sound waves to create images and does not use ionizing radiation.
• MRI, which uses a strong magnetic field and radio waves to make detailed images and does not use ionizing radiation.
• Computed tomography (CT) scan, which uses X-rays to create cross-sectional images and involves a higher dose of radiation than a standard X-ray but creates much more detailed images.

“The way that an X-ray is performed is going to appear the same no matter what radiology office or hospital you go to, which causes many people to think that all radiology is the same or that factors such as how nice the waiting room is are most important,” says Christopher Gange, MD, a Yale Medicine diagnostic radiologist who specializes in thoracic oncology. “The reality is that the radiologist’s interpretation of the images, which happens behind the scenes after the exam, is what differentiates quality in diagnostic medicine. An academic practice such as Yale Medicine values specific expertise, takes more time to consider the relevant history and symptoms, continuously learns about the newest trends in medicine, and applies the latest analysis technology and research. This extra care and consideration improves the value of a simple X-ray in the context of your overall health care.”