X-ray test: what to expect, how safe it is and when it is used

1. Introduction

An X-ray is an imaging test that uses a small amount of radiation to show the inside of the body ^[1]. The pictures are called radiographs ^[4]. Most X-rays are done in hospitals, and dental X-rays are usually done in dental surgeries ^[1]. This article explains what an X-ray can show, how to get ready, what happens during the test and what to know about safety. Your doctor decides whether you need an X-ray and what the result means.

2. How an X-ray works

X-rays are a form of radiation with more energy than visible light, and they can pass through the body ^[4]. Different tissues absorb different amounts. Bone absorbs the most and looks white on the picture. Fat and soft tissue look grey, and air-filled areas such as the lungs look black ^[2]. A radiologist, the person who reviews the images, shares the findings with your provider ^[2].

3. What X-rays are used for

According to the NHS and MedlinePlus, X-rays can image bones, teeth, lungs and the digestive system. They may be used to ^{[1, 2, 4]}:

• Check for broken bones after an injury.
• Look for tooth decay.
• Look for signs of lung infection such as pneumonia on a chest X-ray.
• Investigate symptoms that could be caused by an infection or a blockage in the digestive system.
• Check whether a child has swallowed something harmful, such as a battery.
• Help doctors see inside the body during a procedure.

There are also related tests that use X-rays. A mammogram is an X-ray of the breast used to look for breast cancer ^{[2, 4]}. A bone density scan (DEXA) measures bone strength. A CT scan uses X-rays and a computer to make more detailed images ^{[1, 4]}. Other tests use contrast dye or barium, which you drink, to look at blood vessels or the digestive system ^[1].

4. Getting ready

For many X-rays you need little or no preparation ^[2]. You will be told in advance if you need to prepare. This may include removing metal items such as jewellery, zips, bras and hair clips, fasting for several hours, or taking a laxative the day before for certain scans ^[1]. You may be asked to wear a lead apron to protect certain parts of your body ^[2].

Tell the staff if you are pregnant or might be, are breastfeeding, take medicines, or have allergies or past reactions to barium or contrast dye ^[1]. You can also ask for a chaperone, who can be someone you know or a trained member of staff ^[1].

5. What happens during the test

A radiographer carries out the X-ray ^[1]. You may need to change into a gown, then stand, sit or lie in a certain position and hold still for a moment while the picture is taken ^{[1, 2]}. The scan itself takes only a few minutes, and you will not feel anything during the exposure ^[1].

If contrast dye or barium is used, you may feel warmth, flushing or a metallic taste for a short time. You may be asked to wait up to 30 minutes afterwards so staff can check for a reaction ^[1]. After a standard X-ray you can usually go home and return to normal activities straight away ^{[1, 2]}.

6. Results

You should be told when to expect results. They may be ready the same day, or you may have an appointment a few weeks later ^[1]. A health professional explains what the images show and what the next steps are. These may include more tests ^[1]. If you have not heard anything after a few weeks, contact the doctor who referred you ^[1].

7. Safety, radiation and pregnancy

X-rays use ionizing radiation, a type of energy that can damage living cells. The main concern is a small increase in lifetime cancer risk, which depends on the dose, your age and sex, and the part of the body imaged. Very high exposures, which are not used in ordinary tests, can cause skin burns or cataracts ^{[3, 4]}. The risk is higher in younger people ^{[3, 4]}.

The NHS describes X-rays as usually very safe, with serious complications being rare, and says doctors weigh the risks against the benefits before recommending one ^[1]. MedlinePlus compares the dose of a chest X-ray to roughly 10 days of natural background radiation from the environment ^[2]. The FDA says the benefit of a clinically appropriate X-ray generally outweighs its risk, and that the lowest dose that gives a usable image should be used ^[3].

The FDA suggests questions you can ask your provider ^[3]:

• Is this exam necessary?
• Are there options that do not use radiation?
• Does this facility use dose-reduction methods and is it accredited?
• Should I keep a record of my imaging history?

Children, pregnant patients and people having screening with no symptoms need extra consideration ^[3]. Always tell staff if you are or might be pregnant ^{[1, 2, 3]}.

8. When to see a doctor

Talk to a doctor if you have an injury with severe pain or a limb that looks out of shape, a cough or chest symptoms that do not settle, or other symptoms that your doctor might want to look into with imaging. After an X-ray, contact the doctor who referred you if you have not heard about your results after a few weeks ^[1]. If you had barium or contrast dye and develop a rash, dizziness or difficulty breathing, tell staff straight away ^{[1, 3]}.

In an emergency, call your local emergency number (112 in India, 911 in the United States).

9. Conclusion

An X-ray is a fast, painless test that is useful for bones, teeth, the chest and other areas. It uses a small amount of radiation, and doctors choose to use it when the benefit is greater than the small risk. Tell staff about pregnancy, medicines and allergies, keep a record of your scans, and ask your doctor any questions about why the test is needed.