X-rays and other types of radiation
X-rays are a type of radiation. Radiation can also come from radioactive substances. There are lots of natural sources of radiation in the world, for example certain types of rocks, water and some of our food, including bananas, nuts and potatoes. Radiation also comes from space, but usually the atmosphere protects us, so this radiation mostly affects people who live on high mountains or travel in airplanes.
When we want to compare radiation doses, we use the quantity millisievert (abbreviated as mSv). In the UK, the average amount of radiation that people are exposed to each year is a little over 2 mSv. That means that over a lifetime, people could receive as much as 200 mSv of radiation exposure. The exact amount depends on where you live, what you do and how far you travel by airplane.
Why and how do we use X-rays?
X-rays can be the best way to find out what is wrong with someone or whether a condition has changed. If your doctor is sending you for an X-ray or scan, you can ask:
- what information do you hope to get from it?
- is it really necessary?
- is there an alternative that doesn’t use radiation that might be suitable instead?
You should mention if you have had any other X-rays or scans recently. The information from these might be useful too.
Different types of machine use X-rays in different ways.
- Radiography, which used to be called ‘plain film’, is the most common. This is what is used to look for broken bones, at your chest and lungs or your teeth. Radiographs are very quick, the X-rays are turned on for less than 1 second.
- Fluoroscopy, or screening, uses X-rays to produce moving pictures. These pictures might be used to guide a catheter through your blood vessels or look at the way special dye moves through your body. Screening takes between a few minutes and a few hours depending on how complicated the procedure is.
- CT or CAT scans use X-rays to provide very detailed pictures of the inside of the body. These can be examined slice by slice or reconstructed into a 3-D picture. Sometimes injections or drinks are used to make the pictures clearer. CT is quite quick. The X-rays are on for less than a minute, but you may need to spend time preparing before your scan.
X-rays and the law
Medical exposure to radiation is strictly controlled. In the UK, the Ionising Radiation (Medical Exposure) Regulations, also known as IRMER, set out the requirements for diagnosis and treatment. Each request for an X-ray or scan is assessed by an expert who makes sure that it is the most appropriate test for you. They may recommend a different test, if they think it would be more helpful. Whatever decision is made, your X-ray or scan will be done with the smallest amount of radiation that is necessary to produce the correct images.
There are five steps in the process:
- Request: Your doctor discusses your symptoms with you and decides to ask for an X-ray or scan to help with diagnosing the problem
- Justification: An X-ray expert (a radiologist or a radiographer) looks at the information that your doctor has sent and decides whether that is the best way to diagnose your condition
- X-ray: A radiologist or radiographer takes the X-ray
- Evaluation: A radiologist or radiographer studies the X-ray images. They look for anything that shouldn’t be there or any changes that might be the cause of your symptoms.
- Report: The radiologist or radiographer writes a report about your X-rays. This is then sent to your doctor.
Who are the people involved
Referrer: This is your doctor (or sometimes a nurse, physiotherapist or other healthcare professional) who has asked for the X-ray.
Radiologist: A doctor who specialises in X-rays and other types of medical images.
Radiographer: A healthcare professional who specialises in X-rays and other types of medical images.
Radiation Protection Adviser and Medical Physics Expert: A scientist who advises the hospital on the safest ways to use X-ray equipment.
You: It is important that you tell your doctor everything about your condition. Remind them if you have had a similar X-ray or scan in the past. Feel free to talk to any of the healthcare professionals involved, especially if something is happening that you were not expecting. For example, if you thought the X-ray was going to be of your left foot, but you have been asked to remove your right shoe.
Why do we have to think about X-ray safety?
X-ray radiation mostly passes through the body. That’s how the X-ray pictures are made. But sometimes the X-rays cause changes to the cells in our body. In almost all cases, these changes are repaired. Very rarely the repair doesn’t work properly and the cell starts to misbehave. Over a long time (many years, or even decades), this misbehaving cell can lead to a cancer. It is completely random. Although the risks are very small, we have no way of knowing when a repair might go wrong so to reduce the chances even further, we only use X-rays when they are necessary.
Because the changes caused by radiation take so long to show up, older people have an even smaller risk than younger people. That is why radiographers will ask patients if they might be pregnant and why extra care is taken when using X-rays on children.