Radiation Risks

What is the risk?

Imaging in medicine is well established and widely accepted with many benefits. We want to provide you with the information you need to make the right decision for you.

This section page looks at the risks of medical imaging such as Dental X-rays, X-rays, CT, Nuclear Medicine, PET/CT, DXA, Fluoroscopy, Interventional Radiology and Cardiac Catheter interventions. The risks of MRI and ultrasound are slightly different and not covered here.

This page gives more detail around radiation risks. It is recommended that the 'Types of Imaging' section is viewed before this more detailed information.

The main risk associated with imaging is cancer later in life. Different exams are related to different levels of risk from cancer. Other risks include skin reddening and cataracts later in life. These effects are associated with specific exams and will be discussed with you where they may be an issue. More information on these risks are discussed below.

The exam that is best for you will change depending on the information that is required. Everyone that is involved in your diagnosis and treatment works together to keep the dose and risk as low as possible to get the information that they need.

This video explains the types of risks connected with imaging exams and tries to put these risks into perspective.

The risks at the doses involved in medical imaging are so low that scientists aren't sure that they exist. This is because the natural risk of cancer is much higher than the risk from imaging and because so many things affect the risk of cancer.

To be on the safe side we assume that the effects seen at high doses also happen at lower doses but at lower levels.

We use this model to predict levels of risk that we cannot measure. However, we know that the risks cannot be much higher than predicted as then we would be able to measure them.

The image shows a linear relationship between the risk of cancer and the amount of radiation an individual is exposed to. This can be measured at high doses but the area on the graph associated with low dose diagnostic exams is less certain. Therefore, the linear relationship is assumed to continue to low doses.

Variation in risk with age

The natural risk of cancer is affected by things such as where we live, our age, what we eat, how much exercise we get etc. In the same way the risk of cancer from radiation exposure is affected by things like age. The older you are the lower the risk is from radiation.

Risk overview

Below is a diagram that broadly shows the risks for each type of imaging. The bands are wide because risk changes so much depending on the exam and individual exposed. For Fluoroscopy, Interventional Radiology and Cardiac Catheter lab exams the risks will be discussed with your prior to the exam. If you would like these risks expressed in another format you can find this in the Risks in Perspective section.

This image shows wide risk bands associated with different types of exam. Dental X-rays are associated with a negligible to minimal risk (less than 0.001%), X-rays are associated with a negligible to very low risk (less than 0.01%). CTs are associated with a very low to low risk (between 0.01 and 0.1%). Fluoroscopy is associated with a very low to low risk (0.01% to 0.1%). Interventional radiology and cardiac catheter labs are associated with a very low to moderate risk (0.01-1%). Nuclear Medicine is associated with a wide band of risk from negligible (0.0001%) to low risk (0.1%). PET/CT is associated with a very low to low risk (0.01-0.1%). Low dose (lower risk) procedures are often simpler and produce less information than high dose, complex procedures.

Figure 1. Diagram of the typical levels of risk associated with each type of exam.

If you would like more risk information you can obtain it at the link below.

Hereditary defects

Hereditary defects in the children or grandchildren of individuals have not been proven in humans. Potential hereditary defects include malformations, metabolic disorders and immune deficiencies. It is important to note that these effects can only occur if the individual has not yet had their children. The risks are lower than the cancer risks that the individual is exposed to.

However, these effects have been seen in animal populations and the potential risks are displayed below for a selected exam (Taken from UK Health Security Agency data):

Repeated Exposures

Almost all medical treatment or diagnosis are associated with some risk. This includes imaging. However, the benefit to you will be that the images will be used to inform your treatment. You can find out about the risk of imaging here. Sometimes people will need to have repeated medical imaging during their lifetime.

When your referral is received, a healthcare professional will look at the risks and the benefits of the scan. They will review past imaging for any information in a process called justifying. The risk to you will always be minimised regardless of the number of exams that you have had.

The additional risk of cancer due to each exam that you have does not depend on earlier exams. So, if you have a chest x-ray today the additional risk from that x-ray would be the same if you had 10 x-rays in the past or if you had none. Below is a video which explains this in more detail.

Individuals who have repeated head CTs may be at increased risk of cataracts later in life. The imaging specialist who will justify your exam will take this into account.

The risk of erythema (skin burn like sunburn) may be increased if you have multiple long and complex fluoroscopy exams within a short period of time. The staff member justifying your exam will check if this is the case and discuss this risk with you prior to the exam. The alternative to these procedures is usually open surgery which is associated with other risks.

If you are at all concerned about your history of exposure, please discuss this with your doctor.

Take away points

  • Your referrer and the imaging specialist will work to reduce the risk to you from any exposure.

  • They will look at any factors which may affect the risk benefit balance for an exam, such as results from previous exams.

  • This ensures that the risk to you over multiple exposures is minimised as the risk benefit analysis carried out has as much information as possible.

  • Longer, more complex or higher skin dose exams can lead to skin reddening similar to sunburn.

  • If you are pregnant, trying to get pregnant or breastfeeding please tell your healthcare professional before having an imaging test.

  • Contact your healthcare professional to discuss further if you feel anxious.

Skin Burns

Some exams may lead to high skin doses that can lead to skin reddening (erythema), like sunburn. This effect is usually limited to long, complex interventional fluoroscopy or cardiology exams. The alternative to these interventions is usually open surgery which lead to other risks.

If you are having an exam which could lead to this effect, you will be informed of the risk prior to exposure. This effect is very rare. If you are exposed again within a short period of time, it may make it more likely that you see any reddening.

Throughout your procedure, the Radiographer and the doctor will be aware of the radiation dose that you are receiving. They will make sure that the dose is as low as possible and should inform you after the exam if they think that you may be at risk of showing skin burn. The skin burn may not appear for a number of weeks. You will be given information on what to do if this happens. However, some simple steps you can take that may ease the burn are:

  • Apply a moisturiser to the reddened area two times a day. Such as E45 cream.

  • Take a bath or shower every day if possible, using baby soap or unperfumed soap or unperfumed shower gel.

  • Pat the area dry with a soft towel, being very gentle with folds of skin, taking care not to rub.

  • Do not swim if you have visibly red skin.

  • Do not use a sun bed.

If you are concerned about this effect, please discuss it with your doctor during the consent procedure.


Cataracts are when the lens, a small transparent disc inside your eye, develops cloudy patches. Over time these patches usually become bigger causing blurry, misty vision and eventually blindness.

While radiation can be attributed to an increased risk of cataracts, all medical imaging will be optimised to ensure the radiation used is as low as reasonably practicable.

Risk is mainly prominent through direct exposure of radiation to the eye. For example a head CT will be usually be tilted to avoid direct exposure of the eye where possible.

Cataracts are relatively easily rectified using a surgery with a high success rate. The surgery involves replacing the cloudy lens inside your eye with an artificial one. This involves an approximately 2 to 6 week recovery period.


ICRP: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5228042/

What to discuss with your healthcare provider

How people feel about risks depends on the individual. A risk that is acceptable to one person may not be acceptable to another. For example, one person may feel that the risk of taking part in a parachute jump is worth it because of the enjoyment that they get from it, whereas another person may not feel that this is worth the risk.

Your doctor will discuss your situation with you. To get the best out of discussions with your doctor sometimes it is a good idea to plan ahead the sort of questions that you want to ask. Christer Mjåset (neurosurgeon) has suggested 4 questions to help you:

  1. Is this really necessary?

  2. What are the risks?

  3. Are there other options?

  4. What happens if I don't do anything?

If you would like more information the Royal College of Obstetricians has produced some helpful guidance on risk and making the best decision for you.

Although the added risk for diagnostic procedures is small, you should let your referrer know of any past scans you have had that you think might already contain the information that they need.

If you might be pregnant, please let your referrer and radiographer know.

For more information about medical imaging with regards to pregnancy, please see below.


Most of the time when you have an X-ray during pregnancy the risks to both you and your baby are very low. If the X-ray is above the diaphragm or below the knees the risk with modern equipment is so low that we will not ask you about your pregnancy status.

If it is between these positions, we will ask every individual of childbearing potential and between the ages of 10 and 55 whether they could be pregnant.

If you answer that you are or suspect that you are, a clinician will take into account the risks to you and the baby of not having the exam and potentially not getting the right diagnosis against the radiation risks and will help you to decide if it is still the right exam.

If you answer that you are unsure whether you are pregnant depending on the risk the following actions may be taken:

  • Wait until we are sure if you are pregnant or you are at point in your menstrual cycle that means that the risk is low;

  • Taking a pregnancy test;

  • Carry on with the exam as the potential risk is still less than the risk of not carrying out the exam (it is justified).

Take away points

  • If you are pregnant, trying to get pregnant or breastfeeding please tell your healthcare professional before having an imaging test.

  • If the exposure is outside of the area between your diaphragm and knees the risk is very low and the exam can go ahead.

  • If the imaging is between the diaphragm and the knee, they will discuss with you whether this is the best test for you.

  • A doctor specialising in imaging in medicine (Radiologist) or specially trained Radiographer will review the request and ensure that it is the right test for you.

  • If it is decided that the imaging is needed the Radiographer will use their training and experience to minimize the dose to the baby.

  • If you find out that you are pregnant after an exam, the risk is likely to be low.

  • Contact your healthcare professional to discuss further if you feel anxious.

  • There are no diagnostic exams that will lead to a level of risk that would mean that you need to think about termination of the pregnancy based on the clinical risk.

The Royal College of Radiologists has provided risk guidance for pregnancy procedures and risk estimates.

Some people like to have detailed numerical information about risks. We have provided a summary of the numerical risks provided by the Royal College of Radiologists here. If you want to put these risks into perspective or see them presented in another format click here. However, if you require more detail or advice please contact your local Radiology department.