What are susceptibility artefacts?
Susceptibility artefacts are image disturbances that occur during certain imaging procedures such as magnetic resonance imaging (MRI), when different materials or tissue types with varying magnetic sensitivity (known as susceptibility) are present in the scanning area. This causes the resulting image to appear distorted or inaccurate in those areas.
How do these artefacts form?
MRI uses strong magnetic fields to produce detailed images of the inside of the body. Not all tissues or materials respond to this magnetic field in the same way. This becomes especially noticeable when metal objects are present in the body, such as dental fillings, implants, surgical clips, or foreign bodies from accidents. But natural differences, for example between bone and air in the sinuses or the digestive tract, can also produce these effects.
At the boundaries between materials with different magnetic properties, small disturbances occur in the magnetic field. This means that the image information in these areas can no longer be put together correctly. In the finished image, this appears as dark or bright patches, distorted structures, or blurry areas.
Where do susceptibility artefacts appear most often?
These image disturbances are especially noticeable in areas where metal meets tissue. After dental treatment, or where artificial joints or screws are present in bone, striking artefacts often appear. In the head area, artefacts can also form near the sinuses or the base of the skull, due to the air inside these cavities.
In some cases, even a tiny metal fragment, for example after a workplace accident involving the eye, can significantly affect the image. Even tattoos made with metallic inks can occasionally cause minimal artefacts.
What does this mean for reading the images?
Susceptibility artefacts can make it difficult, or sometimes impossible, to assess MRI images properly. When important areas of the body, such as the brain, spine, or joints, are affected by these artefacts, abnormal changes can sometimes not be identified with certainty. This may mean the scan needs to be repeated, or that additional methods such as a computed tomography (CT) scan are used.
For diagnosis, it is therefore important to understand how these artefacts form and to tell them apart from genuine abnormal changes. Radiologists are specially trained to recognise these differences and to improve image quality as much as possible.
Can susceptibility artefacts be avoided?
It is not always possible to prevent these image disturbances entirely. Before an MRI scan, you will always be asked whether you have any metal parts, implants, or other foreign bodies in your body. In some cases, the scan can be adjusted so that the problematic areas have as little influence as possible. Modern MRI machines and specialist scanning techniques also help to minimise the effects.
When metal parts are present in the body, alternative imaging methods are often recommended, or the scan is planned accordingly. Providing information about any known implants is also helpful, so that the radiology team can choose the best possible settings.
Why does this term matter in a medical report?
When a medical letter or report mentions susceptibility artefacts, it generally means that no reliable assessment was possible in certain areas of the image. This can explain why a particular area appears blurry or cannot be evaluated. This is not a disease or a worrying finding. It is simply a technical limitation of the imaging method.
If a report states that no reliable assessment was possible due to susceptibility artefacts, additional investigations may be suggested. This is a completely normal step and is no cause for concern. Often, a different imaging method is all that is needed to answer the outstanding question.
When should you speak to someone?
If you are unsure, for example whether an implant you have might affect the imaging, it is a good idea to mention this before the scan. After receiving a report, speaking with your treating doctor or radiologist can also help you understand what the susceptibility artefacts mean in your case. As a rule, these image disturbances are caused by technical factors and have no effect on your health.
Susceptibility artefacts are not a sign of illness. They are an indication of the limits of imaging technology. They occur mainly where different materials meet, and they can affect image quality. For further diagnostic work, suitable alternatives are usually available, so that a reliable medical assessment is still possible.
