MRI does not use ionising radiation. In situations where it will provide better or similar information to CT or X-ray, MRI may be a safer choice. This is particularly relevant for children and young adults, who are at a greater risk from ionising radiation than older adults.
To obtain a quality MRI scan, a patient must remain immobile for the duration of the scan and MRI scanning times are typically much longer than other modalities. This may mean that some patients will require sedation or anaesthesia for MRI. The risks of sedation or anaesthesia need to be balanced with the potential for a better health outcome with information obtained by MRI.
MRI is able to produce detailed (two- and three-dimensional) images of soft tissue, including of the brain, nerves, organs, cartilage, tendons, muscles and ligaments. This makes it a superior modality for imaging in some clinical situations.
However, the ability to see the components of the body in high detail does not necessarily mean improved outcomes for patients. GPs need to keep in mind whether any diagnostic imaging will alter treatment and the potential for revealing incidental findings.
The more sensitive the imaging modality, the more likely a finding of an ‘abnormality’. Many abnormalities are not clinically relevant and will not progress. Only a very small number of people will benefit from early detection of an ‘incidentaloma’, while others will suffer anxiety and the effects of investigations and treatment for something that would never have caused harm.5