- Last Updated on 14 December 2016
Magnetic Resonance Imaging (MRI) is a powerful diagnostic technique used to visualize organs and tissues within the body. The MRI scanner itself contains a large magnet which temporarily "aligns" water molecules. As various tissues in the body have different water content, an MRI scanner can differentiate these tissues and create an image. This is particularly useful when determining the structure of the brain, including the "gray matter", which is mostly brain cells, and "white matter", which is mostly connections between cells. MRI allows relatively easy detection of major structural abnormalities (e.g. tumors), developmental abnormalities (e.g. lissencephaly), as well as more common causes of pediatric epilepsy and infantile spasms, such as cortical dysplasia.
In comparison to other imaging modalities, MRI demonstrates exquisite resolution, and does involve the use of ionizing radiation (and its associated risks). However, MRI images require a patient to be nearly motionless for several minutes at a time, with a typical "epilepsy protocol" MRI requiring 30 minutes or longer, in total. As such, the vast majority of infants require sedation/anesthesia to remain still during this imaging procedure. Anesthesia entails its own risks, including allergic reactions, aspiration (the entry of saliva into the lungs, which can potentially cause serious infections), and others. These risks vary from patient to patient and are carefully evaluated by anesthesiologists and prescribing physicians.
Many types of metal (ferromagnetic metals and alloys) pose a safety hazard when using MRI. It is important to alert the MRI technologist if there is any metal or electronic device in your body: pacemaker, vagal nerve stimulator, cochlear implants, etc. Such metals might move under the influence of the magnetic field and/or produce dangerous amounts of heat.
Visually, the MRI scanner looks like a large tube. The procedure itself is painless, such that you do not feel the magnetic field. Among patients who do not receive sedation or anesthesia, remaining in the tube for an extended period can be psychologically uncomfortable (claustrophobia).
MRI studies often include a Magnetic Resonance Spectroscopy (MRS) examination.