Magnetic resonance imaging (MRI) is a non-invasive imaging technique used in hospitals and clinics to produce detailed soft tissue anatomical images through emission and absorption of energy of the radiofrequency range of the electromagnetic field by employing powerful magnets that produce a strong magnetic field around the area to be imaged without exposing the body to ionized radiation.
MRI is the most sensitive imaging test of the head, particularly of the brain. It is performed for either long-standing or abrupt onset symptoms, helping diagnose conditions such as brain infections, stroke, brain tumors, causes of seizures, developmental abnormalities, haemorrhage in trauma patients, multiple sclerosis, disorders of the pituitary gland and vascular problems such as aneurysms, arterial occlusions and venous thrombosis.
Whether or not to use a contrast-agent (mostly Gadolinium-based contrast-agents) depends on the nature of the disease/condition for which the scan is ordered. Most acute events (like acute headache, acute cerebrovascular accident [stroke] or transient ischemic attack, haemorrhages and concussions) do not require a contrast MRI. Some other conditions, including brain tumors, infections, seizures and multiple sclerosis do require the use of a contrast agent to differentiate diseased tissue from normal tissue.
Contrast MRI have a higher inherent risk than “simple” MRI. Since a contrast agent is used, there is the risk of an allergic reaction that could lead to anaphylactic shock (a serious allergic reaction). Nephrogenic systemic fibrosis is a rare complication of high doses of gadolinium-based contrast material used in patients with poor kidney function who undergo MRI. Mothers receiving a contrast MRI should not breastfeed their babies for 24 to 48 hours.