What is Magnetic Resonance Imaging (MRI)?
An MRI is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
How does an MRI scan work?
The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. The magnetic field, along with a radiofrequency, alters the hydrogen atoms’ natural alignment in the body. Computers are then used to form a two-dimensional (2D) image of a body structure or organ based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, as do x-rays or computed tomography (CT scans).
A magnetic field is created and pulses of radio waves are sent from a scanner. The radio waves knock the nuclei of the atoms in your body out of their normal position. As the nuclei realign back into proper position, they send out radio signals. These signals are received by a computer that analyzes and converts them into an image of the part of the body being examined. This image appears on a viewing monitor. Some MRI machines look like narrow tunnels, while others are more open.
Magnetic resonance imaging (MRI) may be used instead of computed tomography (CT) in situations where organs or soft tissue are being studied, because bones do not obscure the images of organs and soft tissues, as they do in CT.
Due to the use of the strong magnet, MRI cannot be performed on patients with implanted pacemakers, intracranial aneurysm clips, cochlear implants, certain prosthetic devices, implanted drug infusion pumps, neurostimulators, bone-growth stimulators, certain intrauterine contraceptive devices, or any other type of iron-based metal implants. MRI is also contraindicated in the presence of internal metallic objects such as bullets or shrapnel, as well as surgical clips, pins, plates, screws, metal sutures, or wire mesh. Dyes used in tattoos may contain iron and potentially could heat up during an MRI, but this is a rare occurrence.