What Is an MRI Machine?

Magnetic Resonance Imaging (MRI) is a medical imaging technique that creates an image of the body's internal structure and function. It is most commonly used in radiology and provides a much clearer contrast between the body's soft tissues than CT scans do. An MRI is very useful in cardiovascular, neurological, oncological and musculoskeletal imaging. Unlike the CT, the MRI doesn't use ionizing radiation.

Body Composition

An MRI machine uses a powerful magnetic field to align the nuclear magnetization of protons in water in the body. Your body is mostly comprised of water molecules which contain two hydrogen nuclei or protons. The machine makes the protons align with the direction of the field.

Radio Energy

MRI machines emit radio wave energy which causes the hydrogen nuclei to make a rotating magnetic field. The machines pick up on this field and make pictures of structures and organs inside the body.

Electromagnetic Fields

During the scan, a second radio frequency (RF) electromagnetic field is turned on to cause the protons in your body to absorb some of its energy. When the RF is turned off, the protons release energy which is detected in an MRI.

Building Image

Additional magnetic fields are added during the scan to locate other protons, so the image can be built up. The technician does this by turning gradients coils on and off. This creates the knocking sounds you hear during an MRI.

Detecting Tissue

The MRI machine picks up the location of diseased tissue, such as tumors, because the protons vary from other tissues. When the technician changes the parameters on the scanner, there is contrast between different types of tissue.

Enhancements

To enhance the appearance of tumors, blood vessels, inflammation or other abnormalities, contrast agents can be injected into the patient's body through an IV.

Resources

• About MRIs