What does the equipment look like?
Most MRI machines consist of a large cylinder-shaped tube that is open on both ends and surrounded by a circular magnet. You lie down on a movable table that slides into the opening of the tube. A technologist monitors you from another room. You can talk with the person by microphone.
There is little preparation for an MRI exam. Take your daily medications as you normally would unless instructed otherwise. There are few dietary restrictions for an MRI. For those exams, you will be notified of the requirements.
A technologist will verify your identification and the requested exam. Your screening form will be reviewed by the technologist in consultation with the radiologist if indicated. If MRI contrast is indicated for the exam, an IV catheter will be inserted in your arm by a nurse or technologist.
MRI does not utilize ionizing radiation. Instead, radiofrequency pulses re-align hydrogen atoms that naturally exist within the body. This does not cause any chemical changes in the tissues. As the hydrogen atoms return to their usual alignment, they emit different amounts of energy depending on the type of body tissue they are in. The MR scanner captures this energy and creates a picture of the tissues scanned based on this information.
The magnetic field is produced by passing an electric current through wire coils in most MRI units. Other coils, located in the machine and in some cases, placed around the part of the body being imaged, send and receive radio waves, producing signals that are detected by the coils. The electric current does not come in contact with the patient.
A computer then processes the signals and generates a series of images, each of which shows a thin slice of the body. The images can then be studied from different angles by the interpreting radiologist.
Some MRI exams require an injection of intravenous MRI contrast. Inform the technologist if you experience any discomfort during the injection.