What is an MRI?
Magnetic resonance imaging (MRI) is one of the most accurate methods of diagnostic imaging available today. MRI enables your physician to explore the human body without the use of ionizing radiation or invasive procedures to produce precise diagnostic information. A diagnostic procedure that uses a combination of a large magnet, radio frequencies and a computer to produce detailed images of organs and structures within the body, an MRI is often used to:
- Access blood flow
- Detect tumors and diagnose many forms of cancer
- Evaluate infections
- Assess injuries to bones and joints
- Examine the heart, brain, liver, pancreas, extremities, spine, male and female reproductive organs, and other soft tissues
How does an MRI scan work?
Performed on either an outpatient basis or part of inpatient care, an MRI scan is performed using an MRI machine, a large, cylindrical (tube-shaped) device that creates a strong magnetic field around the patient. Computers are then used to form 2-dimensional images of a body structure or organ based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. And unlike CT or x-ray studies, MRI does not employ radiation.
Is an MRI for everyone?
Certain medical conditions may prevent you from having a MRI. An exam cannot be performed if you have any of the following:
- Certain cardiac valves
- Aneurysm clips
- Certain inner ear implants or metal fragments in one or both eyes
How should I prepare for the procedure?
Most MRI exams do not have restrictions concerning eating and drinking. However, Houston Methodist Hospital staff will inform you, when you schedule your exam, of any required dietary restrictions.
Please inform your physician and the MRI staff before your exam if:
- You are breastfeeding, are pregnant, or think you might be pregnant.
- You require sedation or pain medication prior to your exam. You may take all of your usual medications, but you will need to notify Houston Methodist’s scheduling department and have a driver with you if are claustrophobic and require sedation.
What will I experience during the procedure?
Although every hospital has specific protocols in place, generally an MRI procedure follows this process:
- Upon arrival for your exam, you will be asked to fill out a safety questionnaire and remove all jewelry and metal objects such as hairpins and hearing aids. Because of the MRI’s strong magnetic field, no metal objects are allowed in the scan room. While patients are given a locker for their belongings, it is recommended you leave all valuables at home.
- You will also be asked to remove any eye makeup before your exam. Some makeup contains metal that may distort the images.
- You will be asked to change into a hospital gown.
- If a contrast medium is to be given intravenously (IV), an IV line will be started in your hand or arm. The IV line will be used to inject contrast at the appropriate time.
- A MRI technologist will assist you with your positioning on the padded exam table. You will be asked to lie as still as possible to avoid motion, which can cause blurred images.
- The MRI staff will have you in constant sight. Audio speakers inside the scanner will enable the staff to communicate with and hear you at all times. You will also have a call bell so that you can make the staff aware if you experience any problem during the MRI examination.
- During the scanning process, a loud knocking noise occurs. You will be given earplugs to wear to help block out the noise from the MRI scanner as well as headphones to hear any instructions given by the technologist.
- For abdominal, cardiac, and/or chest scans, you will be instructed to hold your breath for about 10-25 seconds (no longer than 30 seconds to avoid discomfort).
How long will the exam take?
A typical MRI exam will last 30 to 45 minutes depending on the specific exam requested by your physician.