A magnetic resonance imaging (MRI) scan is a common procedure used by hospitals around the world. MRI uses a strong magnetic field and radio waves to create detailed images of the organs and tissues within the body.
The development of MRI revolutionized the medical world. Since its discovery, doctors and researchers have refined techniques so as to use MRI scans to not only assist in medical procedures but also aid in research.
Contents of this article:
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on MRI scanners
Here are some key points about MRI scanners. More detail and supporting information is in the main article.
- MRI scans are a non-invasive and painless procedure
- Unlike X-rays and CT scans, MRI does not use ionizing radiation (which is potentially harmful to the patient)
- MRI is an acronym for magnetic resonance imaging
- Raymond Damadian created the first MRI full body scanner, which he nicknamed the "Indomitable." It is currently on display at the Smithsonian Institution
- The magnets used in an MRI scan need to be constantly cooled to a temperature of absolute zero (-459.67°F)
- Liquid helium is traditionally used to cool the magnets
- An upright MRI scanner has now been created, enabling patients to feel less claustrophobic
- The cost of an MRI scanner starts at $150,000
- Japan has the most MRI scanners, with 46.5 per one million citizens.
What is an MRI scan?
An MRI scan uses a large magnet, radio waves, and a computer to create a detailed cross-sectional image of the patient's internal organs and structures.
The scanner itself typically resembles a large tube with a table in the middle, allowing the patient to slide into the tunnel.
An MRI scan differs from CT scans and X-rays because it does not use ionizing radiation that can be potentially harmful to a patient.1
Background of the MRI scanner
The first full-body MRI scanner was created by Prof. Raymond Damadian in 1977 and took nearly 5 hours to produce the first ever full body scan of a human. Dr. Ramadan nicknamed the first MRI scanner the "Indomitable" and it is currently housed in the Smithsonian Institute.2
The idea for MRI was initially conceived by Damadian in 1971 after he recognized that under nuclear magnetic resonance certain mouse tumors would display elevated relaxation times compared with normal tissues in vitro.
How does an MRI scan work?
An MRI scanner can be found in most hospitals and is an important tool to analyze body tissues.
An MRI scanner contains two powerful magnets, which represent the most critical part of the equipment.
The human body is largely made of water molecules, which are comprised of hydrogen and oxygen atoms. At the center of each atom lies an even smaller particle called a proton, which serves as a magnet and is sensitive to any magnetic field.
Normally the water molecules in our bodies are randomly arranged, but upon entering an MRI scanner, the first magnet causes the body's water molecules to align in one direction, either north or south.
The second magnetic field is then turned on and off in a series of quick pulses, causing each hydrogen atom to alter its alignment and then quickly switch back to its original relaxed state when switched off. The magnetic field is created by passing electricity through gradient coils, which also causes the coils to vibrate, resulting in a knocking sound inside the scanner.
Although the patient cannot feel these changes, the scanner can detect them and, in conjunction with a computer, can create a detailed cross-sectional image for the radiologist to interpret.
What are MRI scans used for?
The development of the MRI scan represents a huge milestone for the medical world, as doctors, scientists and researchers are now able to examine the insides of the human body accurately using a non-invasive tool.
The following are just some of the examples where an MRI scan is used:
- Abnormalities of the brain and spinal cord
- Tumors, cysts, and other abnormalities in various parts of the body
- Injuries or abnormalities of the joints, such as back pain
- Certain types of heart problems
- Diseases of the liver and other abdominal organs
- Causes of pelvic pain in women (e.g. fibroids, endometriosis)
- Suspected uterine abnormalities in women undergoing evaluation for infertility.
On the next page, we look at what happens before, during and after an MRI scan. We also address some of the most frequently asked questions about MRI scans.