How does mri work

It took almost five hours to produce one image, and that original machine, named the "Indomitable," is now owned by the Smithsonian Institution. In just a few decades, the use of magnetic resonance imaging MRI scanners has grown tremendously. Doctors may order MRI scans to help diagnose multiple sclerosis, brain tumors, torn ligaments, tendonitis, cancer and strokes , to name just a few.

An MRI scan is the best way to see inside the human body without cutting it open. That may be little comfort to you when you're getting ready for an MRI exam. You're stripped of your jewelry and credit cards and asked detailed questions about all the metallic instruments you might have inside of you.

You're put on a tiny slab and pushed into a hole that hardly seems large enough for a person. You're subjected to loud noises, and you have to lie perfectly still, or they're going to do this to you all over again. And with each minute, you can't help but wonder what's happening to your body while it's in this machine.

Could it really be that this ordeal is truly better than another imaging technique, such as an X-ray or a CAT scan? What has Raymond Damadian wrought? MRI scanners vary in size and shape, and some newer models have a greater degree of openness around the sides.

Still, the basic design is the same, and the patient is pushed into a tube that's only about 24 inches 60 centimeters in diameter [source: Hornak ]. But what's in there? The biggest and most important component of an MRI system is the magnet.

There is a horizontal tube -- the same one the patient enters -- running through the magnet from front to back. This tube is known as the bore. But this isn't just any magnet -- we're dealing with an incredibly strong system here, one capable of producing a large, stable magnetic field. The strength of a magnet in an MRI system is rated using a unit of measure known as a tesla. The magnets in use today in MRI systems create a magnetic field of 0.

When you realize that the Earth's magnetic field measures 0. Most MRI systems use a superconducting magnet , which consists of many coils or windings of wire through which a current of electricity is passed, creating a magnetic field of up to 2. Maintaining such a large magnetic field requires a good deal of energy, which is accomplished by superconductivity , or reducing the resistance in the wires to almost zero. To do this, the wires are continually bathed in liquid helium at This cold is insulated by a vacuum.

While superconductive magnets are expensive, the strong magnetic field allows for the highest-quality imaging, and superconductivity keeps the system economical to operate.

Two other magnets are used in MRI systems to a much lesser extent. Resistive magnets are structurally like superconducting magnets, but they lack the liquid helium. This difference means they require a huge amount of electricity, making it prohibitively expensive to operate above a 0.

Permanent magnets have a constant magnetic field, but they're so heavy that it would be difficult to construct one that could sustain a large magnetic field.

There are also three gradient magnets inside the MRI machine. These magnets are much lower strength compared to the main magnetic field; they may range in strength from gauss to gauss. While the main magnet creates an intense, stable magnetic field around the patient, the gradient magnets create a variable field, which allows different parts of the body to be scanned. Another part of the MRI system is a set of coils that transmit radiofrequency waves into the patient's body.

There are different coils for different parts of the body: knees, shoulders, wrists, heads, necks and so on. These coils usually conform to the contour of the body part being imaged, or at least reside very close to it during the exam.

Other parts of the machine include a very powerful computer system and a patient table, which slides the patient into the bore. Whether the patient goes in head or feet first is determined by what part of the body needs examining.

Once the body part to be scanned is in the exact center, or isocenter , of the magnetic field, the scan can begin. MRI machines are evolving so that they're more patient-friendly. For example, many claustrophobic people simply can't stand the cramped confines, and the bore may not accommodate obese people.

There are more open scanners, which allow for greater space, but these machines have weaker magnetic fields, meaning it may be easier to miss abnormal tissue. Very small scanners for imaging specific body parts are also being developed. Other advancements are being made in the field of MRI.

This technique is safer and more comfortable for the patient as well as being less expensive than a traditional biopsy. Since MRE is able to recognize very slight differences in tissue density, there is the potential that it could also be used to detect cancer. New MRI just for Kids MRI is potentially one of the best imaging modalities for children since unlike CT, it does not have any ionizing radiation that could potentially be harmful.

However, one of the most difficult challenges that MRI technicians face is obtaining a clear image, especially when the patient is a child or has some kind of ailment that prevents them from staying still for extended periods of time. As a result, many young children require anesthesia, which increases the health risk for the patient. By creating a pediatric coil made specifically for smaller bodies, the image can be rendered more clearly and quickly and will demand less MR operator skill.

This will make MRIs cheaper, safer, and more available to children. The faster imaging and motion compensation could also potentially benefit adult patients as well. He is developing a motion correction system that could greatly improve image quality for MR exams. This improvement could reduce cost since less repeat MR exams will have to take place due to poor quality as well as make MRI a viable option for many patients who are unable to remain still for the exam and reduce the amount of anesthesia used for MR exams.

However, researchers funded by NIBIB have discovered a way to inject specialized compounds hyperpolarized carbon 13 into prostate cancer patients to measure the metabolic rate of a tumor. Monitoring disease progression can improve risk prediction, which is critical for prostate cancer patients who often adopt a wait and watch approach. How does MRI work? This sends out radio signals, which are picked up by receivers.

They also help to distinguish between the various types of tissue in the body, because the protons in different types of tissue realign at different speeds and produce distinct signals. In the same way that millions of pixels on a computer screen can create complex pictures, the signals from the millions of protons in the body are combined to create a detailed image of the inside of the body.

An MRI scan is a painless and safe procedure. You may find it uncomfortable if you have claustrophobia , but most people are able to manage it with support from the radiographer. Extensive research has been carried out into whether the magnetic fields and radio waves used during MRI scans could pose a risk to the human body. No evidence has been found to suggest there's a risk, which means MRI scans are one of the safest medical procedures available.

But MRI scans may not be recommended in certain situations. For example, if you have a metal implant fitted, such as a pacemaker or artificial joint, you may not be able to have an MRI scan. Read more about who can and can't have an MRI scan.