How does an MRI machine work?

Question

I mean if you look at the results it can look right through bone as if you sliced through a bone and are looking inside...it's pretty neet but I don't get how it works.

Answer 1

http://www.howstuffworks.com/mri1.htm
How does an MRI scanner work?

The patient lies inside a large, cylinder-shaped magnet. Radio waves 10,000 to 30,000 times stronger than the magnetic field of the earth are then sent through the body. This affects the body's atoms, forcing the nuclei into a different position. As they move back into place they send out radio waves of their own. The scanner picks up these signals and a computer turns them into a picture. These pictures are based on the location and strength of the incoming signals.

Our body consists mainly of water, and water contains hydrogen atoms. For this reason, the nucleus of the hydrogen atom is often used to create an MRI scan in the manner described above.

What does an MRI scan show?

Using an MRI scanner, it is possible to make pictures of almost all the tissue in the body. The tissue that has the least hydrogen atoms (such as bones) turns out dark, while the tissue that has many hydrogen atoms (such as fatty tissue) looks much brighter. By changing the timing of the radiowave pulses it is possible to gain information about the different types of tissues that are present.

An MRI scan is also able to provide clear pictures of parts of the body that are surrounded by bone tissue, so the technique is useful when examining the brain and spinal cord.

Because the MRI scan gives very detailed pictures it is the best technique when it comes to finding tumours (benign or malignant abnormal growths) in the brain. If a tumour is present the scan can also be used to find out if it has spread into nearby brain tissue.

The technique also allows us to focus on other details in the brain. For example, it makes it possible to see the strands of abnormal tissue that occur if someone has multiple sclerosis and it is possible to see changes occurring when there is bleeding in the brain, or find out if the brain tissue has suffered lack of oxygen after a stroke.

The MRI scan is also able to show both the heart and the large blood vessels in the surrounding tissue. This makes it possible to detect heart defects that have been building up since birth, as well as changes in the thickness of the muscles around the heart following a heart attack. The method can also be used to examine the joints, spine and sometimes the soft parts of your body such as the liver, kidneys and spleen.

How does an MRI scan differ from a CT scan?

With an MRI scan it is possible to take pictures from almost every angle, whereas a CT scan only shows pictures horizontally. There is no ionizing radiation (X-rays) involved in producing an MRI scan. MRI scans are generally more detailed, too. The difference between normal and abnormal tissue is often clearer on the MRI scan than on the CT scan.

How is an MRI scan performed?

The scan is usually done as an outpatient procedure, which means that the patient can go home after the test. During the scan it is important to lie completely still. For this reason it might be necessary to give a child an anaesthetic before they are tested.

Since you are exposed to a powerful magnetic field during the MRI scan, it is important not to wear jewellery or any other metal objects.

It is also important for the patient to inform medical staff if they use electrical appliances, such as a hearing aid or pacemaker, or have any metal in their body such as surgical clips, but orthopaedic metalware such as artificial hips or bone screws is not normally a problem.

Is an MRI scan dangerous?

There are no known dangers or side effects connected to an MRI scan. The test is not painful; you cannot feel it. Since radiation is not used, the procedure can be repeated without problems. There is a small theoretical risk to the foetus in the first 12 weeks of pregnancy, and therefore scans are not performed on pregnant women during this time.

Because patients have to lie inside a large cylinder while the scans are being made some people get claustrophobic during the test. Patients who are afraid this might happen should talk to the doctor beforehand, who may give them some medication to help them relax.

The machine also makes a banging noise while it is working, which might be unpleasant.

Answer 2

How Does An Mri Work

Answer 3

MRI = Magnetic Resonance Imaging. It basically applies a magnetic field to the body part then shoots radio waves at it. Knowing the frequency at which the hydrogens in water absorb this enegry allowes the operator to look at water in the body part. I guess this gives them info on injury to that body part. I'm a med chemist not an MD. This is very similar to an instrumet I use everyday NMR (Nuclear Magnetic Resonance). It alows me to determine the structure of a chemical.

Answer 4

Yes, because I hate to feel like I' am trapped and enclose. It sucks because you can't move and everything feels tight and scary kind of like a coffin. Try getting an Open MRI machine, it is much better because it is open and airy, not constricting at all. Your mom will be fine.

Answer 5

How MRI Works
To start, let's look at the parts of the MRI machine. The three basic components of the MRI machine are:

The primary magnet
The largest part of the MRI is the primary magnet. Developing a magnetic field of adequate strength to create MRI images was an early hurdle to overcome in the development of this technology. The gradient magnets
The gradient magnets are the 'fine-tuning' part of the MRI machine. They allow the MRI to focus on a specific part of the body. The gradient magnets are also responsible for the 'clanging' noise in a MRI.

The coil
Next to the part of your body being imaged is the coil. There are coils made for shoulders, knees, and other body parts. The coil will emit a radiofrequency that makes a MRI possible.
The Primary Magnet
A permanent magnet (like the kind you use on your refrigerator door) powerful enough to use in a MRI would be too costly to produce and too cumbersome to store. The other way to make a magnet is to coil electrical wire and run a current through the wire. This creates a magnetic field within the center of the coil. In order to create a strong enough magnetic field to perform MRI, the coils of wire must have no resistance; therefore they are bathed in liquid helium at a temperature 450 degrees Fahrenheit below zero! This allows the coils to develop magnetic fields of 1.5 to 3 Tesla (the strength of most medical MRIs), more than 20,000 times stronger than the earth's magnetic field.
The Gradient Magnets
There are three smaller magnets within a MRI machine called gradient magnets. These magnets are much smaller that the primary magnet (about 1/1000 as strong), but they allow the magnetic field to be altered very precisely. It is these gradient magnets that allow image "slices" of the body to be created. By altering the gradient magnets, the magnetic field can be specifically focused on a selected part of the body.
The Coil
MRI uses properties of hydrogen atoms to distinguish between different tissues within the human body. The human body is composed primarily of hydrogen atoms (63%), other common elements are oxygen (26%), carbon (9%), nitrogen (1%), and relatively small amounts of phosphorus, calcium, and sodium. MRI uses a property of atoms called "spin" to distinguish differences between tissues such as muscle, fat, and tendon.
With a patient in a MRI machine, and the magnet turned on, the nuclei of the hydrogen atoms tend to spin in one of two directions. These hydrogen atom nuclei can transition their spin orientation, or precess, to the opposite orientation. In order to spin the other direction, the coil emits a radiofrequency (RF) that causes this transition (the frequency of energy required to make this transition is specific, and called the Larmour Frequency).

The signal that is used in creating MRI images is derived from the energy released by molecules transitioning, or precessing, from their high-energy to their low-energy state. This exchange of energy between spin states is called resonance, and thus the name magnetic resonance imaging.

Putting It All Together...
The coil also functions to detect the energy given off by magnetic induction from the precessing of the atoms. A computer interprets the data, and creates images that display the different resonance characteristics of different tissue types. We see this as an image of shades of grey--some body tissues show up darker or lighter, all depending on the above processes.

Answer 6

The following link would definitely help you understand the complete functioning of an MRI machine.
Happy reading...