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Magnetic resonance imaging

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Magnetic Resonance Imaging is a scan that takes images of certain parts of the body to spot problems with either tissues or other parts of the body like the back or shoulders by using a series of magnets and coils rather than radiation. It is one of the most safe scans for patients because of the fact there is no radiation and the most problems most have with the scan is that it is hard to stay still for a long period of time or claustrophobia, which is slowly disappearing due to developments to the traditional machine. Now there are other more recent machines that are open machines that can sit the patient up or however they would feel most comfortable and still get a clear image because of the stronger magnets used in the newer machine. After sitting or laying down for around 15-45 minutes, a radiologist will look at the images and try and identify the problem. There are many benefits to the MRI rather than risks, and the risks are very slim. The only way you can be in danger near the machine is if you have a metal object on you or inside you that may be affected by the magnet. Usually all that will happen is that the images will be unclear, but there is a slim chance it may be attracted to the magnet enough where it could move, therefore no electronics or metal is allowed in the room while the exam is taking place.

How MRI Works

An MRI machine at the U.S. Embassy in the Philippines

Unlike other exams like x-ray and CT, MRI does not depend on ionizing radiation. MRI uses radio waves to change the axes of spinning protons within a powerful magnetic field. The magnetic field is produced by the main magnet and passes through a series of wire coils either inside the machine or in certain cases, placed around the patient, and uses these coils to make and receive radio waves which produce certain signals. These signals come back through the coils and then are processed by a computer which reveals images taken of "thin slices" of the body or tissue being examined.

The radiologist will look at these photographs and determine whether there is a problem. MRI typically makes it easier for radiologists to spot the difference between diseased tissue and healthy tissue over other conventional imaging machines such as CT, Ultrasound, and x-ray. The procedure is performed by placing patient on a movable exam table and strapping them down to ensure the images are clear. Also, all metal and electronics must be out of the room so that it does not interfere with the magnets. Depending on the machine, coils may be placed around the patient for the sending and receiving of the radio waves. The patient will be moved inside the magnet and have a series of images taken and depending on the machine and type of examination, the time usually varies from 15-45 minutes.

When patients are in the midst of the exam, the most common complaint or difficulty they experienced has been that they find it difficult to stay still, or they feel like they are trapped inside, commonly known as claustrophobia. Because of the clear images produced by a successful exam, MRI is typically more expensive than other exams and can take more time. Overall MRI is one of the most safe and reliable scans out and poses almost no risk to the patient with possibly huge benefits[1].

Types of MRI

There are several different ways MRI can be performed. For the most part they operate the same way but some can have the patient change positions for their exam. The ways below are several ways the scan can be administered.

Upright MRI- This is a certain type of MRI machine that can adjust the position of the patient to gain a better image of the area being looked at. This can be used to look at vertebrae and other lower back problems. The patient can be placed in either a standing sitting, or recumbent position, whichever suits their needs the best. This is considered a true "open" MRI, which means patients are not lying down surrounded on all sides by the magnet, and are rather just in the open. For any people who are claustrophobic, or just have a hard time staying still, this is definitely the easiest and most convenient type of MRI, rather than the traditional machine.

High Field- Basically, the high field MRI is a type of MRI machine that allows for higher quality images because the magnet has a higher field, hence the name "high field". Most MRI machines are considered low field at .3 Tesla. These high field machines have a .6 Tesla, which provides much clearer images. The high field machines are generally Open MRI or Upright MRI machines because they normally are newer than the closed machines[2].

References

  1. RSNA and ACR http://www.radiologyinfo.org/en/info.cfm?pg=bodymr#part_five RadiologyInfo.org, Web, August 19th, 2011.
  2. Upright Imaging and Diagnostic, http://uprightimagingmri.com/ Web, UprightImagingMRI.com, 2008

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