Advanced Imaging: MRI

May 22, 2012
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Prior to now, we have discussed ways a doctor can get an image of your foot in the office. However, as we discussed, there are times when a more advanced and detailed image is needed. Magnetic Resonance Imaging (MRI) is a great tool to use in these situations.

In order to obtain an MRI, a patient is placed in a room with machine containing a giant magnet. This magnet causes the hydrogen ions in your bones, muscle, and other soft tissue to give off a signal that can be detected by a computer. Depending on the tissue, different signals will be given off. The computer analyzes the signals and develops a picture. Once the 1st picture is taken, the machine moves a couple millimeters and takes the next picture. If you can imagine slicing up a tomato or onion, an MRI is like slicing the foot into many individual sections. These individual slices are then grouped together so the doctor can get a good picture of the inside of the foot.

The major benefit to an MRI is that it can show bone, tendon, and cartilage in a very detailed image. This can be used by the doctor as a surgical planning tool before he takes a patient to the operating room. MRI can be helpful to diagnose a condition, but most problems can be diagnosed during a routine office visit without the help of an MRI. Although there are exceptions to that rule, an MRI is not usually ordered until the doctor and patient have agreed that surgical treatment is needed.

Another benefit to MRI is that no radiation is received by the patient, and it does not require a dye or contrast to be injected into the patient. MRI is a completely noninvasive imaging technique. For these reasons, MRIs are very safe for the patient.

On the other hand, an MRI requires you to lie motionless for an extended period of time. If you are moving when the slices are being taken, the image becomes distorted and impossible to interpret. This can be somewhat uncomfortable. In addition, if you have metal plates or screws in your body from previous surgery, the metal will distort the image, making it hard to see anything. For that reason, some patients may not be able to get a useful MRI. Lastly, MRIs are very expensive. Most insurance providers will not pay for an MRI until multiple conservative measures have been exhausted with no improvement in treating the patient.

MRI is a valuable tool that has helped doctors see subtle problems that x-ray and ultrasound miss. It is primarily a surgical planning tool to help surgeons be more prepared before surgery. However, it must be used appropriately so not as to waste resources.

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