Tuesday, May 22, 2012

Advanced Imaging: MRI


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.

Tuesday, May 8, 2012

Podiatric Ultrasound


I’m sure many of you hear the word “ultrasound” and correlate it with pregnancy and gynecology, but ultrasound is a very safe and useful tool podiatrists have to visualize and diagnose the source of a patient’s pain.  Let’s discuss some of the pros and cons of ultrasound.

First and foremost, ultrasound is very safe to the patient.  Ultrasound is simply a machine that sends out sound waves at a certain frequency, which then forms an image from how the waves bounce back.  Most importantly, no radiation or tissue damage occurs from these sound waves.  This is supported by multiple studies and its long and continued use in visualizing babies in utero.  This long history of safety has led to the development of ultrasound machines specifically made to see bone, tendon, and ligament.

Secondly, ultrasound gives a real-time image.  X-rays, MRI, and CT scans are frozen images.  Ultrasound gives a “living image” so that as the patient moves the foot, the image reflects that movement.  This gives the doctor more information on how the foot is functioning as it moves.  Without this insight, the doctor might miss the true source of the pain.  Ultrasound can be used to visualize bone as well as soft tissue.  In addition, when giving an injection, the doctor can give it under the guidance of ultrasound.  This can help the doctor insure that the medicine is being placed in the area of inflammation.

Lastly, ultrasound is inexpensive and convenient.  Ultrasound machines for foot and ankle imaging are very small and can be moved from exam room to exam room very easily.  When compared to CT scans and MRI, ultrasound is much cheaper and therefore, insurances are more likely to cover the cost.  Ultrasound does not require a dye to be injected into your veins (often needed for CT scans), neither does it require you to lie motionless (as is needed with MRI).  All in all, is a very cost effective way to diagnose foot and ankle conditions.

The main disadvantage to ultrasound is that it requires a trained eye to both know the mechanics of the machine and to read the ultrasound image.  Only after much experience can a technician consistently read an ultrasound accurately.  Your podiatrist will be able to correctly interpret your ultrasound.

Now that we have covered the ways to image the foot and ankle in the office, we will discuss the more advanced imaging techniques of CT scans and MRIs in our next posts.