Imaging Used for Foot and Ankle Diagnosis

What is an MRI?

The acronym MRI stands for magnetic resonance imaging. This imaging technology uses a magnetic field and pulses of radio wave energy to create images of organs and structures inside of the body. An MRI can show problems within the body that can be difficult to see with other imaging techniques. The patient is placed within the MRI machine which contains a strong magnet. The images created by the MRI are then digitized into a computer which can be then analyzed by the doctor on a computer. Sometimes to enhance the images contrast dye is used.

The contrast dye is administered into the patient via an IV. The dye is used to enhance the image and add contrast to the pathology that is being identified. During the MRI there is no X-Ray radiation going through the body.

What is an MRI typically used for?

The MRI is typically used to visualize soft tissue abnormalities of the foot. Some doctors consider the MRI technology as a one stop shop for identifying both bone and soft tissue problems of the foot. Boney pathology is better seen with CT and Xray which will be discussed later in this article. Examples of pathology to be recognized with an MRI are Achilles tendon tears/ruptures, tendinitis, sprains, tumors, masses, stress fractures, and also bone infection.

This wide array of indications proves that the MRI can be very valuable when making a diagnosis.

Who cannot get an MRI?

Persons who are claustrophobic or afraid of confined spaces may have trouble with a traditional MRI. The creation of open MRIs has solved this problem and people who are fearful of small spaces can now be comfortable within the open MRI. People who have metal shards or have worked with small metal fragments may contain some in their eye and therefore are not going to risk having an MRI because this may cause damage to the eyes. Patient’s with metal clips from vascular procedures and also pacemakers will not be allowed to utilize the MRI either.

Essentially having metal in the body is a possible reason to not have an MRI completed due to the possibility of trauma to body.

What is a CT?

Computerized tomography scan or CT combines a series of X-ray images taken from different angles and then recreates a cross sectional image of the body. A CT provides more detail than an plain film X-ray because it shows multiple layers and provides more detail. A CT utilizes high levels of X-ray radiation and therefore should be limited in use. The less exposure to radiation the less likely to develop adverse reactions.

What is a CT used for?

The CT technology can visualize bones and structures with very good detail. The image slices created by the CT can be recreated into a 3d model of the foot and this can be used to analyze fracture patterns, specific tumor locations, boney deformities, and also dislocations of the bones. For a fracture that is in multiple pieces the CT can prove very helpful in surgical planning. This is because all the fragments can be visualized and therefore the repair can be planned out in detail.

What are the risks of a CT?

High radiation doses is a risk because this may cause cancer. This is why doctors will not subject patients to multiple CT scans unless medically warranted. For instance if someone was in a car accident and they suffered multiple injuries to the head, neck, spine, and extremities, then a CT scan of the body may be completed. This long exposure to the CT is medically necessary because the risk of not identifying the problems could lead to more harm to the patient. The benefit outweighs the risk and therefore the CT should be completed. If the patient is pregnant then high doses of radiation to a developing baby may cause damage to the unborn child and therefore the CT test would be avoided. If contrast dye is being utilized then an allergic reaction may occur in some patients. The patient will be treated accordingly if a reaction occurs with the proper medications.

What is an X-ray?

An x-ray is a quick way to produce images of the boney structures of the body. The beams of the x-rays are absorbed into the X-ray plate in different intensities. This is due to the different densities of the body which the beam travels through before absorbing into the plate. Bones are of the highest density and therefore appear white. Soft tissues such as tendons and ligaments are of various shades of gray depending on the density of the structure.

What is an X-ray used for?

To quickly identify fractures, dislocations, foreign bodies, and also infection. An office x-ray is a great way to diagnose a problem quickly without having to expose the patient to a CT scan or spend time getting an MRI. X-rays are also very cost effective and can be used to identify a wide variety of pathologies.

What are the risk of an X-ray?

A small dose of radiation is present during an X-ray but it is minimal. If a patient is pregnant then x-rays should be avoided because the risk of harming the unborn child is present and it is typically not worth the risk.

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