Magnetic Resonance Imaging (MRI)


What Does the MRI Unit Look Like?

The MRI unit looks like a large cube with a small hole in the center. This cube houses a powerful magnet. The patient is placed completely inside the MRI unit, actually in the middle of the magnet. MRI takes advantage of the many protons found at the atomic level in the body. To understand this technology, imagine these protons as spinning tops. These protons are all spinning in a random manner within the body. When your pet is placed in the magnetic field, all the protons in his body start spinning in a synchronized fashion. This spinning creates a low energy field. When the unit’s radio waves reach the animal, the protons move to a high energy level. Simply stated, the patient is absorbing energy in the form of radio waves. When the radio waves are turned off, the protons will release the energy they have absorbed, in the form of more radio waves. The MRI unit then recovers the radio waves emitted from the body and uses them to generate a computer image.

What Can an MRI Show in Dogs?

The technology of the MRI allows a veterinary radiologist to take a closer look at the inside of the patient’s head. An X-ray of the head shows only the bones of the skull. The contents of the head (that is the brain) remain hidden inside the skull. In other words, the bones of the skull cover the brain. A popular analogy to explain this concept is the “sliced bread analogy.” Without slicing the bread, you see only the oven-baked golden external surface. If we want to look at the white part of the bread we have to slice the bread and remove one of the pieces. A slice of bread is the equivalent of one MRI image. Taking this analogy further, thinner or thicker slices can be made and the bread can even be sliced in any orientation. This is a major advantage over CT.

At Tufts University School of Veterinary Medicine, MRI is now considered the standard technique to assess the brain and the spinal cord. During the last two years there has been an accelerated interest in making MRI more accessible to pet owners and the public is taking advantage of it. However, the best initial treatment for your dog is the treatment given by your family veterinarian. Despite wonderful imaging modalities such as MRI, a complete physical examinations and routine veterinary checkups is what will ensure the good health and long life of your dog.


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