An MRI is an imaging technology that provides doctors a snap shot of what is happening in the body of the dog. Certain tissue types cannot be evaluated clearly with other imaging technology. Soft tissue injuries can be hard to manage as they do not heal as quickly as do other tissues. An MRI can be a good way to evaluate the stage of recovery the dog is in. An MRI requires the dog to be medicated prior to the procedure, some animals will not tolerate this medication.
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MRI
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MRI or Magnetic Resonance Imaging provides a clear cross-section of the tissues in the body part being scanned in the dog. It works by detecting the alignment of the polarity of water molecules in the dog's body and then reading the different densities of the tissues. The machine then provides physicians with a clear view of the different tissues. This clear view allows doctors to detect minute abnormalities or anomalies in the tissue that may be the cause of the symptoms noted.
Soft Tissue
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Soft tissue of the dog typically refers to the connective tissue that supports the skeletal system. This includes muscles, tendons, ligaments and cartilage. Muscles work to contract and extend allowing the dog's limbs and other body parts to move. Tendons connect muscles to the bone and have less blood flow, or vasculature, in them than muscles. Ligaments hold bone to bone, typically over a joint and have even less vasculature. Cartilage provides a cushion to ease the friction of bone on bone movement in the joints. Cartilage has the least blood flow to it. Due to the poor vasculature in these tissues, when these areas are injured in the dog, healing can take months.
Why MRI
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Soft tissues do not readily show up on common imaging devices like X-rays. X-rays show bone well and the soft tissue attachments to the bone. Ultrasound will show the soft tissue well, but it is not as clear of an image, some small tears can be missed. Injuries such as cruciate ruptures may be symptomatic, as the dog is limping, but it is unclear the extent of the damage. In this case, the MRI can clearly show the extent of the damage however small it may be. Based on this clear view, the doctor can decide if surgery is necessary or could possibly wait.
Follow Up
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Performing an MRI is also sometimes the only way of reevaluating the extent of healing. For initial problems that were only detected by MRI, the MRI is the only way to see how the area is doing. For other patients who cruised through their procedure but are having problems in the recovery and rehabilitation phase, an MRI can give the physician a better idea of where the hold up is in healing. An MRI can also eliminate a physical problem as the cause of limping. If the MRI is clean, the problem may be psychosomatic for the dog.
Counter Indications
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An MRI must be performed on a completely still animal, or the image will not be clear. This typically requires the dog to be sedated or anesthetized completely to get the desired image. The medications involved in anesthesia can present a risk to some patients. The risk of anesthesia should be weighed against the benefit of the MRI.
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