Answers to Commonly Asked Questions About MRI

Why does my pet need CT or MRI?

Some areas of the body are difficult to image with conventional radiographs (X-rays) or ultrasound. Because of complex anatomy or overlying structures, tomographic (or slice) images must be used to evaluate the area. CT and MRI also both have the advantage of displaying images digitally, which can emphasize differences between normal and abnormal tissues making problems easier to detect, and the margins easier to recognize.

Is it safe?

Magnetic resonance imaging uses radio-frequency energy to excite molecules in your pet -- similar to that which a radio or TV station emits. No ionizing radiation is used. Low magnetic fields have not been demonstrated to be harmful to animals or people. Caution must be taken in animals or people that have been implanted with pacemakers or metal clips in certain areas. Because pets cannot move during the MRI scan, they must be anesthetized during the procedure. While there are some risks inherent to anesthesia, at VSCHV, anesthesia is supervised by board certified specialists who carefully assess each patient prior to the procedure. While CT scanning uses ionizing radiation, the dose received by the patient is similar to that of conventional radiographs (X-rays) and less than that for a human receiving a similar procedure. CT should be avoided in breeding animals during the first trimester of pregnancy. Pets are usually anesthetized for CT scans. These procedures are relatively quick (15 - 30 minutes), further minimizing the risks.

Why does my pet need to be anesthetized or sedated for the procedure?

Both CT and MRI require the patient to hold still during the scanning procedure. Even small movements result in artifacts which degrade the scan quality.

Why does the procedure cost more than conventional (radiographs) X-rays?

Equipment costs and maintenance costs are much higher for CT and MRI equipment. A CT scanner will cost 10 - 20 times as much as a conventional X-ray unit. An MRI unit costs 30 - 50 times as much.

How does MRI work?

When a patient is put in a strong magnet, some of the atoms become aligned with the magnetic field. If a carefully tuned radio-frequency (RF) pulse is sent into the patient, those atoms can be tipped over. As the atoms realign themselves with the magnetic field, they give off an RF pulse that can be detected by the MRI scanner. The amount of RF signal given off, and the time at which it is released are characteristic for certain tissues. RF signal changes can differentiate normal from abnormal tissues such as those affected by cancer, infection or trauma.

What are the indications for MRI?

MRI is useful for looking at soft tissue structures which have low contrast on conventional radiographs (x-rays) and complex soft tissue structures. The largest indications are in imaging the brain, spinal cord, and soft tissues of the musculoskeletal system.