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What is MRI?

The top section of this FAQ page is intended for veterinarians. For Pet Owner FAQ pages please see the Pet Owners section.

Magnetic Resonance Imaging (MRI) is a painless way to look inside the body without x-rays. It uses a powerful magnet, radiowaves and a computer to produce remarkably detailed images of internal tissues and organs. Because MRI can show problems that cannot be seen with other diagnostic imaging techniques, it has rapidly become the most powerful diagnostic imaging modality in human medicine. Up to now, high costs have limited its use in veterinary medicine but recently a group of veterinary radiologists and pathologists in the Portland/Vancouver area (VDIC) has purchased a MRI system.

A Very Sophisticated MRI System

VDIC has acquired a Philips Gyroscan T5-NT, one of the most sophisticated MRI system available in the world. This state-of-the-art MRI system can perform the most advanved MRI procedures to diagnose a wide variety of problems. The Gyroscan T5-NT was chosen because it produces images of exceptionally high resolution using the most advanced computer processing techniques. With the Gyroscan T5-NT, the veterinary patients in the Portland-Vancouver area now have access to the most sophisticated MRI equipment available.

How does MRI works?

Water makes up about 95% of living organisms, therefore hydrogen is the most common atom in our bodies. Like our planet, each hydrogen proton spins around a magnetic North pole and South pole. The North and South poles are normally oriented at random. When a patient is placed inside a strong magnetic field, however, the poles line up. This is the first stage of the process. Then the MRI system emits pulses of radio waves that knock the hydrogen protons out of alignment. Because the protons are still within the strong magnetic field, they rapidly return to alignment. In doing so, they release the energy they had absorbed, also in the form of radio waves. The returning radiowaves are detected by sensitive antennas called coils and a computer produces images showing the distribution and intensity of the radio waves emitted by the hydrogen protons. All protons do not release the same amount of energy at the same rate because they are influenced by surrounding atoms. Therefore different molecules will produce different MRI signals that can be used to differentiate tissues and abnormalities within tissues. This is why MRI can see certain types of tissues and lesions better than any other imaging technique: it displays information at the molecular level.

VDIC uses a Philips Gyroscan T5-NT, one of the most sophisticated MRI systems available in the world. This state-of-the-art MRI system can perform the most advanced MRI procedures to diagnose a wide variety of problems. The Gyroscan T5-NT was chosen because it produces images of exceptionally high resolution using the most advanced computer processing techniques. With the Gyroscan T5-NT, the veterinary patients in the Portland-Vancouver area now have access to the most sophisticated MRI equipment available.

Advantages of MRI compared to other imaging modalities?

The advantages of MRI compared to other diagnostic imaging modalities are numerous. MRI provides higher sensitivity for the detection of neurological disorders, musculoskeletal problems (occult lameness), ocular and nasal lesions, and for many types of cancer. It also provides sharp and clear images of soft tissues including the pancreas and adrenal glands. MRI is also valuable for cardiac studies and vascular studies including porto-systemic shunts without catheterisation or injection of contrast materials.

Because MRI is more expensive, many routine studies should still be performed with x-rays or ultrasound, but if additional information is needed or if the suspected lesions are within the brain, spinal cord, nasal cavities, or pelvic canal, MRI is often the best option. A final decision should be made by you, your veterinarian, and the radiologist. Table I lists the most important advantages of MRI.

Table I. Advantages of MRI.

  • No known harmful effects (no radiations)
  • No injection of contrast material around the spinal cord
  • Superior anatomic detail of soft tissues
  • Superior lesion visibility
  • Can detect edema and inflammation
  • Better evaluation of some areas of the brain
  • Better evaluation of blood vessels and blood flow
  • Can acquire images in any plane

Are there any risks with MRI studies?

MRI in itself is a very safe procedure. The magnetic field and the radio waves have no known harmful effects (MRI studies can even be performed during pregnancy). Because patients need to be absolutely still during an MRI study, however, general anesthesia is required for animals. To minimize risks associated with anesthesia, the renal, hepatic and cardiac status should be evaluated prior to MRI studies. Animals with cardiac pacemakers should not be scanned.

MRI and metallic objects

Ferro-magnetic metals can become dangerous flying objects in the strong magnetic field created by the MRI magnet. They may hurt people or the patient, damage the equipment or force us to inactivate the magnet (each occurrence costs $20,000). For security reasons, no one but the MRI technologists and radiologists are allowed in the MRI room.

Pets occasionally have internal metallic objects (bone plates, pins and wires used to repair fractures) or BB shots at various locations. These are rarely dangerous for the patient but they can cause large magnetic artifacts that make MRI studies useless. Therefore recent x-rays are required prior to MRI examinations to rule out the presence of metallic objects that could interfere with the study. These x-rays should be obtained by your veterinarian.

FAQ about MRI for Petowners

What will happen during my pet's MRI appointment?

You will be greeted by our receptionist and asked to fill out a consent form. Then a veterinary technician will check you in and explain the MRI procedure. Your pet will then be brought to our MRI suite and prepared for anesthesia. It takes approximately 1 1/2 hours to perform one MRI exam. Each additional exam takes 30-45 minutes longer.

Why can’t I be with my pet during the MRI exam?

Many pet owners believe their pet will be less stressed and more cooperative if they are with them, but it is often the opposite. It is also important to avoid interruptions and possible distractions to allow the radiologist, veterinary technicians and MRI technologist to fully concentrate on your pet and the MRI exam. MRI examinations can be performed more efficiently and more accurately when only trained staff is present. In addition, we use gas anesthesia in the ultrasound/MRI suite, making it illegal for untrained individuals to be present.

Why do we need anesthesia? What are the risks?

It is crucial for the patient to remain completely still during an MRI exam because any motion can blur the images. Therefore it is impossible to perform an MRI on an animal without anesthesia, unless the patient is comatose. What are the risks? Patients can have a life threatening reaction to anesthesia but this is extremely rare with modern anesthetics. While under anesthesia, patients are constantly monitored to detect and immediately address any change in their condition.


Why would my pet need a Cerebral Spinal Fluid Tap (CSF) after a brain or spine MRI? What are the risks?

When no obvious abnormalities are found or when more than one disease can have the same MRI appearance, a CSF tap (sampling and analysis of the fluid normally present around the brain and spinal cord) can provide useful information for the diagnosis and treatment of your pet’s condition. The procedure involves shaving a 2-3” square of fur at the base of the head and/or back area. The skin is cleaned with surgical soap and a needle is used to collect a small amount of fluid around the spinal cord. The fluid is sent for analysis. The results are faxed to your referring veterinarian within 24 hours. The risks are minimal and include possible infection, and (very rare) possible damage to the spinal cord.

Why would my pet need a biopsy?

MRI provides an excellent look inside the body but several diseases can have a similar appearance (e.g. tumors and abscesses). Determining the type of cells present within a lesion by obtaining a very small sample with a small needle allows us to make a final differentiation in most cases. We strongly recommend ultrasound-guided needle biopsies when we need to know the type of cells present to obtain a final diagnosis. If this is the case with your pet, the veterinary technician or radiologist will discuss it with you. A biopsy is never performed without your consent.

What is the biopsy procedure? Are there any risks? Will I have biopsy results today?

In most cases we shave the hair at the location of the biopsy, the skin is cleaned with surgical soap, and a small needle is inserted with ultrasound guidance into the area of concern. An average of four samples are taken to ensure that a diagnosis is obtained. The samples are transferred to a glass slide, prepared, and read by another specialist (cytopathologist). The biggest risk of needle biopsies is internal bleeding, but it is rare. If any significant bleeding is detected during the procedure, we will notify you and your referring veterinarian immediately. Fine-needle biopsy results are faxed to your referring veterinarian within 24 hours (except weekends). Please contact your referring veterinarian for biopsy results.

When will I get the results of the MRI?

Hundreds of images and a large amount of information are obtained during one MRI exam. Once the MRI exam is completed, a radiologist reviews the images to confirm that the study is complete and to determine whether a biopsy or CSF tap is indicated. All images are reviewed in detail a second time and the radiologist’s report is typed and faxed to your referring veterinarian within 24 hours. Please contact your referring veterinarian for the MRI results. We will send you home with a CD containing a copy of the entire MRI study. This CD should be given to your referring veterinarian to view the images collected.

What payment options do you offer?


We accept all major credit cards as well as cash and check. However, if you would like to spread your payments out, you can apply for CareCredit® which offers a 3 month same as cash option. For more details, click the link below or call our office.