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Understanding Veterinary Imaging: CT scans, MRIs, & X-rays Explained

Diagnostic imaging is a standard part of routine and emergency veterinary care. But how are each of the tools different? Here, our Santa Barbara vets discuss what you can expect when you bring your cat or dog in for a CT scan, MRI, or X-ray imaging at our veterinary diagnostic lab.

CT Scans vs. MRIs vs. X-Ray vs. Pet Scans

Diagnostic imaging is a vital part of veterinary care. It provides information about the internal functions to make diagnosis and treatment quicker and easier. So, what should you know about X-rays vs. PET scans vs. CT scans vs. MRIs?

X-rays are one of the most useful and widely used tools in veterinary medicine. X-rays can give your veterinarian an image of your pet's bones, tissues, and internal organs. X-rays are non-invasive, painless, and safe for dogs and cats. X-rays, especially digital X-rays, use extremely low doses of radiation.

Also known as a CT or CAT scan, computed tomographic imaging uses radiation (X-rays) and a computer to capture multiple individual images or 'slices' throughout a region of interest in the body. 

A CT scanner's image can be compared to one slice of bread that's part of an entire loaf. The CT machine produces two-dimensional slices of a section of your pet's anatomy and then reconfigures them to a complete image that a vet can see. 

These slices can also be used to create three-dimensional reconstructions that can help plan surgeries. Once the images are produced, your veterinarian can review and interpret them. 

MRI (magnetic resonance imaging) scans can provide your veterinarian with detailed, high-resolution images of your cat or dog's soft tissues, such as the brain, spinal cord, tendons, ligaments, and abdominal organs.

While we aren't discussing them today, you may have heard the term PET scan. A PET scan is slightly different from a CT scan as it shows doctors how the body's tissues work on a cellular level. This is done by injecting a material known as radiotracers, which glow on the images.

What can dog or cat CT scans, MRIs, and X-rays help vets diagnose?

Frequently used in both human and veterinary healthcare, these diagnostic tools diagnose different conditions or illnesses depending on an animal's needs.


X-rays for dogs are an extremely useful diagnostic tool. A wealth of information can be obtained. Your vet may recommend an X-ray based on potential underlying health issues in your dog, including:

  • Trauma
  • Tumors / Cancer
  • Foreign objects, including GI obstruction
  • Fractured bones
  • Heart disease
  • Pneumonia, bronchitis, asthma
  • Fluid within the abdomen or chest
  • Bladder stones
  • Organ enlargement
  • Muscle, joint, or ligament tears; arthritis; hip dysplasia
  • Pregnancy
  • Dental diseases
  • Determining if surgery is necessary

CT Scans

A CT machine produces high-resolution images, which allows for a detailed evaluation of your pet's anatomy that would not be possible with standard X-rays.

CT scanners provide a clear view of your pet's soft and bony structures, including the spine, nasal cavity, musculoskeletal system, thorax, and extra-thoracic structures. They can be used to evaluate: 

  • Nasal disease
  • Lung cancer 
  • The extent of canine and feline cancers
  • Ear disease
  • Pulmonary pathology 
  • Vascular abnormalities
  • Musculoskeletal and bone disorders, such as fractures or bone tumors 

CT scans can be used to help plan and facilitate surgery and minimize surgery time, which is important for pulmonary and liver tumors. 


Veterinary MRIs can produce a more detailed image of your pet's body than other diagnostic imaging tools, such as X-rays or CT scans, for many types of soft tissue injuries or diseases. An MRI may be useful in these situations:

  • To better visualize internal organ abnormalities
  • To identify issues with the brain and spine (brain tumor or inflammation, spinal disc tumor, herniated discs, stenosis)
  • Examination of the nasal cavity, sinuses, and ears 
  • To diagnose musculoskeletal diseases and injuries (e.g., shoulder instability, ruptured cranial cruciate ligament) 
  • In cases where a simple X-ray did not reveal enough information to make a diagnosis

MRIs typically take 45 minutes to an hour to complete and can provide critical diagnostic information about your pet's condition. 

How can I prepare for my dog or cat's CT Scan, MRI, or X-ray appointment?

CT scans or X-rays are often performed when a cat or dog is brought in for an appointment with one of our veterinarians. No preparation is required for these.

Preparation instructions for an MRI may vary depending on what the vet is looking for. There may be fasting requirements for which you'll need to withhold food for a specific number of hours. You may also need to restrict medication intake and remove metal objects, such as a collar, from their body. Following these guidelines is important so the best results can be achieved. 

Your vet will examine your pet and explain the CT scan, MRI, or X-ray procedure if one is required. They'll also discuss what they will be looking for. 

If your pet's diagnostic test is scheduled ahead of time at our vet lab in Santa Barbara, your vet will give you any necessary instructions on the day of the procedure. 

Will my dog or cat be sedated when they have their diagnostic imaging test?

If your dog or cat is calm, not in too much pain, and can lie comfortably while the CT scan is taken, sedation will not be necessary.

On the other hand, sedation will be recommended if your dog or cat is squirmy, edgy, or in pain. Sedation may also be used during your pet's scan in certain cases, as they must be relaxed to get a clear image.

If biopsies are needed, your pet will require a short-acting anesthetic or heavy sedative to help them relax during the procedure and prevent potential complications. Your veterinarian will let you know if this is necessary.

For an MRI to be successful, the patient must remain still so that a general anesthetic can be administered to your dog or cat before the scan. Vets usually recommend blood tests and X-rays be completed before diagnostic tests to ensure that your pet is healthy enough to be under general anesthetic. 

Are CT scans, MRIs & X-rays safe for dogs & cats?

CT scans are very safe procedures. Like an X-ray, CT scans use ionizing radiation, but at doses that are not harmful to pets.

X-rays and CTs are typically used only occasionally and generally as diagnostic tools. In some circumstances, vets use X-ray technology to glean information about a dog's pregnancy. However, other forms of imaging, such as ultrasound, could be used in that case.

MRIs are a safe, non-invasive procedure that does not cause your pet pain or discomfort, and, unlike a CT scan, no ionizing radiation is utilized.

If you're concerned about using X-ray, MRI or CT scanner technology and your dog's or cat's health, speak to your vet. Your veterinarian will be able to explain the risks versus the benefits in your dog's or cat's particular case so that you can decide whether to have an X-ray or CT scan.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Would you like to learn more about diagnostic imaging at San Roque Pet Hospital? Contact our Santa Barbara vets today.  

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San Roque Pet Hospital welcomes cats, dogs, and their people to our clinic! Our experienced vets are passionate about the health of Santa Barbara companion animals. Get in touch today to book your pet's appointment.

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