While CT imaging was initially reserved for veterinary universities and referral hospitals, the technology is making its way into some general practices.
Like any technology, it becomes more compact, affordable, and practical to own over time, so a CT scanner might be a reasonable option for practices in some locations.
Here is an overview of CT in veterinary medicine, which will be followed by a deeper dive into the technology and its uses in the next few articles.
What Is CT?
CT stands for computed tomography, and it’s a specialty type of imaging modality. It uses x-ray technology, but instead of a single 2D image, the machine circles around the body to produce “slices” or cross-sectional images of the area being evaluated. Added up, these cross-sections allow the veterinarian to get more of a 3D look inside the body.
Depending on the technology being used, this could be performed by scanning a thin slice of the patient, then advancing them a little further into the machine (just a few millimeters at a time) and obtaining another slice, then repeating until the entire area under study has been imaged in this manner.
New technology features “multi-slice” imaging in which many cross-sectional images can be obtained simultaneously. As you might expect, newer technology can perform the task much faster.
Advantages of CT Scans
Some of the “pros” of CT technology, compared to other imaging modalities, include…
Overcoming superimposition. The cross-sectional nature of the images allows a veterinarian to see much more than they could with just a few traditional x-ray views. It reduces or eliminates the problem of superimposition. This is especially valuable for structures such as the skull, which is notoriously difficult to radiograph due to superimposition of the many structures inside the head, nose, etc. Another example might be a soft tissue mass in the abdomen that overlaps with structures such as the liver. CT imaging helps a vet see deep or superimposed structures more clearly.
Better tissue differentiation. Compared to conventional radiographs, CT allows better differentiation of tissues and more precise detection of x-ray attenuation, especially for neighboring soft tissue structures. Examples might include visualizing individual muscles, differentiating vasculature from surrounding tissues, or being able to see a mass in the brain or within an abdominal organ such as the liver or spleen. For these reasons, CT is often a great choice for evaluating musculoskeletal lesions and looking for/describing the extent of lung metastasis.
Contrast studies. These may be performed when more information or differentiation is needed. Although CT generally provides excellent detail, contrast studies may help further characterize a lesion.
Surgical planning. CT can help surgeons plan for a complicated mass removal—such as with nasal tumors, intrathoracic neoplasias, and more—by delineating and characterizing the full extent of the abnormal growth.
Disadvantages of Using CT
While CT is a great modality that is superior to conventional radiographs in many ways, every technology has its pros and cons. Here are some challenges to consider for using CT…
Anesthesia. Dogs and cats must usually be anesthetized for their CT scan. This allows proper positioning and prevents motion artefact. Even something as simple as normal respiration might create motion artefact. Ventilation may be controlled during the shot while the patient is anesthetized, to prevent motion as well as lung atelectasis that could be mistaken for a lesion.
Costs. Although more affordable than it once was, there’s no doubt that CT machines can be a significant financial investment—in terms of both the initial purchase and the upkeep. Given the cost of the technology, as well as the added costs of general anesthesia, some clients might be deterred by the price tag of a CT study. It may still be more affordable than MRI, though, in cases in which a CT study can be used in place of MRI (there are many).
Size constraints. This applies to both the patient and the hospital. Some CT models, especially smaller machines like cone beam CT, only fit patients of a certain size. Although they might still be used for the head or extremities of larger patients, this would eliminate some potential studies altogether on large dogs or other big patients. It’s also important to consider the footprint of the machine itself and where it will fit in the hospital.
Learning curve. CT images look a bit different than traditional x-ray images. Not to mention, most vets aren’t familiar with the evaluation of cross-sectional images. As with any new skill, it can take time and training to feel up to speed and confidently interpret CT studies. Plus, the staff must learn how to use the machine. Fortunately, there are many resources (texts, courses/training, etc.) to help. Also, teleradiology consultations are available for added support.
With all the potential uses of CT, it’s no surprise that it seems to be gaining in popularity and is available at some general veterinary practices. It will be exciting to see how the technology continues to evolve over time to advance veterinary medical knowledge and patient care.
Written by: Dr. Tammy Powell, DVM
