Computed Tomography (CT)

Computed tomography (CT) is a cross sectional x-ray that allows the
visualization of internal anatomy without superimposition of structures. Computed tomography images are generated much the same way x-rays
are made, however CT images have superior contrast resolution (more gray scale) than conventional x-rays, resulting in a much more sensitive way to distinguish between solid, cystic, fatty, calcified, hemorrhagic, gaseous, or vascular structures in the body. CT allows the clinician to detect abnormalities and changes more accurately and earlier in the course of injury or disease.

Producing the CT image

The CT image is made using multiple x-ray beams coming from different directions as the x-ray tube rotates around the patient, so it is crucial that the animal doesn’t move during the study. This requires either deep sedation or general anesthesia. Each patient receives a physical examination by a VSA surgeon prior to undergoing sedation or anesthesia. Depending on the problem and age of the animal, blood work or other diagnostics may be necessary to make sure anesthesia is as safe as possible.

Current CT technology allows for continuous movement of the patient through the machine during rotation of the x-ray tube. This allows for the study to be performed rapidly, which enhances the quality of the images and minimizes the time the animal is under sedation or anesthesia. Spiral or Helical CT acquires a huge volume of data over 20-40 seconds as opposed to a single slice every 5-10 seconds (which occurs with conventional CT). A Helical CT unit is currently being used in all of VSA’s facilities.

Veterinary Indications and Applications of Computed Tomography.  

CT has greatly enhanced our ability to manage many cases. It significantly aids us in surgical diagnosis, treatment planning, and determining prognosis and outcome for a number of diseases. Here is a short list of some of the uses for CT as described recently in the veterinary literature:

• Nasal disease – May be useful in helping determine the cause of nasal discharge or swelling of the nose
• Middle ear disease – Helps direct potential surgery for ear disease
• Feline fibrosarcomas – Helps the surgeon determine how much tissue to remove
• Soft tissue sarcomas – Better surgical and treatment planning available with CT
• Pulmonary (lung) disease –Superior to conventional x-rays for detection of metastatic (cancer spread) disease
• Ectopic ureters
• Portosystemic shunts – Can often determine the presence and location of a shunt
• Adrenal masses, mediastinal masses, craniofacial masses, pelvic masses – 3D reconstruction provides information on extent and allows for more accurate surgical planning and prognosis
• Elbow dysplasia – More sensitive and specific than conventional x-rays and can be done under sedation!
• Pelvic fractures – 3D reconstruction can assist surgical planning in difficult, comminuted fractures
• Biopsy guidance – Directs nasal cavity, bone, retrobulbar (behind the eye), and intrathoracic (within the chest) biopsy instrumentation using CT
• Brain tumors or disease
• Spinal disease – Can help determine location of disc material within the vertebral (bony) canal; differentiate and locate tumors of the spine to help with surgical planning and prognosis

Because the CT images are made up of digital information, the image can be readily adjusted to enhance certain structures or regions. We can store this information digitally on computer, keep images with the patient record, and even email or create a CD of the images for clients and referring veterinarians. Computer software can manipulate the original transverse data for 2D real-time image reformation as well as very informative 3D reconstruction. We can even use “real-time” information from the CT unit to help guide biopsy sampling of organs or structures within the chest, abdomen, and pelvic canal.

Referral Information

Computed tomography will contribute to the diagnostic work-up in a variety of surgical conditions and the surgeons at VSA look forward to offering this service. We are pleased to be working with Dr. Mark Matteucci, Diplomate of the American College of Veterinary Radiologists, who provides us with expert CT and radiographic interpretation and advice.