How does a CT Scan work

CT is a computerised continuous x-ray imaging procedure that generates cross-sectional images or ‘slices’ of the body. Powerful computers use complex software to digitally ‘stack’ these images together to form a 3D image of the patient that we can accurately recognise and interpret. Unlike plain x-ray, a CT scan can differentiate between different types of soft tissue and thus can be used in the investigation of a wide array of conditions. With the administration of an intravenous contrast agent a ‘Contrast CT’ can detect subtle regions of pathology for example in the assessment of metastatic cancers.

What is a CT Scan used for a Eden Veterinary Referrals?

CT scanning is most often used for examining noses, lungs, the contents of the abdomen, and bones. CT has revolutionised the way the veterinary profession looks at problems within complicated joints such as the elbow, for example.

Download CT Referral Form

Here are some examples of how useful CT Scans can be…

Joints

CT scanning is particularly useful at looking at complex joints (those that are difficult to fully assess with normal X-rays or are composed of more than two bones). CT is used extensively to evaluate the elbow joint, as it is notoriously difficult to assess by radiography.end of antibiotic treatment will also be required prior to surgery.

CT of the left elbow joint in a 7-month-old Labrador. The medial coronoid process has a heterogenous attenuation, with marked sclerosis. There is a well-defined, triangular bone fragment (4,5 mm x 2,5 mm), located in-situ, at the level of the apex (orange arrows). The radial notch of the ulna is slightly irregular, with multiple hypoattenuating lesions. There is a small concave subchondral bone defect at the medial aspect of the humeral condyle (pink arrow), surrounded by a severe diffuse area of sclerosis (blue arrows).

Chest

CT is extremely useful at looking at the chest, particularly for those structures filled with air (the lungs and the windpipe or trachea). It has revolutionised the way we detect diseases that may have been very difficult to assess on normal X-rays. CT is particularly useful at assessing the acute trauma cases we see, allowing us to diagnose the extent of their injuries.

CT of thorax in a 13-year-old Cocker Spaniel. There is a moderate volume pneumothorax on the right-hand side of the thorax. There is a large, single, thin walled, air attenuating structure with a thin band running across the centre which arises from the cranial aspect of the right cranial lung lobe diagnosed as a pulmonary bulla

Abdomen

CT scanning is very useful for looking at soft tissues within the abdomen because it is quick (much faster than MRI) and can spot changes that can be seen after contrast (dye) is injected. Using contrast agent is very useful for looking at abnormal blood vessels in the abdomen, such as those seen in a condition called a portosystemic (liver) shunt (see our Portosystemic Shunts Information Sheet), as well as for many other diseases such as neoplasia (cancer).

CT of a single extra-hepatic portocaval shunting vessel (green arrowheads). Reduced portal vein diameter (red arrowheads) cranial to shunt with reduced visible of the intra-hepatic portal vessels suggestive of concurrent hypoplasia.
CT scan of the abdomen in an 11-year-old cross breed dog. A large (8.5x9cm) hepatic mass is observed within the right cranial abdomen, originating from the right hepatic division (blue arrows) and displacing the descending duodenum/ right lobe of the pancreas and ascending colon to the left. It is originating most likely from the caudate process of the caudate lobe.

Nose

CT scanning has largely replaced normal plain radiographs for looking at diseases of the nose. This is because normal X-rays are not very sensitive at looking at nasal disease (that means they often miss the disease that is present) and even worse, can often suggest disease is present when it is not. Nasal cancer is often assessed by CT, in addition to a host of other diseases such as infectious and inflammatory causes of rhinitis, cysts, polyps and foreign bodies to name a few.

Caption below image: This is a CT image of the nasal cavity of an 11-year-old DSH cat. There is non-contrast enhancing, soft tissue attenuating material filling most of the left nasal cavity and left frontal and sphenoid sinuses with no apparent significant destruction of the nasal turbinates. Giving us a diagnosis of Left-sided non-specific rhinosinusitis.