Computed Tomography (CT scans - CAT scans)

   Many people are familiar with x-rays through their own personal experience or through their pet having them done. Computed tomography, commonly referred to as a 'CT' or 'CAT' scan, is becoming more common also. This technology is very useful when looking at parts of the body such as the brain or spine.  Computed tomography was first used in 1971 in human medicine in England. The image produced is reconstructed from many radiographic images taken of the animal. Very fine x-ray beams are sent through the body to detectors, which then send the signals to a computer, which processes the image.

The tissue images that show up on the monitor consist of white, black, and shades of gray, called the gray scale. The amount of gray shows the ability of the tissue to absorb the x-ray beam. This helps to identify tissues that are normal or abnormal, such as brain tumor versus normal brain tissue. The computer typically images the height and width of the tissue, while newer machines can give a 3-D look. Better quality of the CT image is obtained by taking thinner slices with the x-ray beams.

CT scans provide better differentiation of soft tissue than conventional x-rays since, the gray scale can be controlled by the technician. A contrast media (dye) can also be injected into the patient's bloodstream to further increase the differentiation of tissue. The CT scan also does not superimpose the bone over the soft tissue, as it is only looking at a slice of the body at a time.

Animals who are candidates for a CT scan include those with neurological disorders, such as seizures, behavior changes, or problems walking. The animal is anesthetized with a general anesthesia during the procedure, since she must remain completely still. The table on which the animal is laying is slowly advanced into the part of the machine that performs the scan (called the gantry) as the x-ray tube rotates 360 degrees around them.