CT Imaging- Questions and Answers for the Pet Owner
Q. What is CT?
A. CT uses a thin rotating x-ray beam and computer technology to produce high detailed pictures of many parts of the body. It is especially good at imaging the bone and soft tissues of the body. Because CT can show problems that cannot be seen with other diagnostic imaging techniques, it has rapidly become a powerful diagnostic imaging modality in human medicine.
Q. How does CT work?
A. CT (or CAT) stands for Computed Axial Tomography. This technique of imaging uses an X-ray tube that rotates in a large circle around the patient. A thin x-ray beam passes through the body and is detected by a large number of computer detectors located around the same circle. The computer assimilates all the acquired information about the density of tissue the x-ray beam travels through, then produces a cross sectional image of any plane through the body. In a sense, it’s like dividing the body part into thin slices, like a loaf of bread, which can be taken apart and analyzed individually. The anatomic detail and contrast is far greater than can be achieved with conventional radiographic studies.
Q. Are there any risks with CT studies?
A. CT in itself is a very safe procedure. Like an x-ray study, CT utilizes ionizing radiation, but at doses that are not harmful to people or pets. Because patients need to be absolutely still during the CT study, however, general anesthesia is required for animals. To minimize risks associated with anesthesia, the renal, hepatic, and cardiac status should be evaluated prior to CT studies.
Q. What work-up is required before the CT?
A. Appropriate lab tests are needed to evaluate any underlying disease processes, and to ensure that anesthesia can be safely performed.
Q. How long does a CT scan take to perform?
A. CT scans allow us to acquire numerous cross sectional images (providing 30 to 60 different pictures) and take from 10-20 minutes to complete. Scans are performed with the animal under general anesthesia.
Q. Why does CT scanning require anesthesia?
A. Anesthesia is required in order to insure that the animal is perfectly still during the examination so that high quality images can be obtained for proper diagnosis.
Q. Are there side effects to the anesthesia?
A. Most animals have little or no side effects from the anesthetic. Some animals may be drowsy or a little clumsy in walking and may have some vomiting after the anesthesia. General anesthesia is a serious matter, especially in a critically sick or unstable animal, and there can occasionally be severe reactions to the procedure that can be life threatening. There can also be allergic or other adverse reaction to the anesthetic in some animals, however these are very rare.
Q. CT scans seem expensive. Why is that?
A. CT scanners are expensive to purchase, install, and maintain and they often require expensive upgrades. Our CT scan prices not only include performing the scan itself, but also include the services of our anesthesia and all drugs and anesthetic agents. In addition our prices include the services of a radiologist consultant for interpretation. When one considers all of these factors plus the enormous amount of information gained about the animal’s condition, the cost is generally well justified. A CT scan requiring general anesthesia in a human would cost 4 or 5 times as much.
Q. What conditions are CT scans useful in diagnosing?
A. CT is very useful in diagnosing disorders of the head, spine, joints, soft tissues, and bone. Common conditions diagnosed are nasal and sinus problems, middle and inner ear disorders, tumor detection and localization for surgical planning, musculoskeletal and skull trauma, spinal disease, thoracic metastasis evaluation, and evaluation of degenerative problems in some joints.
Q. What if contrast enhancement is required?
A. In order to visualize some abnormal structures such as tumors, it is often necessary to perform a CT scan after the intravenous injection of an iodine containing contrast agent. This substance is dense to X-ray and allows us to see normal and abnormal vascular structures that might otherwise go undetected. The contrast is relatively safe, although serious allergic reactions can rarely occur.