CT Scan (Computed Tomography) and CAT Scan (Computed Axial Tomography)
Computed Tomography (CT) imaging is also known as CAT scanning (Computed Axial Tomography). The machine resembles a large square with a ring in the middle. CT has the unique ability to image soft tissues (e.g. blood vessels) and renders more detail of bony structures than MRI (Magnetic Resonance Imaging). CT images reveal the relationships between soft tissue and bone.
In orthopaedic medicine, CT is an important diagnostic tool. Following trauma, it often is the imaging method of choice because the exams are fast and simple. The images help diagnose intervertebral disc herniation, fractures, and other spinal disorders. The images appear as cross-sectional slices of the patient's anatomy.
Prior to the exam, the patient is instructed to remove any metal objects (e.g. belt, jewelry, hairpins) and change into a gown. Some CT examinations require a contrast agent to be injected (or intravenously) into the patient's bloodstream. A contrast agent serves to enhance a particular body part (e.g. intervertebral discs).
After the patient is comfortably positioned on the table, the technician leaves the room and enters the adjacent control room. Throughout the exam the technician observes the patient through large windows and will converse with the patient by means of an intercom.
During the test, the patient must lie still and may be asked to hold their breath for a several seconds from time to time. The patient may hear the scanner rotating during the study - this noise may be soft or more audible. Depending on the type of study, the CT scanner or table will move slightly as low intensity x-ray beams are rotated at many angles around the patient. A computer collects the data from the scanner, calculates the density of a given cross-sectional slice, and produces the image onto film for study by a radiologist.
Important Considerations
If the patient's CT scan is to include a contrast agent, any known allergies should be discussed with the referring physician prior to the test. The test may be postponed if the patient is pregnant or nursing.