CT Scan or CAT scan (Computed Tomography Imaging)
Computed Tomography Imaging known as a CT scan (or CAT scan) is a particular type of x-ray that uses multiple x-ray beams at different angles to build up a cross section of the body’s organs and tissues.
CT scans can show several types of tissue with great clarity such as bone, soft tissue and blood vessels and allows easy differentiation between soft tissue structures, which greatly improves on the conventional x-ray. CT scans can detect and determine the exact size and location of anatomical abnormalities such as tumours, lesions, blood clots and blood vessel defects and bone defects. The images produced are generally of cross-sectional nature, with multiple scans creating the ability to produce 3-D images of internal structures.
How does it work?
Computed Tomography Imaging works on the same basis of an x-ray. As the x-ray beams pass through the body, they are absorbed at different levels and a profile is created of x-rays beams of different strengths. These are recorded on film as an image or in the case of an x-ray, resembling a shadow. The use of a computer in CT scanning is what differs from a conventional x-ray. A CT scanner consists of a table on which the patient lies which moves in through the ring shaped scanner. A moveable ring located is on the edge of the scanner which contains the x-ray tube and its associated detectors. A CT scan involves the movable ring revolving around the patient with fine fan of x-ray beams being passed through the body from all angles into their associated detectors, with the information from each detector relating to a particular part of the body. All this information from the detectors must be compiled into a detailed image of the particular slice of the body by the computer. Every time the movable ring makes a 360 degree rotation, a slice has been acquired. These slices give such detailed images of the internal structures of the body that they have become widely used in radiology, in both the diagnosis of diseases, checking of bodily structures such as the brain, heart, liver, lungs and kidneys and also in trauma to check for injury.
The CT Scan:
Preparation for a CT scan is similar to x-rays and MRI scans. Most radiology clinics provide patients with a hospital gown, but otherwise all jewellery and items such as hats, belts, clips, and glasses must be removed as some objects have a detrimental effect on the image when scanned. In some cases contrast agents are administered to image particular tissues more effectively. Many contrasts agents do contain iodine, which can provoke an allergic reaction in some patients. If you have an allergy to iodine or any other allergies, notify the nurse, technician or radiologists before the administration of the contrast agent. If you suspect you may be pregnant or you are pregnant, you must notify your doctor before the CT scan as this procedure does involve radiation and can be dangerous to a developing foetus. A CT scan is very similar to a MRI scan.
You will be asked to lie on the table in a still position and the table will move into the tunnel. During the scan, the table will move a small distance every few seconds to reposition you for the next scan. During the scanning, the machine may make buzzing or click sounds as it moves. You will be alone in the scanning room, but the radiologist conducting the scan will be able to see you through a window into the room and communicate with you via intercom. The scan can last from 30-90 minutes, during which you will be asked to lie very still in the scanner which for some can cause anxiety or claustrophobia. If you suffer from a fear of small spaces (claustrophobia), inform your doctor and the radiologists and a sedative can be administered in appropriate conditions. After the scan, the details of the results may be shared by the radiologist or referred back to your doctor. Your day can continue as normal however it is recommended if you were given a contrast agent to drink water to flush your body of the agent.
Benefits and Risks:
Risks associated with CT scans can be associated with an allergic reaction to the contrast agent, which can lead to an allergic reaction such as a rash or nausea to more extreme and rare cases of sudden shock. An extreme reaction is very rare as the patient is constantly monitored and medical histories examined. If you do have an allergy particularly to iodine or to other substances inform your doctor, radiologist, technician or nurse. As this is a procedure that uses x-ray beams, there is a certain amount of radiation involved. The risks associated with radioactive exposure have been minimised by health professionals in a variety of ways, using the minimum amount of radiation in scanning and adjusting the radiation to body size (for example in children). It is a known fact that high levels of radiation may cause cancer, yet it is highly unlikely that level of radiation used in a CT scan will cause cancer. This risk can be outweighed by the diagnostic benefits from CT imaging in diagnosing other conditions and diseases that are already present. The benefits from CT scans enable detailed images of the internal structure of the body to be viewed and examined for any abnormalities that could be potentially fatal.