How
should I prepare for the procedure?
What
does the equipment look like?
How
is the procedure performed?
What
will I experience during the procedure?
What are the benefits
vs. risks?
Are there any side effects
?
How
long does it take ?
How should I prepare for the procedure?
You should wear comfortable, loose-fitting clothing for your CT exam. Metal objects can affect the image, so avoid clothing with zippers and snaps. You may will also be asked to remove hairpins, jewelry, eyeglasses, hearing aids, and any removable dental work, depending on the part of the body that is being scanned. You may be asked not to eat or drink anything for one or more hours before the exam. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
What does the equipment look like?
The CT scanner is a large, square machine with a hole in the center, something like a donut. The patient lies still on a table that can move up or down, and slide into and out from the center of the hole. Within the machine, an x-ray tube on a rotating gantry moves around the patient's body to produce the images, making clicking and whirring noises as the arm moves. Though the technologist will be able to see and speak to you, you will be alone in the room during the exam.
How is the procedure performed?
The technologist begins by positioning the patient on the CT table. The patient's body may be supported by pillows to help hold it still and in the proper position during the scan. As the study proceeds, the table will move slowly into the CT scanner "donut". Depending on the area of the body being examined, the increments of movement may be so small that they are almost undetectable, or large enough that the patient feels the sensation of motion.
A CT examination often requires the use of different contrast agents to enhance the visibility of certain tissues or blood vessels. The contrast agent may be injected directly into the blood stream, swallowed, or administered by enema, depending on the type of examination. Before administering the contrast agent, the radiologist or technologist will ask whether the patient has any allergies, especially to medications, iodine, or shellfish, and whether the patient has a history of diabetes, asthma, a heart condition, kidney problems, or thyroid conditions. These conditions may indicate a higher risk of reaction to the contrast agent or potential problems eliminating the agent from the patient's system after the exam.
A CT examination usually takes from fifteen minutes to half an hour. When the exam is over, the patient may be asked to wait until the images are examined to determine if more images are needed.
What will I experience during the procedure?
CT scanning causes no pain, and with spiral CT, the need to lie still for any length of time is reduced. For different parts of the body, the patient preparation will be different. You may be asked to swallow a liquid contrast agent that allows the radiologist to better see the stomach, small bowel, and colon. Some patients find the taste mildly unpleasant, but most can easily tolerate it. Your exam may require the administration of the agent by enema if the colon is the focus of the study. You will experience a sense of abdominal fullness and may feel an increasing need to expel the liquid. Be patient; the mild discomfort will not last long.
Commonly, a contrast agent is injected into a vein to better define the blood vessels and kidneys, and to accentuate the appearance between normal and abnormal tissue in organs like the liver and spleen. Some people report feeling a flush of heat and sometimes a metallic taste in the back of the mouth. These sensations usually disappear within a minute or two. Some people experience a mild itching sensation. If it persists or is accompanied by hives (small bumps on the skin), the itch can be treated easily with medication. In very rare cases, a patient may become short of breath or experience swelling in the throat or other parts of the body. These can be indications of a more serious reaction to the contrast agent that should be treated promptly, so tell the technologist immediately if you experience these symptoms. Fortunately, with the safety of the newest contrast agents, these adverse effects are very rare.
What are the benefits vs. risks?
Benefits
Unlike other imaging methods, CT scanning offers detailed views of many types of tissue, including the lung, bones, soft tissues, and blood vessels. CT of the head is now widely available and is performed in a relatively short time and at a reasonable cost - especially when compared to MR imaging.
CT examinations are fast and simple. Especially in trauma cases, they can reveal internal injuries and bleeding quickly enough to help save lives.
It is the only method that provides detailed images of bone, soft tissue, and blood vessels.
CT is becoming the method of choice for rapidly screening trauma victims to detect internal bleeding or other life- threatening conditions.
CT scanning is painless, noninvasive, and accurate.
Diagnosis made with the assistance of CT can eliminate the need for invasive exploratory surgery and surgical biopsy.
CT does involve exposure to radiation in the form of x-rays, but the benefit of an accurate diagnosis far outweighs the risk. The typical radiation dose from a CT exam is equivalent to the amount of natural background radiation received over a year's time. Among all radiological procedures, radiation exposure from CT of the body is intermediate.
Special care is taken during x-ray examinations to ensure maximum safety for the patient by shielding the abdomen and pelvis with a lead apron, with the exception of those examinations in which the abdomen and pelvis is being imaged. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
Nursing mothers should wait for 24 hours after contrast injection before resuming breast feeding.
The risk of serious allergic reaction to iodine-containing contrast medium is rare, and radiology departments are well equipped to deal with them
This study is contraindicated in pregnancy (due to harmful effects of radiation on foetus). There is no other condition in which a CT scan study is contra indicated. In case an intra venous injection is given, it should be well tolerated by you. In the event of an allergy reaction, nausea, itching, a skin rash or similar mild reaction may occur. In rare cases, there could be hypersensitivity reactions. Patients with a history of allergy to drugs, foods, history of allergy to contrast media, bronchial asthma, gout, and thyroid disorders are at a slightly greater risk to developing a contrast reaction. Two types of contrast are available - non-ionic and ionic type contrast; generally the risk is minimum with non-ionic contrast media.
A plain and contrast study of the head would take around 10-15 minutes, while body scanning would take longer depending upon the part scanned approx. 30 min. Nowadays, spiral CT scanners are available which reduce the time of scanning and also provide greater accuracy in certain conditions.
