>> What is a CT scan and what does it do?
The scan produces a series of images and can detect many conditions that do not show up on conventional x-rays. Your doctor has ordered this examination to help make an accurate diagnosis of your condition. The results help determine the best course of treatment for you.
During the scan, a thin beam of x-rays is focused on a specific part of your body, such as the head, chest, liver, spleen, pancreas, adrenal glands, kidneys, or spine. The x-ray tube moves rapidly around this site, enabling multiple images to be made from different angles to create cross-sectional picture. The x-ray beam is picked up by an electronic detector which records the information and feeds it into a computer.
The computer then analyzes the information and constructs an image on a monitor screen including a volume display of your organ. During some CT scans, a contrast medium (commonly called "dye") is used to outline blood vessels or highlight organs of the body (eg, liver, kidneys) so that they can be seen more easily.
>> Who performs the test?
Although your personal physician requests the CT scan, a radiologist performs the actual examination. A radiologist is a medical doctor who specializes in the use of imaging for diagnosis of medical conditions. The radiologist is assisted by a radiologic technologist, a person who has extensive training in the use of x-ray equipment. Together, these highly skilled professionals will make sure that your CT scan pictures are of the best quality possible and that you are as comfortable as possible throughout the procedure.
>> How long does it take?
Coming in and out of the examination room, a CT scan of the body can take around 7 minutes, while a scan of the head alone can take about 3-5 minutes. However, you may need to allow extra time for each procedure in case there are delays or a need to repeat some scans. Your doctor or the office nurse will advise you how to plan your schedule for the day of the exam.
>> What you can do to help make it a success
A CT scan is usually painless. The machine does not touch you and you do not feel the x-rays. Occasionally, some patients are administered a contrast medium. This may be given orally or by injection e.g. an intravenous injection. In some patients, the actual injection can be associated with a sensation of warmth, heat or flushing. These feelings are transient and will typically resolve spontaneously.
You can help assure a successful, comfortable procedure by carefully following the instructions of your physician, the radiologist, and the radiologic technologist. Be sure to answer carefully any questions they may ask about your general health. For example, tell them if you are pregnant, diabetic, and/or allergic to any foods or drugs. Let them know if you have had any contrast media in the past and if you had any side effects. Give them a complete list of any medications you may be taking now, including nonprescription medications. Also indicate if you have had or are presently being treated for an infection in any part of your body.
>> What to do before your exam?
This guide provides a step-by-step description of what to expect before, during, and after your CT scan. But please remember that it is only a guide. Some steps may vary depending on your condition, the personal preferences of your physician, and the standard procedures of the hospital or office where the test is performed.
As with other important diagnostic procedures, you may be asked to sign an informed consent to undergo a CT scan. That is your opportunity to ask any questions following a description of the risks, benefits, and alternatives of the procedure. The contents of this guide are for your information only and are not to be interpreted as taking the place of informed consent. Do not hesitate to discuss your upcoming CT exam with your physician or the radiologist.
Following are a few steps that your doctor may ask you to take before you go to the hospital or radiologist's office for your exam. These same general steps may be recommended if you are a hospitalized patient.
If a contrast medium is to be used during your CT scan, your doctor will probably ask you not to eat anything for three or four hours or more before the exam. In addition, you may be asked not to drink anything for one hour before the exam.
>> What happens during your exam?
You will be asked to lie on a table that is connected to the CT scanner. Then the part of your body that is to be scanned will be positioned in the middle of the large, doughnut-shaped scanner ring. This ring holds the x-ray tube and the electronic detector that sends information to the computer.
If a contrast medium is to be used during your exam, the technologist will probably take some preliminary scans before the radiologist injects the material.
If a contrast medium is used, the radiologist or technologist will usually inject it into a vein, probably in your arm. Some or all of the solution may be injected by a syringe or by an automatic injector. Some or all of it may run slowly into your vein from an intravenous (IV) bottle that hangs on a pole next to the table. A tourniquet may be used to make the vein stand out for easier injection. A tourniquet is simply a band that is wrapped tightly around your arm, similar to, but smaller than, the cuff that is wrapped around your arm when you have your blood pressure taken.
You will remain alone in the room after the procedure begins, but the radiologist and the radiologic technologist will watch you closely through an observation window and you can talk to them through a two-way intercom.
The table may move a short distance every few seconds to position you for each new scan, or the table may move continuously very slowly. You will hear clicking or buzzing sounds as the mechanism in the scanner moves around your body, making images from many different angles. It is important that you lie very still during the procedure so that the scanner can get the best possible pictures and hold your breath upon request by the radiologist or technician.
The entire procedure including positioning on the table and effective Xrays procedure may take about 7 minutes for a body scan and 3 to 5 minutes for a head scan.
>> What to do after your exam?
After the exam is over, the radiologist will look at all the images to make sure they contain all the needed information. You will be asked to wait while this is done because sometimes it is necessary to do repeat scans or take additional scans.
After the radiologist has a complete set of scans, you may change back into your clothes and go home. If you are a hospitalized patient, you may go back to your room.
Unless you have other tests scheduled, you may eat normal meals after the exam and your doctor will suggest that you drink plenty of fluids. Fluids will help eliminate the contrast medium from your body by natural routes.
The radiologist will study all the scans, prepare a report, and forward it to your personal physician and sometimes will gives it to you according to the rules applied by the radiology department. This may take one or two days. Then your physician will discuss the results with you and tell you what they mean to your health.