Computed tomography (CT)
Computed tomography (CT) is a modern "imaging" method that allows a detailed look into the human body.
An X-ray tube rotates around the patient and, at the same time, emits a small beam of X-rays. A detector system opposite the tube rotates around the patient as well. This is how images of organs of the body can be realised in every section from nearly one thousand directions. This adds up to hundreds of thousands of measuring values that are processed further by a computer. The results are cross-sectional images of the region of the body under examination free from overlying structures. The time of measurement of every region of the body is a few seconds only.
The examination is painless and uncomplicated for the patient.
The particular advantage compared to conventional X-ray examination consists in the improved visualisation of the soft tissues, i.e. the internal organs.
Large parts of the body can be examined in a very short time. The special imaging technique avoids the overlaying of organs as it occurs in the X-ray image (summation image), which results in clearer diagnoses. Postprocessing of measured data can produce three-dimensional images of the examined area. Moreover, density measurements can be used to find out whether it is e.g. fatty tissue, liquid or solid tissue.
Computed tomography has a very large field of application today. There is no other method to provide decisive information that quickly and precisely for examinations of the lungs, many questions regarding the abdomen and the quick examination of the head (e.g.) when searching for bleeding and injuries. Computed tomography is indispensable especially in case of accident or stroke.
Process of examination
How is the examination realised?
During the examination, the patients are lying, in most cases on the back, on a narrow bench that moves slowly into the ring-shaped opening of the system. It has a width of approx. 70 cm and the device rather is a ring than a "tube" which is why you do not need to feel constricted or have claustrophobia. During the examination, you can talk to the physician or the X-ray assistant at any time via an intercom system.
The examination itself is completely painless and takes 2 to 10 minutes depending on the problem. You should lie as relaxed and calm as possible during the examination. An automatic voice might give you exact instructions on how to breathe. Please stick to these instructions, since the internal organs may appear different depending on respiration.
Preparation for the examination
Examinations of the head (skull and brain) as well as of the intervertebral disks and parts of the skeleton do not require any special preparation. About 2 hours before the examination of the abdomen and the pelvis, 1- 2 litres of contrast agent are given to drink in most cases so that the gastrointestinal tract can be visualised. In general, this type of contrast medium does not contain iodine, but consists of a barium compound. In many cases, you have to come "fasting" to the examination, that is you should neither eat nor drink or smoke within three hours before.
Contrast agents in CT
Administration of contrast agents is required for many CT examinations. Contrast agents are used to improve the visualisation of blood vessels, tumours well supplied with blood or inflammations. They are injected into the arm vein and produce images that can be better evaluated. In case of examinations of the abdomen, it is possible that you have to drink contrast agent. In general, all contrast agents are tolerated well and are eliminated via the kidneys after a short time. Some persons show allergic reactions to iodine-containing contrast agents. Therefore, you have to complete a questionnaire before examinations with administration of contrast agent so that possible problems can be recognised before the examination already.
If you are diabetic and take tablets (metformin), you have to stop taking them two days before the examination and may start taking them again one day after the examination only. Insulin injections do not interfere with the examination.