Computed tomography, or CT for short, is another imaging technique, along with X-rays and magnetic resonance imaging and ultrasound. It is created using X-rays, which are internationally known as X-rays (X-Ray). Because computed tomography produces individual cross-sectional images, they must be projected on top of each other by computer to produce results.
History and function
In the X-ray process, X-rays pass through the body and are imaged on an X-ray image. In computed tomography, the body is transilluminated from many directions and displayed in three dimensions on a computer. Click to enlarge. The Austrian mathematician Johann Radon, the physicist Allan M. Cormack and the electrical engineer Godfrey Hounsfield may be called the inventors of computed tomography. The first computer tomograph was put into operation in 1972 in London at the Atkinson Morley Hospital. In 2009 alone, approximately 4.88 million patients in Germany were examined using computed tomography. Computer tomography is not only used in the medical field, but also in archaeology for the examination of ancient objects, but also for the examination of mummies. It was also used, for example, to determine the age of the “Ötzi” found in the Alps. Computed tomography is also used in industry.
Application
In the field of medicine, computed tomography is used by means of the spiral technique. Here, the patient is slowly passed through the device while the device rotates. Computed tomography is used, for example, in the examination of the head. Here, by means of contrast medium, the individual arteries, but also brain areas, can be efficiently displayed. The first series of examinations is usually performed natively – i.e. without contrast medium – and the second is then performed after the contrast medium has been administered. This makes any changes in the tissue even more noticeable. Computed tomography is also used to examine the thorax, abdomen, upper abdomen, the entire spine, and in some cases also the limbs. This is especially the case in obese patients. While the patient lies in the computer tomograph, the sectional images are processed by an external computer with the appropriate software. The staff of the practice or hospital also sit in a separate control room, but maintain contact with the patient via a microphone. If a patient experiences problems, such as claustrophobia, during the CT scan, he or she can provide feedback at any time and is then either administered a drug to sedate, or immobilize, or the CT scan is discontinued after consultation with the physician.
Side effects and hazards
Computed tomography has some advantages over other imaging modalities, but it also has a few disadvantages. For example, it is much more radiation-intensive than an X-ray exam. For example, computed tomography uses up to 50 times the radiation dose of conventional mammography, and compared with chest X-ray, the radiation dose of computed tomography is even up to 575 times higher. Therefore, one should carefully consider whether to have a computed tomography performed. Those who suffer from claustrophobia should prefer computed tomography over magnetic resonance imaging. Obese (i.e., overweight) patients should also be examined using computed tomography because the MR scanner “tube” is much narrower than the CT scanner. One advantage of computed tomography is that the cross-sectional images are of much better quality than individual radiographs. Compared to magnetic resonance imaging – which uses magnetic fields rather than X-rays – it is much less expensive. Since new computed tomography scanners have a much lower radiation exposure than old scanners, it is advisable to visit a doctor’s office or hospital where computed tomography is part of the standard examinations. Here you can assume that the latest equipment is used. Nevertheless, a computer tomography should not be performed too often, since the radiation dose – as an example, coronary computer tomography – can be up to about 14 millisieverts per examination.An employee of a German nuclear power plant may be exposed to a radiation dose of 20 millisieverts per year. This comparison should be kept in mind before performing a computed tomography. However, if computed tomography is deemed medically necessary after consultation with the physician, it should not be dispensed with. The radiation dose also dissipates relatively quickly. Nevertheless, the risk of cancer is higher after a performed computed tomography.
