Computed tomography (CT)

Index

Computed tomography ( CT ) is an imaging method that can be used to create cross-sectional images of all organs in the human body, but also of the skeletal system, in various slice thicknesses.

What is computed tomography (CT)?

Computed tomography differs significantly from magnetic resonance imaging – the latter is also known as magnetic resonance imaging. In contrast to the magnetic resonance tomograph, the computer tomograph does not consist of a closed but an open tube. He also works with X-rays , the magnetic resonance tomograph builds up magnetic fields.

The first CT device was put into operation in 1972. Even then, it enabled a very good representation of the soft tissues of the human body, which is why computed tomography was immediately used by many radiologists.

The computer tomograph itself consists of three elements: the X-ray tube, the detector system and a computer that graphically displays the data supplied. To do this, the tomograph sends a very narrow X-ray beam to the intended region.

The X-rays are reduced by the body to varying degrees, which the detectors detect and convert into signals. The cross-sectional images of the computed tomography are then created from these signals of different intensities.

application and function

Computed tomography can be used to detect diseases of all organs, but also of the skeletal system. It is very often used, for example, to examine the thorax (lungs). Here she can show even the smallest tumorous changes.

The same is of course also possible with the examinations of all other organs as well as the skeletal system. Changes in the intervertebral discs, such as herniated discs , can also be precisely diagnosed with their help. With the help of computed tomography, it is also possible to inject medicinal substances into the spinal area to alleviate symptoms. This requires several appointments.

Of course, the CT can also be used to diagnose broken bones, bleeding, swelling and inflammation. Since the computer tomograph has a larger tube than the magnetic resonance tomograph, obese (overweight) people can also be examined without any problems. Those who suffer from claustrophobia (fear of narrow spaces) should also use computed tomography instead of magnetic resonance imaging.

What does the patient have to consider in advance?

In order to be able to show some organs, but also the bloodstream, better, the patient is given a contrast agent before the start of or during the computed tomography. Therefore, the radiologist absolutely needs two laboratory values - the TSH and the creatinine value. The TSH value provides information about whether the patient suffers from a thyroid disorder.

The creatinine value is required because the contrast medium is excreted via the kidneys. If the creatinine value is not in the normal range, damage to the kidneys must be assumed. If there is a thyroid and/or kidney disease, another non-iodine-containing contrast medium is used. If time permits, each patient must also fill out a questionnaire. Here, for example, medication taken, but also various previous illnesses must be specified.

In contrast to many other examinations, your CT can be carried out relatively quickly and without much preparation. If possible, the examination should be done on an empty stomach. If it takes place in the afternoon, patients can still eat something early in the morning.

At best, you should inquire about this when making the appointment. In any case, patients should not wear any metallic objects such as earrings, piercings or rings. These can lead to so-called image artifacts, which only imprecisely depict the examined organs. The patient does not necessarily have to undress for the examination itself, as the X-rays penetrate the clothing. Only a possibly existing belt and the shoes should be removed before the computed tomography, as well as the glasses.

process and implementation

The computed tomography itself works as follows for the patient: At the agreed time, he appears with the referral and the laboratory values noted on it. He may have to drink a contrast medium solution beforehand – either at home or in the practice. The patient is then led to a changing room where they must leave all personal and metal belongings. He then lies down on a mobile table that moves into the tube at the beginning of the examination.

A medical-technical assistant (MTA) may place an intravenous access through which contrast medium can also be applied. It also has a knob that sends a signal to the computer-aided workstation when it is pressed. He can use this to draw attention to indisposition, for example, but also to other problems. For certain recordings, the employees will also give a breathing command, which should be followed at all costs.

After the completely painless examination, there is usually a discussion with the examining radiologist, who already informs the patient of the first results. In an emergency, he will also be given a report of the findings as well as the images from the CT – for example on CD-ROM, but perhaps also as a printout.

Risks, dangers and side effects

As already mentioned, computed tomography uses X-rays that are many times more intense than conventional X-ray examinations. However, the dose of radiation depends on the area examined.

For example, a CT of the head only uses a radiation dose of 1.5 to 2.3 mSv (millisievert), while the radiation dose for a computed tomography of the thorax, abdomen or pelvis is 9.9 mSv.For comparison: The annual natural radiation absorption is 2.1 mSv, a chest x-ray requires 0.02 to 0.1 mSv. For these reasons, for example, an X-ray examination of the thorax should always be preferred to a computer tomography of this region – if possible.

The costs for a conventional X-ray examination are also significantly lower than for a computed tomography. These are only surpassed by the cost of an MRI scan.