Risks of computer tomography

Since the basis of the computed tomography examination is X-rays, the examination results in radiation exposure. Depending on the examination, the radiation exposure is indicated between 3 mSv and 10 mSv (1 mSv = 1/1000 Sievert). A classic chest X-ray is approx.

0.3 m Sv. For comparison: the natural radiation exposure at sea level in Germany is approx. 2.5 mSv per year.

Contrary to general opinion, the radiation exposure is therefore rather low. A further risk is the suffering of a panic attack during the examination due to the oppressive conditions. If claustrophobia (claustrophobia) is known, sedatives can be given before the examination if necessary. More and more open computer tomographies are coming onto the market, in which patients only have to be driven through the CT ring.

Contraindication

Computer tomography is, as mentioned, an X-ray examination. For this reason, patients should generally not be examined by computer tomography during pregnancy. Since contrast medium containing iodine is used for CT examinations, it must be determined in advance of the examination whether the patient has any known allergic reactions to the contrast medium or to iodine.

In addition, the function of the thyroid (hyperthyroidism) and the kidney (limited excretory function?) should be clarified by laboratory tests. The patient is placed on an examination table for computer tomography.

Depending on the area to be examined, either the entire patient or only the region to be examined is then passed through the tomograph. Just as with photography, the quality of the images produced by computed tomography improves the more quiet the patient lies during the examination. In most cases, the radiologist where you have the examination performed will provide you with further information in an information brochure. In general, the patient does not have to come to the CT scan on an empty stomach.

Computed tomography head

A computer tomography of the head is often abbreviated as cCT (where c stands for cranial) in everyday clinical practice. During the examination, the patient, who is lying on a mobile couch, is driven through the device, which produces numerous sectional images of the head within a short time. Depending on the issue at hand, the patient is injected with contrast medium via the vein in order to make certain processes more easily visible or distinguishable.

Computed tomography is used for numerous problems and is particularly widespread in the field of neurology. Computed tomography of the head usually provides valuable information when it comes to clarifying acute processes in the brain and skull. One of the most important indications for a timely cCT is the suspicion of intracranial hemorrhage.

This can usually be clearly delineated in the CT, as it appears brighter (hyperdens) than the surrounding brain tissue. Sudden severe to very severe headaches can often be an indication of such a cerebral haemorrhage. In this respect, the preparation of a cCT is diagnostically valuable.

In mostly rather younger people who describe a sudden “destruction headache”, this may be an indication of a subarachnoid haemorrhage (SAH), which is often caused by the rupture of a vascular malformation in the brain, an aneurysm. If older people complain of headaches, this should make them audible, especially if they have fallen in the immediate past and if they are taking blood thinners. Bleeding can also be the cause, usually in the form of an epidural or subdural haematoma.

Patients who present with rather subacute headaches of medium intensity and who also require clarification by means of imaging of the head are usually more likely to have an MRI of the head. Another very common indication for performing a head CT is the exclusion of fractures after falls or accidents. Here, CT is the gold standard, as it has the best resolution in the area of bone structures.

A stroke can also generally be clarified using a cCT. If it is the rather rare form of haemorrhagic infarction, i.e. a stroke caused by bleeding, it can usually be clearly defined with CT. If it is a stroke caused by reduced blood flow (ischemic infarction), magnetic resonance imaging is usually more suitable in the acute stage, and it also has a significantly lower radiation exposure.

In the course of the disease, an ischemic stroke also shows up on CT. However, if a stroke is suspected, a cCT is usually performed first to gain initial insights into the development of the stroke. Another possible indication for a CT scan of the head is recurrent dizziness, which can be an indication of circulatory problems in the brain.

Often, however, MRI can be given preference here as well, since it can depict structures essential for the development of dizziness, sometimes in more detail than CT. Depending on the type of cancer, cCT is also frequently performed on patients with cancer, especially if the patients describe symptoms such as dizziness, headaches or neurological deficits such as speech or vision disorders, paralysis or sensitivity disorders. In this case, there is a risk that the tumour has metastasised to the brain or that a brain tumour has developed.

This suspicion can first be clarified with a cCT, but in most cases MRI provides the better resolution for this question. MRI is generally preferred to CT for the clarification of inflammatory processes, for example in the context of multiple sclerosis, in the suspicion of tumours or metastases in the brain and for the clarification of processes in the area of the cranial nerves, the cerebellum and the brain stem. It is therefore clear that it is not easy to give a very clear indication for cCT and against MRI or vice versa. In short, however, it can be said that cCT after trauma, in cases of suspected cerebral haemorrhage, in post-stroke conditions and in cases of unconsciousness have a very high priority.