Procedure: Ct Bodypart: Musculo Patient Group: Female Male Child Summary Synonyms: CT of the skull, CCT, cranial CT, CT of the neurocranium, skull CT A CT examination of the skull is the most important primary examination procedure for the representation of changes in the skull bones. After magnetic resonance imaging (MRI), it is the most important diagnostic imaging method for questions which concern the brain. Technique What it is The computed tomograph (CT) is a modern X-ray apparatus which rotates and completely scans the body with X-rays to produce representative images as layers or as three-dimensional models. How it works In the CT, an X-ray apparatus and a digital X-ray detector are mounted opposite each other in a ring. This ring is cased in a gantry (casing) that rotates around the body at high speed. Lying on a mobile examination table, the patient is pulled through this ring and the CT makes numerous X-ray images. These are then converted into an image of the body by a computer. This image typically shows the density of the different organs and tissues. The radiologist then screens the complete examined area, layer by layer, and can identify pathological changes and abnormalities with a high degree of certainty. For certain diagnostic tasks, e.g. a blocked blood vessel that supplies the brain, a contrast agent is injected into a vein, typically in the forearm, immediately prior to the procedure. Thus, the vessels themselves are made visible. Purpose Target Patient Group
. The exclusion of an injury of the brain, blood vessels and bones after a fall or accident: An accident may cause injuries to both the brain and the surrounding bones. Such injuries are potentially life-threatening, so early recognition is important to prevent consequential damage. The computed tomography is frequently used as the first radiological examination thanks to its widespread availability. 2. The exclusion of a cerebral haemorrhage: Bleeding in and around the brain tissue can be the result of accidents and can also be caused by spontaneous malformations or wear. Early detection is often decisive here. 3. Diagnosis of a stroke Strokes arise from an insufficient blood supply, thus a restricted supply of oxygen to the brain. In the early phases of a stroke, the detection rate of computed tomography is inferior to magnetic resonance imaging. However, it can provide important indications and exclude many other causes of a disturbance of the brain. 4. Assessment of the blood vessels supplying the brain In the case of a suspected cerebral haemorrhage, a stroke, or a malfunction of the cerebrovascular circulation, a so-called CT angiography may be performed. This allows for a better a representation of the brain's blood vessels with the aid of a contrast agent. 5. The exclusion of a brain tumour or a brain malformation A CT can be performed with or without a contrast agent in the case of a suspected tumour or a malformation of the brain. In this case, magnetic resonance imaging is another important method. 6. Planning of surgical treatment, interventional treatment or radiotherapy 7. For a follow-up examination of known changes in brain, vessels and skull bones 8. Investigation of reduced hearing ability: Disorders in the temporal bones, which are on the side of the skull, can lead to a reduction in hearing ability. Procedure Persons You will be looked after by an experienced team consisting of a medical radiology technichian (MRT) and a radiologist. In addition, you will also be observed from the switch-room via a monitor. A contrast agent, as well as any necessary drugs, will be administered via a cannula in the forearm before the examination by the radiologist or an experienced MRT. After the computer has generated the images, the radiologist will analyse them and the results are either handed to you or sent to the doctor who referred you. Preparation
. Normally, you may eat a light meal before the CT. Do, however, verify this at the time of making the appointment. 2. You should take your usual daily medication with some liquid in the morning. 3. If you are a diabetic, please ask your doctor how you should take your medication on the day of your procedure. If you think that your blood sugar levels are low, please inform the MRT immediately. 4. Before the procedure, please tell the radiologist about all medication you are taking. 5. Please bring up-to-date lab results with you (no more than 7 days old), Please ask which results are needed when making the appointment. 6. Please remove all metallic objects such as jewellery, glasses, hairpins and clips. If necessary, please also remove dental prostheses and hearing aids before the procedure. 7. Be certain to inform the CT team and the radiologist about any existing allergies or intolerances to contrast agents. With appropriate preparation, the procedure can be carried out in most cases. Precautions Please inform your doctor in advance if one of the following conditions applys or could apply to you:. Pregnancy: If you are pregnant, this examination may NOT be carried out, except in a life-threatening situation that makes an immediate CT examination necessary. 2. Allergy to iodine: If you have ever had an allergic reaction to iodine, there is a high risk associated with administering these substances again. However, if the allergic reaction was only minor, it is possible to minimise the risk of a further allergic reaction by administering an appropriate drug. Please contact the doctor who referred you before the procedure. 3. Diabetes mellitus: If you are a diabetic and need medication daily, please clarify with your family doctor before the procedure which medicines you should stop taking before/after the CT. 4. Thyroid gland disorders: If you suffer from an untreated hyperthyroidism (hyperactivity of the thyroid gland), then the contrast agent can cause a state of shock (thyrotoxic crisis). We therefore ask you to clarify this with your doctor beforehand and to treat this condition with medication. Then there will be no increased risk. 5. Kidney disorder: If you suffer from renal impairment, your laboratory results will determine whether or not you can be given a contrast agent. Otherwise your kidneys must be protected from further damage through special preparation (infusion). Please discuss this beforehand with the doctor who referred you. Duration The entire procedure including preparation takes about 0-5 minutes. As in all medical facilities, your examination may be delayed should an emergency patient be given priority. Please always allow sufficient time in your planning. Process Before the procedure, you will usually be given an information sheet and a questionnaire, which, among other things, contains questions about existing diseases, medication taken currently, and specific questions regarding intolerances to contrast agents or iodine. If you should have additional questions or considerations, please consult the MRT or the responsible doctor. Before the start of the procedure, you will lie down on the examination table of the CT scanner. If necessary, a vein cannula is inserted
and connected to the contrast agent system. Then the examination table is moved into the tube. The staff must now leave the room but they can hear you via a loudspeaker and see you by means of a camera. The painless procedure begins and takes only a few minutes. It is of great importance that you follow the instructions from the loudspeaker regarding your breathing as exactly as possible. If you are given contrast agents, this may cause a temporary hot sensation in the entire body and a metallic taste in the mouth. This is completely normal so you need not be concerned. When the examination is over, you will be asked to take a seat in the waiting room for a period of observation. The doctor/mrt checks the images and removes the vein cannula after 20 minutes at the latest. Then you can go home. You will be given the results after the evaluation is complete or it will be sent to the doctor who referred you. After procedure You will usually be able to go straight home after the procedure. Please tell an MRT immediately if you feel dizzy or sick. They will advise you to remain still until the symptoms improve, or for at least 30 minutes. In certain cases you may also be given medication to deal with the nausea. If you have come by car, please check with the medical staff after the procedure whether you have been given any medication which might affect your concentration and prevent you from driving home by car. You are asked to drink a lot during the course of the day so that the contrast agent leaves the body as rapidly as possible. Consideration Risks The CT is a very low-risk procedure. An intolerance reaction to contrast agents is very rare. You may develop a rash and/or itching in such cases. The symptoms are usually only short-lived and disappear of their own accord. If necessary, medication may also be administered in the form of so-called antihistamines. On extremely rare occasions, severe allergic reactions (anaphylactic shock) may occur, accompanied by breathing and circulation problems and/or loss of consciousness. This can be a life-threatening reaction, depending on its severity, and requires immediate medical attention. CT uses X-ray radiation. To ensure your safety, the X-ray level is reduced to a minimum. However, as X-rays can damage unborn life, this procedure is generally not carried out if you are pregnant. Only in the case of a life-threatening emergency, where an MRI is not available and the clinical situation demands immediate action, a CT may be performed. Alternatives MRI (magnetic resonance imaging) is an alternative to CT. MRI is primarily carried out on children because of the absence of radiation exposure. Despite its longer duration (about half an hour to hour) and its elaborate examination procedure, it is an alternative examination method to CT for the examination of the brain. A CT examination of the skull is inferior to an MRI in many ways in terms of sensitivity, as the brain can be visualised much more precisely with MRI. For diagnostic tasks concerning a bone fracture, the CT is clearly superior to the MRI. What is best in cases of bleeding is, as of yet, under discussion. FAQ
Can I have a computed tomography if I am highly claustrophobic? Yes. The gantry of the CT is considerably less tight and narrow than the tube in MRI, so feelings of claustrophobia rarely arise. In a CT, the patient lies on the examination table, which moves through a narrow "ring" (gantry, see Figure X). You always have a clear view of the examination space, and the staff can see and hear you at all times. Should a computed tomography of the skull be performed as a screening test like a blood test, for example (once a year)? No. This procedure is not suitable for use as a preventative measure. It should only be performed if certain conditions are fulfilled and your doctor feels that it is justified. Do I have to be an in-patient in the hospital to have a computed tomography? No, the procedure can also be performed if you are an out-patient. You can go home again afterwards unless there are other medical reasons why you should not do so. Which patients should not undergo this procedure? Patients with a strong allergy to contrast agents are at high risk of a critical incident. The procedure should only be performed after appropriate preparation and in the case of a life-threatening condition where CT can provide important information. Usually, this will only be performed in a hospital. What do I need to bring with me? Please clarify when making an appointment whether you must bring current laboratory results (e.g. kidneys and thyroid gland values, or blood coagulation parameters). Is there a weight limit for a computed tomography? Yes. Please report your weight at the time of registration if you weigh more than 50 kg, since different CTs have different weight limits. Can I have a computed tomography during the pregnancy/nursing period? During pregnancy, there is the danger of injury to the embryo/foetus caused by radiation exposure. Therefore, this examination should only be performed if the mother suffers from a life-threatening disorder. With patients who are breastfeeding, the decision should also be made according to urgency, and alternative procedures should be given preference. If contrast agents were administered, it is recommended not to breastfeed for one to two days and to dispose of the mother's milk during this time, since the contrast agent also reaches the milk. How much radiation will I be exposed to? The radiation exposure for one skull CT amounts to about 2 msv. This corresponds to a natural radiation exposure of approximately 8 months. Citations - Team General Hospital Vienna