The CT scanner is a large doughnut-shaped machine. A CT scan of the head can help find the cause of symptoms that may mean you have a brain injury or bleeding inside your head. It can also find a tumour and damage caused by a stroke and help find the best treatment for the cause of a stroke.
Talk to your doctor about all your health conditions before the test. For example, tell your doctor if:. The test will not cause pain, but some people feel nervous inside the CT scanner. If a medicine to help you relax sedative or dye is used, you may feel a quick sting or pinch when the IV is started.
The dye may make you feel warm and flushed and give you a metallic taste in your mouth. Some people feel sick to their stomach or get a headache. Tell the technologist or your doctor how you are feeling. Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems.
It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.
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Please turn on JavaScript and try again. Important Phone Numbers. Topic Contents What is it? Why is this test done? Another use of brain CT is to provide guidance for brain surgery or biopsies of brain tissue. You may want to ask your doctor about the amount of radiation used during the brain CT procedure and the risks related to your particular situation. You should keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor.
Pregnancy : If you are pregnant or suspect that you may be pregnant, you should notify your doctor. Radiation exposure during pregnancy may lead to birth defects.
If it is necessary for you to have a CT of the brain, special precautions will be made to minimize the radiation exposure to the fetus. Contrast media: If contrast media is used during a brain CT, the patient may develop an an allergic reaction to the media. Some patients should not have an iodine-based contrast media. Patients who are allergic to or sensitive to medications should notify their doctor. When you schedule your brain CT scan, you should inform the access center representative if you have had an allergic reaction to any contrast media or if you have kidney failure or other kidney problems.
IV contrast will not be administered if you have had a severe or anaphylactic reaction to any contrast media in the past. You may be able to have the scan performed without contrast media or have an alternative imaging exam. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.
Nursing mothers may want to wait 24 hours after contrast material is injected before resuming breastfeeding. Diabetes: Patients taking the diabetes medication metformin Glucophage should alert their doctors before having an IV contrast injection as it may cause a rare condition called metabolic acidosis.
If you take metformin, you will be asked to stop taking it at the time of the procedure and wait 48 hours after your procedure before restarting this medication. A blood test to check kidney function may be required before you can resume taking metformin. There may be other risks depending on your specific medical condition.
Be sure to discuss any concerns with your doctor prior to the procedure. If you are having computed tomography angiography CTA , you will be given specific instructions when you make your appointment. The following instructions will help you prepare for your brain CT:. Clothing : You may be asked to change into a patient gown. If so, a gown will be provided for you. Please remove all piercings and leave all jewelry and valuables at home.
Contrast media: You will be asked to sign a consent form that will detail the risks and side-effects associated with contrast media injected through a small tube places in a vein called an intravenous IV line.
The most common type of brain CT scan with contrast is the double-contrast study that will require you to drink a contrast media before your exam begins in addition to the IV contrast. If you had mild to moderate reactions in the past, you will likely need to take medication prior to the brain CT scan. Food and drink : If your doctor ordered a brain CT scan without contrast, you can eat, drink and take your prescribed medications prior to your exam.
If your doctor ordered a CT of the brain with contrast, do not eat anything three hours prior to your brain CT. You are encouraged to drink clear liquids. Diabetics : Diabetics should eat a light breakfast or lunch three hours prior to the scheduled scan.
Depending on your oral medication for diabetes, you may be asked to discontinue the use of your medication for 48 hours after the brain CT scan. If you have a CT scan with Johns Hopkins radiology, detailed instructions will be given following your examination.
Medication : All patients can take their prescribed medications as usual, unless otherwise directed. Based on your medical condition, your doctor may request other specific steps for brain CT preparation.
Brain CT scans may be performed on an outpatient basis or as part of your hospital stay. You may be told to hold your breath for short periods. Certain CT exams require a special dye, called contrast material. It is delivered into the body before the test starts. Contrast helps certain areas show up better on x-rays.
If you weigh more than pounds kg , find out if the CT machine has a weight limit. Some machines do. The x-rays produced by the CT scan are painless. Some people may have discomfort from lying on the hard table. CT scans use more radiation than regular x-rays.
Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your provider should weigh this risk against the benefits of getting a correct diagnosis for a medical problem. Some people have allergies to contrast dye. Let your provider know if you have ever had an allergic reaction to injected contrast dye.
In rare cases, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, tell the scanner operator right away. Scanners come with an intercom and speakers, so someone can hear you at all times.
A CT scan can reduce or avoid the need for invasive procedures to diagnose problems in the skull.
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