Computed tomography (CT or CAT) of the head is a special noninvasive X-ray scan used to detect and diagnose health problems in the brain. This test can be used to evaluate symptoms such as severe headache, dizziness, blurred vision, seizures, slurred speech and loss of balance. Head CT scan can detect bleeding, blood clots, tumors, brain injury, enlarged brain cavities (hydrocephalus) and malformations of the skull.
Your doctor may recommend a head CT if you have symptoms that could be caused by a brain disease or disorder. Disorders of the brain typically fall into several categories:
- Bleeding – This could be due to brain trauma, blood vessel damage, bleeding stroke, or aneurysm. Bleeding in the brain typically causes a severe headache.
- Blockage – Blood clots can block arteries and cause stroke symptoms.
- Tumors – Head CT is one of the best tests to detect brain tumors.
- Anatomic abnormality – This could be due to a tumor or hydrocephalus which is a condition that enlarges the normal cavities in your brain.
- Infection – Rare infections (abscesses) in the brain can be detected by CT scan.
Head CT may also be recommended when planning for brain surgery, radiation therapy or brain biopsy.
- Head CT scan is fast, noninvasive, accurate, and painless.
- Urgent medical conditions, such as stroke or bleeding aneurysm, can be diagnosed rapidly by head CT. The speed of the test can help doctors make critical decisions that save lives.
- In a single scan, head CT can evaluate bone, soft tissue and blood vessels.
- Unlike MRI, if you have metal in your body (shrapnel, bullets, needles, etc.) or an implanted medical device, you can still have a head CT since no magnets are used in the procedure.
- X-rays used in CT scans have no immediate side effects and do not remain in the body.
- Excessive radiation can increase the risk for cancer. However, the amount of radiation received from head CT alone is unlikely to cause cancer or increase cancer risk significantly.
- Pregnant women should be aware of the risk of radiation to the developing child. However, the radiation exposure to an unborn baby from a mother’s head CT is minimal and proper precautions are taken to protect the mother and baby. For more details, please refer to the section What if I am pregnant? Can I still have a CT scan? below.
- The ACR states that current information suggests breastfeeding is safe after the use of intravenous contrast. Please discuss your breastfeeding options with your medical provider.
- The risk of negative side effects due to contrast are rare. Refer to the About CT Contrast section for more details about the risks of different types of contrast.
If you are, or think you are pregnant, be sure to notify your doctor or technologist before undergoing a CT scan. The amount of radiation received during a CT scan is unlikely to harm you or your baby. However, in general, CT scans are not recommended in pregnant women. In every case, the mother’s health must be considered as well. The benefit to the pregnant woman of having the CT scan to diagnose an illness may outweigh the small amount of risk to the baby from a low-dose CT scan.
The part of your body being scanned should also be considered. For example, brain CT exposes the unborn baby to little or no radiation. Even if the fetus is directly exposed to CT scan radiation (such as in CT scans of the abdomen or pelvis), the increased risk of developing cancer later in life is one in 1000. Some doctors may recommend another type of exam (ultrasound or MRI) to avoid exposing your baby to radiation.
The ACR states that current information suggests breastfeeding is safe after the use of intravenous contrast. Please discuss your breastfeeding options with your medical provider.
For more information on contrast, please see About CT Contrast.
- Head CT is available at multiple ARA imaging centers and takes a total of about 10 to 15 minutes.
- You may be asked to change into a hospital gown, however, for head CT this may not be necessary.
- Since metal can distort the CT images, all metal objects and jewelry should be removed prior to the procedure. This may include hearing aids, removable dental prostheses, eyeglasses, piercings, hairpins, etc.
- The CT scanner is a large box shaped machine with a large hole in the middle.
- You’ll be placed on a moveable exam table which may have straps or bolsters to help keep your head and body from moving. You will need to remain as still as possible so the images will be clear.
- If your study requires intravenous (IV) contrast, your paramedic or technologist will place an IV line into your arm or hand to administer the contrast. IV placement may be uncomfortable and may cause bruising later. A saline solution drip may be used to help keep the IV line clear.
- The technologist will leave the CT scan room where you are and conduct the exam from a computer in a nearby room. You will be able to talk with the technologist at all times.
- The table will make a first quick pass through the scanner to set your body position. Next, the table will move your head through the scanner more slowly while the CT images are being taken. It may require several passes through the machine to complete the scan.
- You may hear slight buzzing, clicking, or rotating sounds during the scanning process.
- You may be asked to hold your breath during some parts of the scan. Breathing or any other movement can distort the images.
- When the scan is finished, you may be asked to wait a few minutes while the technologist checks the quality of the images. If needed, more images may be taken.
- Wear comfortable, loose fitting clothing. You may want to leave all jewelry, piercings and any other metal objects at home.
- If your exam requires contrast, you will be asked not to eat or drink for a few hours prior to the CT scan. In most cases, you should take all your medications as usual. Ask your doctor for specific directions about your daily medications.
- Be sure to tell your health care provider, ARA scheduler, and ARA technologist about any illness or allergies you may have. Health care providers should know if you have asthma, multiple myeloma, heart, kidney, or thyroid issues, or if you have diabetes. Also, provide a list of your current medications.
- Inform your radiologist if you are pregnant. Although the risk of brain CT is very low for the unborn baby, your doctor may choose an alternate exam. Depending on the circumstances, both the physician and patient may decide it is necessary to go ahead with the CT scan. Also, pregnant women should not receive IV contrast unless the benefits clearly outweigh the risks. For more details, please refer to the section What if I am pregnant? Can I still have a CT scan?
- Head CT is fast and painless. If you feel like you might be anxious during the exam, tell your scheduler. ARA technologists and our clinical staff are experts at helping people through CT exams with minimum anxiety.
- You can return to your normal activities after the exam. Drinking plenty of water will help flush the contrast agent from your system.
A radiologist, a physician specifically trained to interpret radiological examinations, will analyze the images and send a signed report to the provider who referred you to ARA. The physician will then share the results with you.