More comprehensive than an x-ray, computerized tomography or CT brain scan can be ordered for numerous reasons. If you are about to get a CT to scan your head, how should you prepare and what should you expect?
The details about CT scans
The CT scan creates a composite of a patient’s brain by taking a series of x-rays, that is later assembled by a computer. Looking at the image of a brain can help a doctor determine the correct course of treatment. Developed by British engineer Godfrey Hounsfield of EMI Laboratories, England, and by South Africa-born physicist Allan Cormack of Tufts University, Massachusetts, in the early 1970s, the first CT scanner took hours just to get enough data for a single scan. It then took several days to reconstruct it. Today an entire chest CT scan requiring 40 scans (or eight mm slices) can be done in under ten seconds. Still, the first CT scan was noteworthy. It correctly identified a woman’s brain tumor. It also earned the pair a Nobel Prize in 1979 in Physiology and Medicine. Two years later, Hounsfield was even knighted. EMI Laboratories benefited from its record label’s success with British pop band The Beatles; some profits from music were put into development of the CT scan.
CAT or CT scan?
Although there is some confusion between a CAT scan (computed axial tomography) and a CT scan, the two terms refer to the same diagnostic tool. In its early days, it was called an EMI scan (after the developing company), before being called a CAT scan. Today, CT is the preferred term –– perhaps because some felt it was derogatory toward felines or too many patients were mistakenly visiting veterinarians! Regardless, getting a CT brain scan is considered safe and effective. Still, it delivers several more times the amount of ionizing radiation than you would get from an x-ray. Made up of high-energy wavelengths which can penetrate your body’s tissue, ionizing radiation can lead to DNA mutations that can cause cancer years later.
However, the amount you will receive is considered quite small (although with some larger CT scans, the radiation dose falls in the range associated with increased cancer risk.) Remember that you get a small amount of ionizing radiation every day from the sun and the breakdown of uranium in things like soil or building materials. Since 1980, per-capita radiation exposure has doubled; medical imaging from x-rays and CT scans are believed responsible. If you are pregnant, a CT scan may not be worth the risk. For those with a BMI over 25, the radiation dose –– particularly for scans below the neck –– is higher. It is also riskier for children. However, for most patients, not getting a CT to scan your head is riskier than getting one since the symptoms that lead a health care provider to recommend the diagnostic tool can indicate a condition that is far more dangerous than a minute dose of radiation.
When is a CT scan prescribed?
Symptoms that warrant a CT scan include persistent headaches, seizures, difficulty speaking, or fainting spells. If you’ve suffered head trauma recently, your doctor may also prescribe a CT scan. The scan can help diagnose a brain tumor, stroke, birth defects, and numerous other medical concerns. It can also help your doctor evaluate your skull, sinuses, and brain along with planning radiation therapy. When you arrive for your scan, you will most likely be asked to disrobe and don a hospital gown. If you are wearing a bra with a metal underwire, you should remove it. You should also remove anything metal above your neck that is removable, such as jewelry. This includes piercings, dentures, eyeglasses, and bobby pins or other hair accessories. People with claustrophobia often have anxiety within the device, as do small children. Your health care provider can offer a sedative. Since the interior of the machine is similar to a coffin, even people who don’t panic in enclosed spaces often feel uncomfortable.
To take a CT scan of your head, you will be asked to lie down on a small examination table that slides into the tunnel of a machine shaped like a donut. Once inside, an x-ray tube and electronic x-ray detectors will rotate around you. In a control room, the technologist operating the scanner will be able to see you and communicate via a microphone. During the process you will be expected to be motionless, as movement can blur the images.
If your health care provider is concerned about your blood vessels, you may be administered contrast dye via an intravenous line inserted into a vein of your arm or hand. You will be asked to abstain from food and drink for several hours prior to the procedure. Make sure to let your doctor know if you have diabetes, heart disease, asthma, kidney disease, or thyroid problems. All of these can be affected by the dye. If you are allergic to the dye, your doctor may prescribe a steroid. A small percentage of people have mild side effects from the dye including a rash and a persistent metallic taste which lasts an hour or so. The procedure itself is usually completed in fifteen minutes.
Results
The CT brain scan creates cross-sectional images like slices of bread reassembled into a loaf. It can even create three-dimensional images which can be viewed on a computer monitor. It can be printed on film or by a 3D printer or transferred to a CD or DVD. A radiologist will examine the scan and consult with your health care provider. You will then learn the results and treatment options if warranted.
Written by John Bankston