Finding the right tests…
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Finding the right tests…
CT Scan
A CT head scan takes cross-sectional X-ray images of your brain, skull, and the fluid spaces inside your head. Your doctor may order it after a fall or blow to the head, for a sudden severe headache, sudden weakness or slurred speech, or fainting spells that need an explanation. The scanner rotates around you while you lie still on a table, and a computer builds detailed slice images a radiologist can review. It can be done with or without injected contrast dye, depending on what your doctor is checking. Most head CT scans finish within a few minutes once you are positioned on the table.
This scan itself doesn't measure a lab value. A radiologist reads the images for signs of bleeding, swelling, a mass, or bone injury, and writes a report your doctor uses to decide next steps. There's no single number or typical range here, since the finding is written up as a description.
A head CT uses X-rays taken from many angles around your skull. A computer combines them into cross-sectional images, like slices of bread, so a radiologist can look at your brain tissue, the bone around it, and the spaces where fluid normally flows.
- Head injury, especially with loss of consciousness or ongoing confusion - A headache that comes on suddenly and feels like the worst you've ever had - New weakness on one side, trouble speaking, or a change in alertness - Follow-up after a stroke, or to check for a bleed before starting blood-thinning medicine
Many head CTs are done without any injected dye, especially in an emergency, because fresh bleeding and skull fractures show up clearly without it. If your doctor suspects a tumor or infection, contrast dye may be added partway through the scan to make blood vessels and abnormal tissue stand out more.
A CT head scan does not look at soft brain detail the way an MRI can. Your doctor may still order an MRI afterward if the CT is unclear or if a more detailed look at brain tissue is needed.
Only if contrast dye is planned, since your stomach needs to be mostly empty for that. For a plain scan without dye, you can usually eat and drink as normal, but ask the centre when you book so you know what applies to your appointment.
Not always. Many head CT scans are done without any contrast, especially for trauma or a suspected bleed. Your doctor decides based on what they're looking for, and the centre will confirm before your scan.
The actual scanning is quick, often just a few minutes once you're positioned on the table. Getting ready, and waiting if contrast is used, adds some time on top of that.
A head CT uses a small dose of ionizing radiation. RadiologyInfo.org notes that when only the head is scanned, there is no radiation dose to a fetus, but tell the technologist if you might be pregnant so the right precautions are taken.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
If no contrast dye or sedation was used, most people can drive themselves home right after. Ask the centre directly if you're unsure, since your situation may be different.
A head CT can show bleeding and larger areas of stroke damage, and it's often the first scan used to rule out a bleed before stroke treatment starts. Some early or small strokes are easier to see on MRI, so your doctor may order both.
Bring any previous head scan reports or films if you have them, and a list of your current medicines. If you've had a reaction to contrast dye before, tell the staff when you arrive.