A CT scan combines X-ray and computer technology to create detailed images of your organs and body structures. Doctors use these images to diagnose your condition or plan treatment.

To get the images, you lie inside a CT scanner. CT stands for computed tomography.

When you have a CT at OHSU, you’ll find:

• Quick scheduling
• Fast results
• State-of-the-art equipment
• Complex scans that aren’t widely available
• A team that puts your safety and comfort first

Before your appointment

We usually schedule you for a 30- to 60-minute appointment. We offer weekday and weekend appointments.

Once your scan is scheduled, you’ll get instructions through MyChart on how to prepare. Depending on your scan, you may need to stop eating and drinking for several hours. Please follow instructions or we may have to reschedule your appointment. If you have any questions, please call us at 503-418-0990.

If you’re anxious about being in the scanner, you can ask your doctor to prescribe medication to help you relax. In that case, please bring someone to drive you home.

Let us know if you:

• Are unable to lie still for more than a few minutes.
• Are pregnant or think you may be pregnant.
• Are breastfeeding.
• Have a kidney condition.

You may be given a substance called contrast by IV or to drink. Contrast helps organs and tissues stand out on imaging. Some people may have a mild allergic reaction to contrast. If this happens, we will assess your symptoms and give you medication if needed. You can ask to do your scan without contrast. We will assess your condition and speak with a doctor about the need for contrast.

You’ll be scanned while lying on a table that moves in and out of a tunnel-shaped scanner. We have cushions for your comfort.

Scans are painless and take five to 25 minutes. You can talk to us, and we’ll check on you often. If you feel stressed, you can ask to stop. We’ll check the images for quality and see if we need more. We can schedule you for another scan if needed.

How CT works

An X-ray beam scans an organ or system from different angles. A computer combines the scans into 3D images.

After your appointment

You may eat and drink as usual. If you’ve had contrast, drinking extra water will help flush it out.

You’ll get your results through MyChart, usually within 24 hours. If you’re having a complex scan, results may take longer because we need more time to process the images.

Types of CT scans

CT perfusion: This checks how well blood is flowing to your brain.

CT TAVR: This checks your heart and vessels. It also checks the aortic valve as part of treatment planning before a heart valve replacement.

How much radiation am I getting?

It depends on the type of scan. Radiation doses range from about 2 to 20 millisieverts (mSv). For comparison, sun exposure and other forms of radiation in the environment expose humans to about 3 mSv each year.

We use the lowest possible dose to get a diagnosis for each patient.

What’s the difference between CT and MRI?

A CT scan uses an X-ray beam that emits a small amount of radiation. A CT is much quicker and quieter than an MRI. A CT is typically better for seeing the structure of bones and organs.

An MRI scan uses magnets and radio waves but not radiation. An MRI takes longer than a CT and can detect things that CT can’t. An MRI is typically better for seeing differences between normal and abnormal tissue.

Which one your doctor recommends will depend on your past imaging, your condition and which scan offers more benefit than risk.

Can a CT scan detect cancer?

Yes. CT scans can show tumors, their size, and whether and where they have spread.

We also use CT scans to assess response to treatment and to look for other anomalies.