The actual image capture during a low-dose CT scan takes less than a minute. You’ll hold your breath for roughly 15 to 20 seconds while the scanner captures detailed images of your lungs. The entire appointment, including check-in and positioning, typically lasts about 30 minutes.
What Happens During the Scan
You’ll lie flat on a narrow table that slides into a large, ring-shaped scanner. A technologist positions you with your arms raised above your head, then steps into an adjacent room to operate the machine. When the scan begins, you’ll be asked to take a deep breath and hold it while the table moves slowly through the ring. The X-ray tube rotates around you, capturing cross-sectional images of your lungs in a single pass. The breath-hold keeps your lungs fully inflated and still, which prevents blurring.
The image acquisition itself averages about 15 seconds for a standard scan and closer to 20 seconds when thinner, more detailed slices are needed. Most people find the breath-hold easy to manage. There are no needles, no contrast dye, and no sensation from the X-rays. You can breathe normally again immediately after the scan finishes, and you’re free to go right away with no recovery time.
Where the Rest of the 30 Minutes Goes
The bulk of your appointment is administrative. You’ll check in, confirm your information, and change into a gown if your clothing has metal zippers or snaps. The technologist will verify your identity, explain the process, and position you correctly on the table. A quick test alignment may be done before the actual scan. After imaging, the technologist checks that the images are usable before releasing you. All of this adds up to roughly 30 minutes total, even though the scanner itself runs for under a minute.
Radiation Exposure Compared to a Standard CT
A low-dose CT delivers about 1.5 millisieverts of radiation. That’s roughly one-fifth the dose of a standard diagnostic chest CT, which averages around 7 millisieverts. For context, 1.5 millisieverts is about 15 times more than a traditional chest X-ray, but still a small amount. It’s comparable to the background radiation you absorb naturally over about six months of daily life. The low dose is what makes this scan practical as a yearly screening tool, since the cumulative exposure stays modest over time.
How to Prepare
Low-dose CT scans require almost no preparation. You don’t need to fast, drink any contrast solution, or stop taking medications. Wear comfortable clothing without metal, or plan to change into a hospital gown. Remove necklaces and any jewelry that sits near your chest. The scan is painless, and you can drive yourself home and resume normal activities immediately afterward.
When You’ll Get Results
A radiologist reviews the images and sends a report to your ordering provider. If something needs immediate follow-up, you’ll typically hear back quickly. Otherwise, results come within a day to several days. It’s reasonable to ask your provider at the time of scheduling when you should expect to hear back, so you’re not left wondering.
Who Should Get Screened Annually
The U.S. Preventive Services Task Force recommends annual low-dose CT screening for adults aged 50 to 80 who have a smoking history of at least 20 pack-years and either currently smoke or quit within the past 15 years. A pack-year equals smoking one pack (20 cigarettes) per day for one year, so someone who smoked a pack a day for 20 years, or two packs a day for 10 years, both meet the threshold.
Screening stops once you’ve been smoke-free for 15 years or if a health condition makes lung surgery unlikely. If your initial scan is normal, the recommendation is to repeat it every year as long as you still meet the eligibility criteria. Most insurance plans and Medicare cover the screening without a copay for eligible individuals.