Lung Cancer Screening: Low-Dose Spiral CT Scan

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Test Overview

Screening tests help your doctor look for a problem before you have symptoms. Lung cancer screening is a way to find some lung cancers early, when a cure is more likely and when cancer is more treatable.

If your doctor recommends lung cancer screening, you'll have a low-dose computed tomography (CT) scan of your chest once a year. A special scanner called a spiral CT makes circular movements around your body. This doughnut-shaped machine sends low-dose X-rays, or radiation, through your chest to make detailed pictures. A low-dose CT uses much less radiation than a regular-dose CT scan. A doctor looks at the pictures of your lungs for growths, called nodules, that could be cancer.

Why It Is Done

Most people don't need routine lung cancer screening. It's only recommended for people who have a high risk for lung cancer.

Your doctor may recommend that you get screened each year if:

  • You are 50 to 80 years old.
  • And you have a smoking history of at least 20 pack years.
  • And you still smoke, or you quit within the last 15 years.
  • And you are in good health overall. Having a serious health problem might mean that you couldn't, or wouldn't want to, have treatment for lung cancer. The treatment could be too high-risk, and it might not help you live longer.

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

You may need to take off any jewelry, and some clothing, such as a bra. You will be given a gown to use during the test.

During the test, you will lie on a table that is attached to the CT scanner.

The table slides into the round opening of the scanner, and the scanner moves around your body. The table will move while the scanner takes pictures. You may hear a click or buzz as the table and scanner move.

It is very important to lie still during the test.

You may be alone in the scanning room. But a technologist will watch you through a window and talk with you during the test.

How long the test takes

The test will take about 30 to 60 minutes. Most of this time is spent getting ready for the scan. The actual test takes a few minutes.


How It Feels

The test will not cause pain.

The table you lie on may feel hard, and the room may be cool. It may be hard to lie still during the test.

Some people feel nervous inside the CT scanner. Tell the technologist or doctor how you feel.


  • Scans aren't perfect tests. They may not show lung cancer that is there. This is called a false-negative result.
  • The scan may show spots on your lungs that aren't cancer. This is called a false-positive result. This leads to more tests to make sure you don't have cancer.
  • Some screenings find lung cancers that wouldn't have needed treatment if they had not been found. This is called overdiagnosis. But because doctors can't tell which cancers will turn out to be harmless, most will be treated. This means that you may get treatment—including surgery, radiation, or chemotherapy—that you don't need.
  • Even though the dose of radiation for this type of CT scan is low, having this test each year increases your radiation exposure. There is a small chance of getting cancer from that extra exposure.
  • The scan can show problems in the chest that need more testing to confirm that they're not harmful. This is called an incidental finding.


Your doctor will likely get back to you with complete results in 1 to 2 days.

Low-dose CT scan to screen for lung cancer


No growths (nodules) were found in your lungs.

Next step: Another low-dose CT scan to screen for lung cancer in 1 year.


A nodule or nodules were found, but because of their small size, you don't need to do anything else right now.

Next step: Another low-dose CT scan to screen for lung cancer in 3 to 6 months.

A nodule or nodules were found, and at least one of them is large enough for your doctor to talk to you about having more tests now.

Next step: Your doctor may suggest any of these tests:

  • More scans, such as a CT scan or PET scan.
  • Bronchoscopy, which is a procedure that lets your doctor look into your airway.
  • Biopsy, which is the only way to diagnose cancer. In a biopsy, the doctor takes a sample of tissue from inside your lung so it can be looked at under a microscope.


Current as of: July 26, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.