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Lung Cancer Screening: Low-Dose Spiral CT Scan

British Columbia Specific Information

Low dose computed tomography (CT) scans search the lungs for signs of lung cancer, as well as other lung diseases. Early detection using low dose CT scanning has been shown to reduce lung cancer deaths by 20%. The BC Lung Screen Trial provides the only access to organized lung cancer screening to eligible B.C. residents. Participants must be 55-80 years of age, be a current smoker or former smoker, and have smoked for 20 years or more. To learn more about the BC Lung Screen Trial program, see BC Cancer – The BC Lung Screen Trial and BC Cancer – Lung.

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.

Canadian experts recommend lung cancer screening every year up to three years in a row if: footnote 1

  • You are 55 to 74 years old.
  • And you have a smoking history of at least 30 pack years.
  • And you still smoke, or you quit within the last 15 years.

If you have a serious health problem, you and your doctor will decide if lung cancer screening is right for you.

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 jewellery, 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.



  1. Canadian Task Force on Preventive Health Care (2016). Recommendations on screening for lung cancer. Canadian Medical Association Journal, 188(6): 425–432. DOI: 10.1503/cmaj.151421. Accessed December 10, 2019.


Current as of:
November 4, 2020

Author: Healthwise Staff
Medical Review:
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine
Howard Schaff MD - Diagnostic Radiology