Low-Dose CT Scan


Low-dose computed tomography (also called a low-dose CT scan, or LDCT) is a non-invasive special kind of X-ray that uses a low dose (amount) of radiation to take multiple pictures as you lie on a table that slides in and out of the machine. A computer then combines these images into a detailed picture of your lungs. This procedure only takes 10 – 15 minutes and is not painful.  

Low-dose CT scan is, so far, the only recommended screening test for lung cancer. Studies on early detection of lung cancer found that lung cancer screening with LDCT can reduce mortality for those at high risk.


Who needs lung cancer screening with LDCT?

  • This screening is recommended for adults, be it male or female, aged 45 – 75, who are smokers or ex-smokers with a 20-pack-year or greater smoking history.
    • A pack-year is smoking an average of one pack of cigarettes per day for one year. For example, a person could have a 20 pack-year history by smoking one pack a day for 20 years or two packs a day for 10 years.
  • Other potential groups at risk who may benefit from the screening:
    • Repeated exposure to second-hand smoke
    • Parents or siblings or family members with lung cancer
    • Long-term exposure to cooking flames from coal or wood fumes, diesel gas, radiation


    What are the risks of lung cancer screening with LDCT?

    • False-positive results: A lung cancer screening test can suggest that a person has lung cancer when no cancer is present. Such results can lead to follow-up tests and surgeries that are unnecessary and may have more risks.
    • Overdiagnosis: A lung cancer screening test can find cases of cancer that may never have caused a problem for the patient. Overdiagnosis can lead to unnecessary treatment.
    • Radiation from repeated LDCT tests can cause cancer in otherwise healthy people.


    Therefore, lung cancer screening is recommended only for adults who are at high risk for developing the disease because of their smoking history and age, and who do not have a health problem that substantially limits their life expectancy or their ability or willingness to have lung surgery, if needed. Be sure to talk to your doctor first if you are thinking about getting screened for lung cancer.

    The best way to reduce your risk of lung cancer is to not smoke and to avoid second-hand smoke. Lung cancer screening is not a substitute for quitting smoking.


    When should lung cancer screening stop?

    Annual lung cancer screening should stop when you:

    • Turn 76 years old, or
    • Have not smoked in 15 or more years, or
    • Develop a health problem that makes you unwilling or unable to have surgery if lung cancer is found.


    What happens during lung cancer screening with LDCT?

    During the scan, you will be asked to lie flat on your back on a table that moves slowly into the CT scanner. The scanner is shaped like a ring and it rotates around a small section of your body as you pass through it.

    Specially-trained radiographers control the scanner from behind a screen in the CT room. You will be able to see and speak to them during the scan.

    When a scan is taken, you will need to lie still and follow simple breathing instructions for 10 seconds. This makes sure the pictures are not blurred.

    The scan is painless and you will be able to eat, drink or drive as normal after your scan.