Low-dose CT lung scan: what to expect
A lung cancer screening scan is a low-dose CT (LDCT): painless, a few minutes on the table, no injection, repeated once a year while you qualify. Most findings are not cancer, but some need a follow-up scan. Your doctor explains your results and decides what comes next. (ACS, 2024) (USPSTF, 2021) (RadiologyInfo, 2024)
Who gets the scan
The USPSTF recommends a yearly low-dose CT for adults 50 to 80 with a 20 pack-year smoking history who smoke now or quit within the past 15 years (grade B), and says to stop once a person has not smoked for 15 years. It advises shared decision-making before screening. (USPSTF, 2021) Check your pack-years with the pack-year calculator; full details are on lung cancer screening.
During the scan
- No contrast, nothing to swallow and no injection. (RadiologyInfo, 2024) (ACS, 2024)
- You lie on your back on the CT table, usually with your arms raised over your head; straps and pillows may help you keep still. (RadiologyInfo, 2024)
- The table moves slowly through the scanner while you hold your breath for each short scan of 5 to 10 seconds. (RadiologyInfo, 2024)
- The scan takes a few minutes; the whole visit can take up to half an hour. (ACS, 2024)
- The x-rays do not affect metal parts in your body, such as pacemakers or artificial joints. (RadiologyInfo, 2024)
Radiation, in plain words
The dose is less than a standard CT scan but more than a chest x-ray, and follow-up scans add more. (ACS, 2024) RadiologyInfo says LDCT uses up to 90 percent less radiation than a conventional chest CT, and no radiation stays in your body after the exam. (RadiologyInfo, 2024) The NCI notes that radiation from screening may raise cancer risk, and that younger people and people at low risk are more likely to be harmed by it than helped, which is one reason screening is for people at high risk. (NCI, 2024)
Your result and Lung-RADS
The American College of Radiology created Lung-RADS to standardize how screening scans are reported; it guides which findings are suspicious for cancer and how lung nodules are followed up, and its use may lower false-positive results. (USPSTF, 2021) Categories run from 1 (negative) to 4X (suspicious), based mainly on nodule size and appearance. (Biomedicines, 2025) Your report names the category, and your doctor tells you what it means for you and when your next scan is. Each category, its usual next step and nodule sizes: lung cancer screening results.
If the scan finds something
- Most lung nodules, more than 95%, are not cancer. A nodule above a certain size usually means a follow-up LDCT several months later to see whether it changes. If it grows or looks suspicious, your doctor may suggest a CT with contrast or a biopsy. (RadiologyInfo, 2024)
- A false-positive result can cause worry and lead to more tests, such as a biopsy, which has its own risks; a lung biopsy can cause part of the lung to collapse. (NCI, 2024)
- Screening should be done at a facility with the right scanner, experience in LDCT screening and a team to follow up abnormal results. (ACS, 2024)
More: after an abnormal screening result and false positives and overdiagnosis.
Every year, and quitting
The scan is repeated every year while you meet the criteria. (USPSTF, 2021) Screening is not a substitute for quitting: people who smoke should be offered help to stop, and quitting lowers the risk of getting and dying from lung cancer. (ACS, 2024) More: help to quit smoking.
What it costs
Medicare Part B covers one screening scan a year for people 50 to 77 who have no symptoms, smoke now or quit within the last 15 years, have at least a 20 pack-year history and have an order from their provider. Before the first scan you need a visit to talk through benefits and risks. You pay nothing if your provider accepts assignment. (Medicare.gov) For private plans, see preventive screenings covered by insurance.
Questions people ask
How long does a low-dose CT lung scan take?
The scan itself takes a few minutes and is painless; the whole visit, including getting into place on the table, can take up to half an hour. You do not swallow anything or get an injection. (ACS, 2024)
How much radiation is in a low-dose CT scan?
Less than a standard CT scan and more than a chest x-ray. RadiologyInfo says it uses up to 90 percent less radiation than a conventional chest CT, and no radiation remains in your body afterward. (ACS, 2024) (RadiologyInfo, 2024)
Does a nodule on my scan mean I have cancer?
Usually not. RadiologyInfo says more than 95% of lung nodules are not cancer. A nodule above a certain size usually means a follow-up scan a few months later to check that it is not growing. Your doctor explains your result. (RadiologyInfo, 2024)
Does Medicare cover a lung cancer screening scan?
Yes, once a year if you are 50 to 77, have no symptoms, smoke now or quit within the last 15 years, have at least a 20 pack-year history, and have an order from your provider. Before the first scan you need a visit to discuss benefits and risks. You pay nothing if your provider accepts assignment. (Medicare.gov)