It is best for people at risk to have CT once a year Ordinary lung X-ray is almost impossible to detect early lung cancer below 1 cm, and most of the lung cancers that can be detected by such examination are already in the middle and late stages. To detect early lung cancer, it is still necessary to rely on CT. Studies show that the chance of detecting early lung cancer by CT is about 24%, while that by X-ray chest film is only 6.9%. However, because CT is expensive and has certain radiation, it is not suitable as a routine screening program on a large scale, so experts generally recommend that people over 40 years old who are at high risk of lung cancer, smoke and have a family history of cancer should have a low-dose lung CT once a year. If “hairy glass” is found in the lungs on CT, it is likely to be a sign of early lung cancer. However, since it takes 7 to 8 years for some people to develop from “hairy glass” to true early stage lung cancer, it requires careful judgment by doctors whether to operate to remove it or not.