CT Scan – Chest

About a CT scan of the chest

A chest CT (computed tomography) scan uses X-rays and a computer to make detailed cross-section pictures of the inside of the chest, including the lungs, airways, heart, major blood vessels, the lymph nodes in the middle of the chest and the bones of the chest wall. It shows far more detail than a chest X-ray and is the main scan for the lungs.

A chest CT may be used to investigate:

• an abnormal chest X-ray, or symptoms such as a persistent cough, coughing up blood, breathlessness or chest pain
• suspected lung cancer, and whether a cancer has spread
• lung nodules (small spots on the lung), including checking them over time; most are harmless
• long-term lung conditions such as bronchiectasis, emphysema and pulmonary fibrosis, often using a detailed technique called high-resolution CT (HRCT)
• enlarged lymph nodes, infections that are not getting better, and problems with the chest wall

For suspected blood clots in the lungs, a different scan, a CT pulmonary angiogram (CTPA), is used, and blood clots need urgent hospital care. If you are aged 55 to 74 and smoke or used to smoke, you may be invited for a free NHS lung health check, which can include a low-dose CT scan. You can read more in our article on CT scans of the chest.

What happens during the scan

You lie on your back on the scanner bed with your arms raised above your head. The bed moves through a short, open ring while your chest is scanned. The radiographer controls the scanner from the next room, but can see, hear and talk to you throughout. You will be asked to take a breath in and hold it for a few seconds; for some lung scans, you may also be asked to breathe out and hold, or lie on your front. Some chest scans use an injection of contrast dye to show the blood vessels and lymph nodes.

For some CT scans, an injection of contrast dye is given through a small cannula in a vein, usually in your arm or hand, to make blood vessels and organs show up more clearly. CT contrast contains iodine. As it goes in you may feel warm and flushed, notice a metallic taste, or feel as if you are passing urine; these feelings pass within a minute or two. Allergic reactions are uncommon, and you may be asked to wait for up to 30 minutes afterwards. Where contrast is needed, it is charged separately.

Is CT safe?

CT uses X-rays, which are a type of ionising radiation. A CT of the chest gives a typical dose of about 8 mSv, similar to the natural background radiation you would receive from the environment over about 3.6 years. Low-dose techniques, used for checking lung nodules, give much less. The risk from a single scan is very small, and every CT scan is checked by a radiologist or radiographer to make sure the benefit of the scan outweighs the risk, as required by the Ionising Radiation (Medical Exposure) Regulations. If you have had other CT scans recently, tell us when you book.