Gain or damage by CT scan

Question

What is the indication to do a CT scan in a 2-year old child with CF? What can we decide from that?

Answer

Dear questioner,

In the disease cystic fibrosis chronic bronchitis or lung infection can occur from early age on. Most of the time it concerns slowly evolving infections. Many young children will have very little symptoms. Often the doctors who listen to the chest will hear no abnormalities despite the fact that there is nearly always infection present.

An important tool to follow the disease course is lung function. This test can only be done reliably from the age of 5 to 6 years. In addition we know that in young children the lung function test will remain normal despite the fact that infection is present. At times you can see signs of lung infection on a standard chest X-ray, but in many children the disease severity is better picked up and quantified by a CT scan of the lungs. Many studies have informed us that half of the children will have already dilated (abnormal) airways by the age of 5 years. And these changes on the CT scan worsened despite the fact that the lung function remains stable. A CT scan is thus an important tool to document lung disease severity and adapt treatment intensity. The problem with CT scan is however that it has a relatively high radiation dose, especially when compared to standard chest X-ray. The younger the child, the more important the radiation burden. New protocols are however available that decrease the radiation burden. One can state that one chest CT done on the latest machines is about equivalent with the radiation that a person is exposed to during one transatlantic flight. Nevertheless, it remains important to limit the number of CT scans in the same person to avoid radiation burden. In many CF centres a CT of the chest will be done 2-yearly from the age of 5 years on.

In the meantime the search for sensitive instruments without radiation burden continues. One of the possibilities is an MRI scan. The biggest disadvantage is that the lung image obtained with this technique is less accurate. There are also practical problems such as MRI scans are much less available than CT scans, it is a noisy apparatus and some children are really afraid of this exam.

To conclude a CT scan of the lungs is a very useful tool in the follow up of children with cystic fibrosis. There is no consensus as to whether all children should have a CT scan and with which frequency. The search for tests with less radiation burden continues.
Prof. Kris De Boeck

08.05.2012