MRI, CT

Question

Why do people with CF need a CT or MRI scan? What are the pro’s and con’s. Especially with regards to children.

Answer

Dear ECORN user
Thank you for this interesting question.
In patients with CF, a close follow-up of the lung status is important so that the treatment can be adapted if needed. This follow-up takes into account the symptoms (cough, sputum, etc…) and the course of lung function (spirometry). Indeed, the airway obstruction will increase with increasing lung infection and this is measured by lung function. Lung function can be measured reliably from the age of 6 years on. However, in recent years, lung function is no longer sufficiently sensitive. Thanks to the current treatment modalities, lung function will remain stable and even be normal in many children with CF. Therefore an extensive search for sensitive indices that reflect the state of the lungs has been ongoing. This is not only important in daily routine but also to evaluate the effect of new medicines that become available for the treatment of CF.
In this way, imaging of the lungs has become an important tool. A routine chest X-ray or radiograph can indicate important zones of lung infection but a chest CT scan gives a much more accurate image because the lung can be visualizedin three dimensional. The chest CT is often abnormal whereas spirometry is still normal. Spirometry can remain stable while new areas of damage or infection can been seen on chest CT. The disadvantage of chest CT is the cost and radiation exposure. Although new imaging techniques have substantially decreased the radiation dose, a CT cannot be done with the same frequency as for instance lung function. An MRI scan uses magnetic fields and does not use radiation. This technique is ideal to visualize the brain but the accuracy for the lungs is much less because they contain air. Still, in CF it has been evaluated whether MRI could possibly replace chest CT to document lung disease severity. Especially in Germany there is quite a bit of expertise with this technique. The disadvantage of MRI is that the apparatus is very expensive and not available in many sites. Also for MRI the child needs to pass through a closed tunnel and the machine is very noisy. The child has to be able to lie still for 20 minutes. This means that young children need to be sedated or need to undergo general anesthesia to have this test done. For chest CT it is usually possible to do the test without any sedation from the age of 3 years on. In some centres a volume controlled CT is done. In that case a young child needs to be put to sleep and needs to be intubated.
We hope that this is a sufficient answer to your question.
Prof. Kris De Boeck

02.05.2012