When should CT be performed in children with lung disease?

Computed tomography (CT) can provide invaluable information in many paediatric chest diseases and is the most sensitive way of imaging the lungs due to its high spatial resolution. With the advent of multidetector CT, high-speed isotropic imaging allows superb visualization of the tracheobronchial tree and, following the administration of intravenous contrast, of the pulmonary and systemic circulation, allowing even small vessels to be visualized and in some cases negating the need for conventional (more invasive) diagnostic angiography. However, the radiation burden delivered by CT is the largest of any imaging modality, and it is well established that the lifetime cancer mortality risk as a result of radiation exposure is higher in children than in adults. It is essential, therefore, that indications for CT are restricted to those that are of real diagnostic benefit, and that the radiation dose is kept to a minimum. We discuss the indications for CT in paediatric respiratory disease and the optimal use of the different types of CT scan available.