Imaging of community-acquired pneumonias

Community acquired pneumonia (CAP) are acute pulmonary infections that take place in not hospitalized persons. Chest x-ray examination is the first diagnostic tool because it allows to confirm or to exclude the pneumonia, to narrow the differential diagnosis, to indicate other assessments or to follow the evolution of the pneumonia. Based on the aspect of the infiltrate at the chest x-ray we distinguish lobar, lobular, interstitial and nodular pneumonia. CT is indicated in doubt cases, in the survey of the complications and in persistent pneumonia, moreover the “tree in bud” pattern allows to help in the differential diagnosis. Recent studies have moreover demonstrated that MRI can have an important role in the early diagnosis of the necrotizing pneumonia.