Expiratory CT scan: When to do it and how to interpret it.

Expiratory CT scan is a complementary technique of inspiratory CT that provide valuable physiological information and may be more sensitive to detect air trapping than pul-monary function tests. It is useful in many obstructive airway diseases, including obliterative bronchiolitis, asthma, Swyer-James syndrome, tracheomalacia, hypersensitivity pneumonitis and sarcoidosis. In obliterative bronchiolitis, expiratory CT scan may be the only imaging technique that shows abnormalities in the early phase of disease. In order to obtain a good quality study, we should explain the procedure to the patient, use precise instructions and do some practice before image acquisition. Here we describe strategies to optimize the techni-que and propose an algorithm that help in interpretation of imaging findings in patients with obstructive airway disease.

CT findings of pulmonary cysts.

Pulmonary cysts are thin-walled radiolucent lesions that may appear in a variety of uncommon disorders known as diffuse cystic lung diseases (DCLD) that essentially includes lymphangioleiomyomatosis (LAM), Langerhans cell histiocytosis (LCH), lymphocytic interstitial pneumonia (LIP), Pneumocystis jiroveci pneumonia (PJP), and Birt-Hogg-Dubé syndrome (BHDS). Moreover, they have been reported in several cases of coronavirus disease 2019 (COVID-19). The purpose of this review is to provide a practical approach for evaluating lung cysts when encountered on CT. We describe the imaging findings of DLCD emphasising their differences in terms of shape and distribution of the cysts, as well as their association with other findings such as nodules or ground-glass opacities, which may help in making a confident diagnosis. We also discuss the link between pulmonary cysts and COVID-19.

[Liquefactive necrosis of the mitral ring]. / Necrosis licuefactiva del anillo mitral.

Liquefactive necrosis of the mitral ring is a rare type of periannular calcification that has a characteristic appearance. It is usually discovered incidentally during echocardiography. On CT, it typically appears as a hypointense or hyperintense semilunar mass with margins of greater density that is situated in the area behind the annulus. The routine use of MDCT has led to increasing detection of this entity, and it is important for radiologists to be familiar with these findings to avoid diagnostic errors. We present three cases of liquefactive necrosis of the mitral ring, one of which was confirmed at surgery. We discuss the imaging characteristics and differential diagnosis of this entity.