Chest radiograph

Chest radiography has been traditionally used to evaluate the chest, including lung parenchyma, airways, and mediastinum. Despite the wide use of computed tomography imaging, chest radiography still plays a fundamental role in the detection and characterisation of mediastinal lesions through the use of mediastinal lines, stripes, and interfaces. Lines and stripes are formed by air outlining thin or thick intervening tissue on both sides, respectively. Interfaces are formed when structures of different densities contact with one another, such as in the azygoesophageal recess. The recognition and understanding of the anatomic basis of these mediastinal lines, stripes, and interfaces along with their normal and abnormal appearances allow radiologists to develop an appropriate differential diagnosis of mediastinal lesions before obtaining additional information by using chest computed tomography or magnetic resonance imaging.

Chest imaging remains one of the most complicated subspecialties of diagnostic radiology. The fundamentals in the interpretation of chest imaging are the knowledge of the normal anatomy as well as the radiographic signs. Anatomy of the respiratory system and its variants in the different imaging techniques will be reviewed, including chest radiography, CT and MRI. Monitoring and support devices such as different types of tubes and lines will be shown along with their correct position in the chest. Chest radiography signs are helpful in establishing a particular diagnosis of chest diseases. Therefore, their recognition and understanding is of particular interest for general and subspecialised thoracic radiologists. During the presentation, many radiographic signs will be discussed, including silhouette sign, air bronchogram, air crescent sign, cervicothoracic sign, gloved finger sign, golden S sign, deep sulcus sign, coeur en sabot sign, doughnut sign, double density sign, hilum convergence sign, hilum overlay sign.

The normal appearance of the diaphragm is usually similar on both sides. The diaphragm may be elevated on either side due to abdominal tumours, paresis of the phrenic nerve, traumatic rupture, or subpulmonic pleura effusion. The pleura may be thickened due to effusion, fibrosis with or without calcifications or due to malignancy. The chest wall has a varying normal appearance according to the shape of the rib cage and sternum. The mediastinum is a complex anatomic area which is affected by changes in vascular system and lymphadenopathy. In addition, various diseases like infections and tumours can be seen in the mediastinum. The postoperative chest radiograph is sometimes challenging to read because it usually is done in a supine position and only a front image is performed. It is important to recognise “do-not-miss” pathology such as pericardial fluid, tensions pneumothorax, or malpositioned tube and central lines.

Missing lesions on chest radiographs are frequent and the largest source of medico-legal issues. In this course, we report reasons for missing lesions, we distinguish perception and cognitive errors, and we comment on missing nodules, consolidations and infiltrative lung diseases. We provide tips to reduce our error rate, and in particular, we comment on the importance of learning and applying key signs for optimising the detection of abnormalities on both the frontal and the lateral views of the chest.

The presentation will provide a reading guide for the frontal and lateral chest radiograph. The most useful signs in chest radiology will be introduced, using side-by-side plain film and CT imaging to help understand the imaging features. Although the clinical value of the chest X-ray remains undiminished, errors of interpretation of the chest X-ray remain one of the most frequent causes of malpractice issues. The skills required for accurate interpretation of the chest radiograph will be explored. The objective is to help you improve your performance in plain film interpretation of the chest.

Many acute or chronic diseases of the lung may manifest at imaging with the appearance of an alveolar, interstitial or nodular syndrome. All of these imaging syndromes are well known to thoracic radiologists and can be detected at chest radiography. Especially when interpreted in the correct clinical setting, alveolar, interstitial or nodular opacities can provide hints to the diagnosis. In this presentation, the typical imaging signs that allow to make a diagnosis of an alveolar or interstitial disease or suspect the presence of pulmonary nodules will be reviewed by using anatomic and imaging correlation between chest radiograph and CT.

Lobar collapse or closure of a pulmonary lobe is associated with a loss of volume and results in reduced or absent gas exchange, a condition where the alveoli are deflated down to little or no volume. This presentation aims to review the radiographic and CT signs of lobar collapse, or loss of volume, and associated abnormalities when for example the cause of the collapse is a bronchial obstruction of a mass. Differentiation of lobar collapse and consolidation will be discussed. Distinct entities will be imaged such as aerated lobar collapse and chronic lobar collapse without mass-like consolidation.

Chest radiographs are particularly useful to diagnose pneumothorax, albeit smaller ones may be missed on radiographs. Pneumothorax is commonly seen as an area of hyperlucency with lack of vessels in the apical and the lateral regions on the photograph performed standing or sitting. Pneumothorax in the supine position is best seen as the deep sulcus sign as the air moves anteromedially and subpulmonic. Pneumothorax can be spontaneous (either primary or secondary) or iatrogenic. It is important to recognise the “do-not-miss” state of tension pneumothorax, which can be fatal if left untreated. A partial pneumothorax is seen when part of the lung is still adherent to the chest wall. It is, however, important to differentiate it from bullous lung disease, which sometimes may be difficult on radiographs, and may require a CT for a definite diagnosis.