**4.1 Plain chest X-ray**

The diagnosis of pneumothorax is usually confirmed by imaging techniques such as PA chest radiograph, and the excess radiation dose should be avoided in this young patient population. The diagnostic hallmark is the displacement of the pleural line. The pneumothorax is most frequently seen at the lung apex, but lateral, subpulmonic, and medial collections of air can also be seen [33]. Chest X-ray is the first diagnostic evaluation imaging being used, but small-sized pneumothoraces or loculated pneumothoraces can be missed on chest X-ray. If a pneumothorax is suspected and is unrevealed on chest X-ray, a more specific diagnostic imaging like chest computed tomography (CT) is necessary [34].
