Chest x-ray is the initial imaging technique used to diagnose TBI.[9] The film may not have any signs in an otherwise asymptomatic patient.[13] Indications of TBI seen on radiographs include deformity in the trachea or a defect in the tracheal wall.[9] Radiography may also show cervical emphysema, air in the tissues of the neck.[2] X-rays may also show accompanying injuries and signs such as fractures and subcutaneous emphysema.[2] If subcutaneous emphysema occurs and the hyoid bone appears in an X-ray to be sitting unusually high in the throat, it may be an indication that the trachea has been severed.[4] TBI is also suspected if an endotracheal tube appears in an X-ray to be out of place, or if its cuff appears to be more full than normal or to protrude through a tear in the airway.[9] If a bronchus is torn all the way around, the lung may collapse outward toward the chest wall (rather than inward, as it usually does in pneumothorax) because it loses the attachment to the bronchus which normally holds it toward the center.[6] In a person lying face-up, the lung collapses toward the diaphragm and the back.[10] This sign, described in 1969, is called fallen lung sign and is pathognomonic of TBI (that is, it is diagnostic for TBI because it does not occur in other conditions); however it occurs only rarely.[6] In as many as one in five cases, people with blunt trauma and TBI have no signs of the injury on chest X-ray.[10] CT scanning detects over 90% of TBI resulting from blunt trauma,[3] but neither X-ray nor CT are a replacement for bronchoscopy.[6]