Final answer:
For a patient with widened mediastinum after injury, initial imaging typically includes a chest X-ray followed by a CT scan for detailed assessment. MRI can provide more detailed soft tissue images but is less common in emergency settings, while ultrasound is not typically used for the mediastinum itself.
Step-by-step explanation:
When a patient presents with a widened mediastinum after an injury, certain medical imaging studies are utilized to assess the extent and nature of the condition. A chest X-ray is often the initial study because it can quickly provide an overview of the thoracic structures, including the mediastinum, and it can show changes in width or abnormalities. If the chest X-ray suggests an abnormality, a CT scan (Computed Tomography) is usually the next step; it offers detailed cross-sectional views of the mediastinum, helping to localize the injury and identify any associated complications, such as hemorrhage, vascular injury, or other pathology. An MRI (Magnetic Resonance Imaging) may be used for more detailed images of the soft tissue structures within the mediastinum, but it is less commonly used acutely due to longer scanning times and less availability in emergency settings. Finally, ultrasound is less commonly used for imaging the mediastinum, as it is limited by air in the lungs and the bones of the chest wall, although it might be employed to assess related areas like the heart with an echocardiogram.