See attached my example:
1) Supine chest radiograph with skin breach marked on the upper left side of the chest (the right side on your screen). That diffuse opacity of the left lung is a haemothorax which doesn't have an obvious fluid level because the image was taken supine.
2) Erect view of the same case. Note how the bullet now sits more inferiorly. This indicates it is in a tissue plane where it has some movement (both because of gravity and because of freedom to move in that tissue). You could argue there is a fluid level at the left lung base (right side of your screen) but that's diaphragm area also, so it is hard to visualise. This image is taken before the insertion of the chest drain. Note the subcutaneous emphysema and lung contusion.
3) Lateral view, very important to localise where this projectile is. Here we see it is posterior. Trajectory is left postero-lateral chest moving through the left lung on a posterior course to a position outside of the thoracic cavity behind the right lung. That thick coiled tube is a chest drain.
You can read more about skin breach markers here:
https://www.linkedin.com/today/posts...tolli-b6500522