Widened upper mediastinum, with apical capping. Aortic knuckle outline very indistinct as blood obscuring the fat plane.
Now it's time to go back and look at the original film again:
Yes that's right - the mediastinum not widened but the calcification of the aortic knuckle can be seen within a soft tissue density, which means that a dissection has already started. There is no apical capping.
A powerful instrument the retrospectoscope.