500
The search patterns of a cxr go by this mneumonic
What is ABCDEF
Airway(trachea, bronchi)
Bony thorax (ribs, spine, scapula, clavicles)
Cardiac borders (size, clarity of borders)
Diaphragm (smooth, rounded, bilateral, elevated, costophrenic angles)
Everything else (soft tissue, interstitial edema)
Fields (lung fields....good expansion, clear, dark)