Bullets
There are bullets, which are black hole artifacts over L3 and L4. Because the internal artifacts overly bone, they are removed from analysis.

There are bullets overlying L3 and L4. The bullets are made of lead and in the dual-energy mode they appear black and are called black hole artifacts. If they are viewed in single energy, they would be white.
Sarah L Morgan, MD, RD, CCD, The University of Alabama at Birmingham
• Morgan, S.L., et al., Black hole artifacts-a new potential pitfall for DXA accuracy? J Clin Densitom, 2008. 11(2): p. 266-75.
• Morgan, S.L., et al., More on the black hole: tantalum, stainless steel, titanium, and lead J Clin Densitom, 2007. 10(2): p. S202-S203
• Morgan, S.L., et al., Effect of very dense artifacts on Hologic and General Electric bone densitometry results. . Arch Osteoporos 2020. 15(1): p. 77.