Answer:
Positron emission tomography. Positron emission tomography (PET) is an imaging technique that uses radioactive substances to visualize and measure metabolic processes in the body.
Horizontal forehead wrinkles are caused by contraction of the frontalis muscles. The frontalis muscles are two large fanlike muscles that extend from the eyebrow region to the top of the forehead. I think this is the answer
Drink lots of water, take breaks in the shade
Their is going to be 4 sig figs