Doctor Terence Epstein was a Starfleet cybernetics expert in the 24th century and served as a professor at the medical school which Beverly Crusher attended.

Crusher attended some of his lectures while in school and called him one of the "leading minds" in his field.

In 2364, he was stationed at Starbase 74. The USS Enterprise-D visited there during this time, and Crusher hoped to consult him regarding her proposals for combining cybernetics with medical regeneration. (TNG: "11001001")

This character was only mentioned in dialogue.
A small scene in the script, which was cut from the episode, had Crusher speaking with Epstein in a starbase conference room. He was established as a young man of twenty-six years old. In his fifth paper on molecular biology, he defined the problem as conductivity. [1]