\documentclass[12pt]{report}
\usepackage{graphicx}% Include figure files
\usepackage{amsfonts}

\begin{document}
\thispagestyle{empty}
\begin{center}
\begin{picture}(250,150)
  \includegraphics[scale=0.7]{TPS_b.eps}
  \put(-45,44){\Large $\Sigma$}
  \end{picture}
\end{center}
\end{document}
