以下是一种方法:
\documentclass{article}
\usepackage{tikz}
\def\MD{%
\begin{tikzpicture}
\draw[text=white,font=\Large\sffamily,draw=none,fill={rgb:red,54;green,58;blue,142}] (0,0) circle[radius=.8cm] node {MD};
\end{tikzpicture}
}
\begin{document}
Test: \MD
\end{document}