How to create menu with elements only one of which can be checked

What is the shortest way to create menu with elements only one of which can be checked at same time? So if user click second element, first check becomes unchecked. Actually would prefer small circles instead of checks.

   <Menu>
        <MenuItem Header="File">
            <MenuItem Header="Numer">
                <MenuItem Header="1"
                          IsCheckable="True" />
                <MenuItem Header="2"
                          IsCheckable="True" />
            </MenuItem>
        </MenuItem>
    </Menu>