Path for ratings images

I saw that the latest fix was to add a leading slash in front of $module_dir. That only seems to work if drupal is the DocumentRoot. Doesn't it need to have the base_path() inserted in place of the leading slash ?
<img src=\"".base_path()."$module_dir/images/rating$node->rating.gif\" .......
<img src=\"".base_path()."$module_dir/images/rating$selected_book->rating.gif\" ......