Echo a Variable."_string" (concatenated with a string)

Hi Guy's any idea on how to make this work?

<?php $themename_orig = get_bloginfo ( 'name' );
      $clean = toAscii($themename_orig);
      $shortname_opciones = $clean;
?>
body { 
background:url("<?php echo $shortname_opciones."开发者_StackOverflow_bg_img"; ?>") no-repeat scroll center top 

<?php echo $shortname_opciones."_color_bg"; ?>; 
}

#logo 
{ 
background: url("<?php echo $shortname_opciones."_logo"; ?>") 0 17px no-repeat; 
}

Basically my problem is that I need to echo a variable after concatenating it with a string, that variable does exist.

echo ${$shortname_opciones."_bg_img"};

background:url("<?php echo $shortname_opciones; ?>_bg_img")