$q = new Doctrine_Query();
      $q->from('UserImagefile uif');
      $q->innerJoin('uif.Imagefile if');
      $q->where('if.md5hash = ? AND uif.user_id = ?', array($image_id, $user_id));
      $user_imagefile = $q->execute()->getFirst();
      if (empty($user_imagefile)) {
        throw new XZ2Exception(__METHOD__.' - No image found with id: '.$image_id, XZ2Exception::NOT_FOUND);
      }

      $user_imagefile->Imagefile->delete();