/ build Tooltip text
      $tooltip = '<h3>' . $variables['element']['#object']->title . '</h3>';
      $summary_field = $variables['element']['#object']->field_summary;
      if ($summary = $summary_field[LANGUAGE_NONE][0]['safe_value']) {
        $tooltip .= '<p>' . $summary . '</p>';
      }

      foreach($variables['items'] as $key => $item) {
        $variables['items'][ $key ]['#prefix'] = '<span class="jquery-ui-tooltip" title = "' . $tooltip . '">';
        $variables['items'][ $key ]['#suffix'] = '<span>';