How to display review image on review gird in adminhtml?

Question

I add a review_images in review_detail,and I can add images form product page. And now I want to display review images in All Reviews list in admin.

        public function getReviewImages($reviewId){
        $collection = Mage::getModel('review/review')
                        ->getCollection()
                        ->addFieldToFilter('main_table.review_id',$reviewId);
        $collection->getSelect()->columns('review_images','detail');                

        if($collection->getSize()>0){
            $review =  $collection->getFirstItem();
            if($review->getReviewImages()!=''){
                return $review->getReviewImages();
            }
        }

        return false;

    }

But how can I display review images on review list?