Display images that are not in the content

The function below returns all the images attached to the post, however, if I delete the image inserted into the content, it still returns in the function, because the media is still as attached to the post.

So, how do I really bring only the images inserted in the content of the post?

<?php  $  args = array(         'post_type'   => 'attachment',         'posts_per_page' => -1,         'post_mime_type' => 'image',         'post_parent' => $  post->ID,     );      $  attachments = get_posts( $  args );      if ( $  attachments ) {          foreach ( $  attachments as $  attachment ) {              echo wp_get_attachment_image( $  attachment->ID, false );             echo '<hr>';             echo '<br>';          }     } ?>