Custom Fields outside of loop

Hi

I’m trying to query thumbnail photos put into custom fields and display them outside of the loop. I have a “Most Commented” section and I’d like to bring in each post’s respective thumbnail photo, which is housed in a custom field called “small_photo”. You can see what I’m attempting to do if you click on the “Popular” tab at right here:

https://graphpaperpress.com/dev/

Here is the existing code, which wrongly pulls in the “small_photo” of the latest post:

<!-- POPULAR (MOST COMMENTED POSTS) -->

<div class="t2">
<ul class="popular">

<?php $result = $wpdb->get_results("SELECT comment_count,ID,post_title FROM $wpdb->posts ORDER BY comment_count DESC LIMIT 0 , 3");
foreach ($result as $topten) {
$postid = $topten->ID;
$title = $topten->post_title;
$commentcount = $topten->comment_count;
if ($commentcount != 0) { ?>

<li class="clear">

<h6><a href="<?php echo get_permalink($postid); ?>" title="<?php echo $title ?>"><?php echo $title ?></a></h6>

<a href="<?php echo get_permalink($postid); ?>" title="<?php echo $title ?>">
<img src="<?php $key="small_photo"; echo get_post_meta($post->ID, $key, true); ?>" alt="" class="photo_align_left" /></a>

<ul class="small">
<li><a href="<?php echo get_permalink($postid); ?>#respond" title="<?php echo $title ?>"><?php echo $commentcount ?> comments</a></li>
<li><a href="<?php echo get_permalink($postid); ?>" title="<?php echo $title ?>">Read &rarr;</a></li>
</ul>

</li>
<?php } } ?>
</ul>
</div>