Pagination with custom queries possible?

I’m using a custom query in order to show only posts with a certain custom field value. See below:

<?php $querystr = "
    SELECT wposts.*
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
    WHERE wposts.ID = wpostmeta.post_id
    AND wpostmeta.meta_key = 'imagetype'
    AND wpostmeta.meta_value = 'photoshop'
    AND wposts.post_status = 'publish'
    AND wposts.post_type = 'post'
    ORDER BY wposts.post_date DESC
 ";

 $pageposts = $wpdb->get_results($querystr, OBJECT);

if ($pageposts):
  foreach ($pageposts as $post):
    setup_postdata($post);
?>

I want to add pagination to it since this query will show all entries (like 400+ and that’s a bit too much to load). Is there a way to combine above code with posts_per_page option like below?

<?php query_posts('posts_per_page=48' . '&orderby=modified&paged=' . get_query_var('paged')); ?>

Maybe possible with other query? I also tried to set the maximum post ammount, but the custom query overrides it and there is no pagination what so ever.