How to get topic title in bb_plugins.php file?

I want to get topic title/name in the bb_plugins.php file to include in a meta code:

if($action=='vthread') $topicRSSMeta="<link rel=\"alternate\" type=\"application/rss+xml\" title=\"$GLOBALS['topic_title']\" href=\"{$main_url}/topic_rss.php?topic={$topic}\" />";

I tried all possibilities but I can't seem to get it.

Try $topicData[0].

Great! Thanks Paul :)