the_post_thumbnail() issue with image ‘alt’ attribute

Hi,

I really want to know, is there any way to use alt attribute with the_post_thumbnail() function. for example I use following code to show featured post gallery in front page in my blog http://www.worthytips.com/ :

<div id=”featured” class=”clearfix”>
<?php $recent = new WP_Query(“cat=824&showposts=3”); while($recent->have_posts()) : $recent->the_post();?>

” title=”<?php the_title(); ?>” class=”featured_post”>
<div class=”featured_post_inner”>

<div class=”attach”><?php the_post_thumbnail(array(150, 150, true)); ?></div>

<h2><?php the_title(); ?></h2>
</div>

<?php endwhile;?>
</div>

Can anyone tell me how to put ‘alt’ image attribute on generated thumbnail.