Categories, sub-categories with images

Hello.

Using this code for listing categories with images.

<?php
$image_path = get_bloginfo('stylesheet_directory');
$cats = get_categories();
$count=1;
foreach ((array)$cats as $cat) {
	$catdesc = attribute_escape(strip_tags($cat->category_description));
	$image = $cat->category_nicename .'.jpg';
		$cat_img = '<div class="category-image" id="cat-image-'.$count.'"'.'><a href="' . get_category_link($cat) . '" title="'. $catdesc .'"><img class="image-for-category" src="' . $image_path . '/images/' . $image . '" alt="' . $cat->cat_name . '" /></a></div>'."\n\n";
	echo  $cat_img ;
	$count++;
}
?>

But I have sub-categories and I dont want to add images for sub-categories.

How can i do it?

I will create a theme like Directory Press.