<?php
$img_id = get_post_thumbnail_id($post->ID); // This gets just the ID of the img
$image = wp_get_attachment_image_src($img_id, $optional_size); // Get URL of the image, and size can be set here too (same as with get_the_post_thumbnail, I think)
$alt_text = get_post_meta($img_id , '_wp_attachment_image_alt', true);