How to display CCK field in head title

Hi,
I have created CCK fields and want to use the value of one CCK field to display/override the default head title.

I have used following method but output is blank.

function mytheme_preprocess_page(&$vars) {
$meta_description = $node->field_meta_description[0]['view'];
if (!empty($meta_description)) {
$vars['head_title'] = $meta_description;
}
}

Regards,
Anup S

I am newbie in this drupal. Can somebody help me to fix this problem.