imagecache images in themes directory

hi there,

Is it possible to use imagecache on images that reside outside the "files" directory?

theme('imagecache', 'large', drupal_get_path('theme', 'mytheme') . '/images/myimage.gif', NULL, '', '', array()) 

I just can't get this to work. (imagecache works fine with files under the 'files' dir).

Thanks