[Zope] Content-type for a method or script

I need to render an image with some logic from a request in an external (non-zope page) example request from html: <img src="http://zope/images/header.gif?UID=sdflkj"> DTML_Method "header.gif" <dtml-call "RESPONSE.setHeader('Content-Type', 'image/gif')"> <dtml-var mytestgif> my ID=<dtml-var UID> mytestgif is an 'Image' in zope. It renders fine when I test the URL http://zope/images/header.gif?UID=sdflkj But, the Method does not render when called from within <img src> in another page!!! I got the same result with a script. Please point me in the right direction... Thanks Trevor