Ummm...sort of. You can mess around on the Master slide and apply a border to the main panel where you adjust all the Master text styles. This will put a border around any of the main content (not the title of each slide) that exists on the slides.
(You can get to the master slide by going up to "View" and going to "Master." Be sure the "Slide Miniature" is shown so you can see exactly how it will affect the slides in question.)
This may or may not be exactly what you want. If you only have the xray on the slide, this will work perfectly. However, if you have other text (other than just the title, perhaps), there will be the same border around that, too.
Hope that's helped.