Converting PowerPoint Notes Page to PDF - Is it possible to carry over the slide programming

I have to convert the Notes pages of a training presentation built in PowerPoint 2007 to a 508-compliant PDF. I've successfully produced the PDF with a relatively clean accessibility check, with the exeption of the slide thumbnails. The thumbnails, which were all programmed with alt text for all images on the PowerPoint slides, register "no alt text" errors. The slide content reads perfectly when I use the Read Out Loud function (as it's tagged as text), except that none of the image alt text that was programmed into all the PowerPoint images carries over to the PDF.
 
I know that if I had converted the slides to PDF from Normal view, I would have the text and images register appropriately, along with any alt text programmed into the presentation; however, I also realize that the image used for the slide thumbnail is actually a projection of the slide content and may vary well only register as an image. I'm still holding out hope that there may still be some connection between the Normal and Notes views that I can exploit to allow the slides to function appropriately in the PDF while still using the Notes layout. I understand that I may need to resort to manually tagging each of these slide thumbnails, but is there any way to convert the PowerPoint Notes pages so that the thumbnails behave as regular slides do when converted to PDF from Normal view?
 
Any advice would be greatly appreciated.