[Spambayes] Images of commercial text with decoy text are mushing my index

[Jamie and Kim Murdock]

I am being assaulted by a new sort of spam where the commercial message is
contained in an image, and the text of the message is just there as a
decoy - it is excerpts of books, articles, etc.  Clicking spam on a few
dozen of these has made my index confused, and now not only are these
continuing to get through, but other obvious spam is getting misclassified.
See screenshot here http://members.cox.net/jmurdock1/spamExample.gif

How can Spambayes or anything else combat this?  Grrr

Jamie