New columns.. or a whole new table?

Hi,

I wrote a hack for my forums that allows users to upload images and documents and add descriptions to them.

I'd like to make the descriptions searchable, and use the same method that the forums search uses. I would have to index the descriptions in the same manner as vBulletin indexes each post.
I'd like to use the same word table, as not to duplicate that data.

But here is where I have my question: What would you suggest I do:
a) Add columns (docid,doctitle) to the searchindex table, to account for the documentid where that word occurs
b) Add a whole new table (wordid,documentid,intitle,etc), and not mess with the vBulletin tables

Thanks for your input.

Brandon