It is my understanding that the PST is a MS proprietary file, only readable by Outlook, and there isn't anything that can directly access it unless Outlook is runnning. Then SAV or SEP access it as a plugin to outlook.
So, unless Symantec corrects me, I don't think you CAN scan a PST file............ well, you could scan it, but it would be like an encrypted ZIP file with a password - SAV would not understand the contents.