EDIT: Whoops, I didn't notice they cut off part of the title. It's suppose to read "How can I remove the dirty white background of my scanned artwork without sacrificing the sketch?"
I have an old sketch made about 10 years ago. There isn't much shading but there are area's where the dirty paper from aging and wear really shows from my scanner. I scanned in top quality which shows the defects of the paper really well. How can I remove this so it looks like it's on a clean piece of paper? This is really important to me, I'll be submitting it for a competition. Any help would be greatly appreciated!