depends how good you need it - if it's just your personal use then you could get a way with scanning the drawing into a program like Coral or Adobe photoshop and then rendering it that way. If you want a vector version and plan to go to print with it or put it on the back of your rib etc (and one you can enlarge to any size), then Adobe Illustrator would be the tool of choice. But you will have to learn all these programs, it's not quite as easy as buying it and then drawing on screen - you'll need to learn the tools, what they do and how to work them right.
here's a photoshopped rib i did from a line drawing:
if it's just an effect you want - you can buy Photoshop Elements which is probably a quarter of the price of Photoshop, you should be able to turn the picture into a line drawing in that - other than that, and to get a proper job done the only way is to pay someone like me
post the pic up if you can...