Physics of Radiology isn't as complete a text as Martin's, it seems more like a handbook than a physics text, but it is definitely useful and is full of examples that I can't find in other books. It's a little difficult to read straight through because of the visual format (it looks like it was written on a typewriter), but the examples are great references. I would have liked it if the authors used units more often, so that I could more easily adapt the examples but in all, it was a good investment.