UNKNOWN
I am reasonably familiar with Iskan and Helmer's book, because I reviewed it for one of the journals a few years ago, there are a number of different articles which state a number of different opinions in that book, as you would appreciate once you peruse it, and there is quite a lot of repetition as well, which sometimes is a good thing in a book like that.  But I have to say at the end of the day, the technique that we use, we're quite happy with and we're fairly rigorous in what we carry out, and because - we don't use radiography, because radiography, I believe is not relevant to these particular images, but if you use radiography, then there are different issues involved.
	On would need to have a much fuller discussion on that area if that is what you point to, but I would need to have the book in front of me as well to refer to it.