This is an interesting little lecture that draws attention to the long road between raw imaging input and the manipulation of the parameters on which interpretation is based and judgement calls are made.

Of particular interest is the amount of 'medical photoshopping' that has to be carried out before you can say anything meaningful about an image. Also, note the role of subtraction in defining the relativity of meaning, just like the constitution of subjectivity in the rest of life.

http://www.youtube.com/watch?v=iSSiN5OrRig