Medical imaging is often perceived to designate the set of techniques that noninvasively produce images of the internal aspect of the body. In this restricted sense, medical imaging can be seen as the solution of mathematical inverse problems. This means that cause (the properties of living tissue) is inferred from effect (the observed signal).
Definition. Et al. is a Latin abbreviation that means 'and others'. It's used in place of names for the purpose of saving time and space when providing in-text citations.
English - US. If pushed, I would put the 's with Johann: Johann's et al. findings. I would not attach it to et al., because al. is the abbreviation of a Latin word, and Latin doesn't form the possessive by 's. I would far prefer to get around the question by writing: the findings of Jahann et al. Dec 1, 2009.