Compare an original video with a transferred video?
There are quite a few programs that do so-called "full reference" measurement, i.e. comparing an original against a degraded signal:


http://www.acceptv.com/en/products_vqa.php
http://compression.ru/video/quality_measure/index_en.html (commercial)
http://www.its.bldrdoc.gov/resources/video-quality-research/guides-and-tutorials/description-of-vqm-tools.aspx (free to use, gives results on a 0-1 scale)
http://mmspg.epfl.ch/vqmt (free to use, calculates various metrics)


These are all outputting some value that you can use to objectively compare different systems. 

However, keep in mind that the results you get from such a software may not correspond exactly to what humans would rate. These metrics have been trained on natural images and movie sequences and the results may not be valid for medical purposes.

I would suggest you try VQM (it is standardized by the ITU) and image metrics like SSIM. They perform very good, in principle. Then check whether the results are what you would expect when looking at the videos yourself. You could do a small test with a few experts and let them rate a few sequences, then compare the results with the objective values you obtained from the software.