How to link Similar-but-distinct Models of Medical Imaging Data?
Since you said that there are always 2 types of data I would do it like this

This might use the wrong terms since I don't know what exactly is available, but I think you will get the idea.

image (the data that is common to both scanes/images)
---------------------------
    image_id
    date


coordinator (the one that is inserted by hand)
---------------------
    image_id (PrimaryKey and ForeignKey)
    comment
    description
    order
    [...]

metadata (that you get programmatically)
----------------------
   image_id (PrimaryKey and ForeignKey)
   {whatever data that is}


This way, you have both images connected but have the freedom to model the details differently.

Additionally, you could move the metadata into a seperate table if the data is similar. This might be useful for later comparisson/collection/...

metadata (that you get programmatically)
----------------------
    image_id (PrimaryKey and ForeignKey)
    metadata_id


metadata_description
-------------------------
    metadata_id
    description
    name
    {whatever the metadata is}