I have worked with several mothers who have been given "directions from the
manufacturer's label" for recommended length of time away from nursing after
scans.  I have found the best solution is to personally call the TECH who
does the procedure and ask which medium will be used for this particular
test, then LOOK IT UP in all my references.  You will find wonderful
resources in Hale, Lawrence and the Riordan/Auerbach books.  When a new
medium comes out, I have called the Lawrence Center in Rochester.  The most
common ones I have seen being used lately are Technecium 99 and Magnavist.  I
had one mother call me in tears because her dr. told her she would NEVER be
able to breastfeed again.  After determining that they would be using tch 99,
I provided the book references to the physician (and the department
performing the procedure) and the phone number to the Lawrence Center.  He
was most appreciative and has referred other mothers to me as a result.
Good luck, and don't be afraid to call around until you get the answers you
need to help the mother make an INFORMED decision.
Liz Flight, RN, CLE, IBCLC
Jacksonville, Florida