My daughter had these test done also.  She went to Children’s of Dallas for them.  I was allowed to stay for both tests.  The ultrasound is no big deal, but the other test is pretty uncomfortable for them.  I hated it, but it had to be done.  The staff was great with my daughter and tried to make the procedure as comfortable as possible.  I would want to be there.  I would ask the reasoning behind you not being there. 

Carrie