Absolutely nothing to worry about. You don't have to interrupt breastfeeding even for one second. See attached. Take with you and if they tell you that you have to stop, hand them a copy of the statement by the American College of Radiologists.
For general breastfeeding information, see www.drjacknewman.com
See also the attached chapter on drugs and breastfeeding from my book, Dr. Jack Newman's Guide to Breastfeeding (HarperCollins, 2nd revision 2005) as it's called in Canada, or The Ultimate Breastfeeding Book of Answers as it's called in the US (now out in a new edition, as of November 2006).