If you are entering the United States following a Nuclear Medicine procedure you will be detected by the radiation detectors located at the border crossing. For most procedures, you will be detectable for up to 3 days following your test and with some procedures (Iodine-131 Whole Body, Gallium Scan, Octreoscan, etc.) you may be detectable for a few months. If you plan on or think you might be entering the United States following your procedure please let the technologist know and they can provide you with a letter confirming you underwent a procedure that involved the injection of radioactive material.