Institutional Paranoia

I have to share this "adventure" with you.
As part of a series of diagnostic tests I'm undergoing, (the joys of getting older), I am undergoing a MIBI stress test. The first stage involves an injection of some radioactive isotopes as a tracer into my blood stream and a few images being taken shortly there after. Step 2 will involve an exercise bike and other torture devices as they try to establish if I have some blocked arteries.
As the nurse was reviewing my history and such in advance of the first step, she asked if I was planning on traveling into the USA any time soon. I told her that I planned to go there immediately after we were done. Some key parts for the next kit had finally arrived at my PO box in Michigan and I needed to get the pilot model built.
She said "Then you'll be needing this." She handed over a card that described what the procedure was and the dosage and what the actual materials were that were being injected. She informed me that I should expect to be questioned at the border as they maintained Geiger counters at the crossing points and I might set them off.
In my mind I had a hard time believing that the relatively small amount of nuclear material that was in my body would set of an alarm. So away I went.
Arriving at the border at noon on a Friday, the volume was pretty much what I was expecting. But the traffic was moving through the check points fairly well. I was one car away from advancing to primary screening when suddenly everything stopped and 8 CBP personnel were walking around the driveways with little handheld devices. I knew what was up.
I rolled down the windows and waved, calling out, "I think you're looking for me!" The first agent came to the window and asked, "Did you have a medical procedure today, sir?" I told him I had and handed over the card I had been given.
From there I was quickly through primary and into secondary inspection and instructed to drive the van through some form of detector, and they then had me exit the van and move away. I was then scanned by a more sophisticated Geiger counter while the agents were busy filling in paperwork. The one agent with the counter asked me when I had had the procedure done. I told him "Just this morning." To which he responded "That would explain why you're so hot!" I smiled and said" It's been along time since anyone has called me that." He didn't smile back. ( no sense of humour these guys.)
Any way they were all very polite and I was on my way fairly quickly. But I am rather astonished at how sensitive the radiation equipment is at the border. Remember that the initial reading was taken while I was inside a steel box and that medical isotopes are fairly low level items.
Are they really that afraid of a nuclear device being smuggled into the USA? A certain amount of paranoia is a healthy thing, I've been told, but this is a little much I think.
Oh and the really weird part, coming home an hour later, no alarms were set of returning to Canada.
You may draw your own conclusions.