From the article:

"The detectors can be set off by low levels, such as by patients undergoing chemotherapy or someone who recently had an X-ray. Potassium in bananas could also set it off. "

This strikes me as an utterly absurd statement. The chemotherapy statement is a source of great confusion - that somehow irradiating a tumor (or fruits, for example) somehow makes them radioactive. While there may be highly-specialized chemotherapy agents that are radioactive (such as specially prepared antibodies that bind specifically to tumor cells so as to target the radioactivity to the malignant cells and selectively kill them), most chemo agents work in a totally different manner.

The naturally-occurring level of the radioactive isotope of potassium must be incredibly low and thus difficult to detect. Perhaps someone from the "apple" industry wrote the article.

OTOH, RobertS975's comment raises a valid concern.