Answer to Question #10458 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Equipment

The following question was answered by an expert in the appropriate field:

What would be a good detector to buy for measuring x-ray machine radiation around a cabinet x-ray system used for checking food products?
For cabinet x-ray systems, typically used for checking items for hidden foreign objects, a standard Geiger counter with a thin-end window would be used to detect if any radiation leaks were present. The Food and Drug Administration (FDA) regulates cabinet x-ray systems and their emission limit is less than 5 microsieverts (uSv) in one hour at any point five centimeters outside the external surface. Geiger counters are great for detection of leaks, however to measure any exposures accurately, I would recommend an ion chamber survey meter. Geiger counters typically will overrespond to the low-energy x rays used in these devices and give an erroneous measurement, so to measure the exposure levels accurately, an ion chamber would be used. Unfortunately, ion chambers are terrible detection devices, so both devices would be necessary to document compliance with the FDA regulations.

You should also be aware that cabinet x rays are equipped with safety interlocks to prevent them from being operated with the shielding open. A comprehensive safety inspection would also include interlock checks to confirm that they are operating properly.

You might want to take a look at the FDA website and regulations that cover these types of systems. Additionally, your state regulations may require periodic safety inspections of cabinet x-ray systems by a radiation safety professional.

Mike Bohan
Radiation Safety Officer
Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 29 October 2012. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.