We get asked many questions regarding safe room design and safe operating procedures.  The following comments are from Roy Duncan, owner of Les Wilkins.  Roy is a Qualified Shielding Designer and performs health physics shielding calculations for the design of barrier walls and primary walls.  He is also considered a shielding expert in room shielding and x-ray procedures  involving scatter and leakage radiation.  Roy holds a degree in electrical engineering and consults extensively with the State Health Physicists as well as private industry.

"Although I am wearing gloves, I can see the outline of my fingers outside the collimated image when radiographing animals while holding them.   Doesn't this mean my collimator or x-ray machine is putting out too much scatter radiation?"

Probably not.  This is what we would expect as scatter radiation comes from the patient, not the collimator.  Technically there is some "off focus" radiation that does come from the collimator, but it is fixed and not a variable like true "scatter radiation".  There is also "leakage radiation" which is also a fixed amount, but again there is little you can do about it but these components are why you are required to wear apron, gloves, thyroid collars and glasses when working at the table during procedures.

So scatter radiation comes from your patient and you can expect to see its effects outside of your collimated field.  If splitting a cassette with 2 views, always use a lead rubber divider to eliminate scatter effects on the other view.  

"I don't wear gloves at the table because I am afraid that the lead will hold in any scatter radiation that I receive.  I think it is safer to not wear any gloves at all."

A technologist enquired about x-ray gloves holding in radiation rather than blocking it.  I have never heard of this issue nor can I see how it is physically possible. WEAR YOUR PROTECTIVE APPAREL AT ALL TIMES.

We are also asked to sell "slit gloves", "slit mittens" or devices that cover only the tops of hands.  We do not like these as they give a false sense of security to the wearer.  They do provide some Primary Beam protection, but they do not provide any scatter protection as scatter comes from the bones of the patient.  If your fingers are touching the patient then your fingers are unprotected from direct scatter which is not acceptable by any State (or common sense) standards.

It is also true that most new collimators have better shielding than older collimators.  One particular model has been sold in the veterinary industry for many years is the Duocon I.  Made by Machlett Labs in the 70s and 80s, they are no longer being manufactured today.  These collimators are quite "leaky" by modern standards however they do meet all state requirements for veterinary use.  A nice upgrade for older equipment would be to buy a new replacement collimator with a 150 watt halogen light bulb.  Not only would your field be improved, but off focus radiation would be reduced. 

Leakage radiation comes from the tube housing and is almost nil in a modern rotating anode tube design.  Unless you are very paranoid, forget this issue.  EXCEPTION...Note that some veterinary techs will position their head within a couple of inches of the x-ray tube while standing in front of the table.  This does raise the issue of eye protection and thyroid protection.  We would like to see all techs wear thyroid collars and lead eye glasses in order to reduce the effects of scatter and in this case leakage radiation.

Remember that air is an excellent barrier and radiation intensity falls with the square of the distance.  (The effects at 4' are 1/4 the effects at 2').  The further you are away from radiation the better.   Wear your radiation badges and store them away from the x-ray machine.

LAST UPDATED 5/22/06

Last Updated 05/23/08

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