A common problem with any x-ray manufacturer offering APR techniques, or any printed technique guide or chart is that they are really only a starting point and must be modified for any specific location. 

When a manufacturer writes the software for an APR program, they do not know the brand of film processor, the brand of chemistry, the temperature of the developer, the length of time the film is in the developer (processors can be 90 sec, 120 sec, 180 sec etc), nor do they know the grid ratio.  Or course the brand of cassette screens and film (referred to as screen film combination and generally rated at 400, 300, 200 or 100 speed) can also make a huge difference too.  In addition, each x-ray tube has different emission characteristics.  So the amount of radiation varies from one tube to another, even though the filament current may be the same. 

All of these issues are variables that can differ from location to location.  One of the biggest variables is the time since the processor chemistry was changed.  In a busy facility running lots of films, the developer will be more replenished over time whereas in a more quiet x-ray environment, the developer may be more "tired" after only a week.  The concentration alone can contribute to a 25% density change.  As the month goes on, your films will get lighter and lighten until the chemistry is changed, at which point they will suddenly become very dark again (with the same technique).   

It is recommended that before any technique changes are performed, the chemistry be changed so you are at a known starting point.  You can now adjust a view to the doctor's desire, note the parameters changed, go into the edit program (see attached) and make the changes and save them so they will become the new default techniques the next time you do the same view.  You will still have to deal with the chemistry replenishment issue and understand that as you approach the suggested 30 day time to change the chemistry in the processor, you will need to boost technique to compensate by possibly 10% to 20%. 

You can always override the program APR settings, but unless you go into the edit program and save them they will not come up the next time.  Most digital algorithms will work with most APR programs, but watch your S numbers to ensure you are not over radiating your patients.  Low S numbers mean higher dose.

Last Updated 05/23/08

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