Sandy's EPD Comments

["John R. Laferriere 671-8316" <John.R.Laferriere@dupontpharma.com>]

Sandy- You wrote earlier:

"I will just state that the "electronic 
dosimeter" can only be considered viable for "dose of record" if the 
working environment is stable, the spectra in which the worker is 
exposed does not change, and that the calibration factors don't 
change, based on all of the above. Experience has demonstrated 
that this is not often the case. The fact that the primary spectra 
happens to be high energy photons, with whatever beta spectra 
you have within your facility, does not mean that when there is a 
"radiological incidence" that the spectra doesn't change. It does 
and it will. The calibration of the device drives the final dose 
determination, as well as the dose rate. When there is a change, 
the values obtained are no longer valid, and can result in  severe 
under-response, often leading to a dose that could exceed 
regulatory limits, exceed administrative guidelines, etc. In essence, 
while the manufacturers swear that the "electronic dosimeter" is 
not a processing dosimeter, such as found with dose determination 
from a film or TLD, it is just that. There are built in algorithms and 
parameters set and those that are hidden, within the device, and if 
those factors changes, so does the final dose reported."

Sandy- Your last sentence had me wondering- What's the difference between an
electronic dosimeter running its own internal algorithms to determine
radiation type, energy and dose, and a dosimetry vendor applying ITS
algorithms to a film or tld badge to determine radiation type, energy
and dose?  Are you saying that in some way the vendor's combination of
dosimeter and algorithm is inherently superior?  If so, how?

Also, your statement about changes in radiation environment leading
to possible overexposures because the epd underresponded seems a bit too
alarmist to me.  Before you purchase any kind of epd OR dosimetry service,
you need to ensure the dosimeter can handle the various radiations
that could be encountered.  Assuming you have done that homework, would
you still stick by your statement? 

We have used Landauer for our dosimetry of record for years, and I trust
their results.  We have also used Siemens EPD-2's for several years as an
additional tool to assist with exposure monitoring and control, and I
have been very impressed with their capabilities as well, so perhaps I'm
biased.

My opinions only.

John Laferriere, CHP
DuPont Pharmaceuticals Co.
Medical Imaging Division
John.R.Laferriere@dupontpharma.com

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html