[ RadSafe ] SELECTED MINIMAL REPORTING LIMIT (SL)

[Sandy Perle]

On 26 Aug 2005 at 16:57, Herren, Roy WS. wrote:

> One of the options offered by a commercial Dosimetry vendor with their
> RADIATION DOMIMETRY REPORT is a "SELECTED MINIMAL REPORTING LIMIT (SL)
> of 10 mRem.  Their general information section on the back of their
> reports state: "SL" is an elective option for the minimal dose
> equivalent reported for the dosimeter for photon (x and gamma ray).
> Exposures less than 10mrem report as "SL", and exposures at or more
> than 10 mrem begin reporting at 10 mrem and report in increment of 10
> mrem.

GDS does not offer selective minimal reporting limits. The Lower 
Limit of Detection is determined for each dosimeter type, and a 
representative Minimum Reportable Dose (MRD) is provided based on the 
statistics involved. It is a potential litigation issue if a higher 
MRD is used when in fact the actual dose that a dosimeter can detect 
and accurately report is used. This is considered under-reporting a 
dose. I would suspect that regulators would have a problem with that. 
On the other hand, using a lower MRD when the statistics aren't valid 
is also an issue, with a higher probability of false positives.

GDS reports dose to the next integer; i.e, 12, mrem, 13 mrem, etc. We 
don't round up or down to the next 5 mrem or 10 mrem. We round up to 
the next higher integer. This is the most accurate method. Rounding 
up or down 5 mrem or 10 mrem increments is not significant at high 
doses, but at 10 mrem we're talking about 50% or higher variation. 
Not acceptable in my opinion. 

> >From an accuracy stand point, is the utilization of the "SL" option
> >of
> setting the bar, so to speak, at 10 mrem scientifically defensible?
> What about the report incremental increase of 10 mrem?  What is the
> benefit of the usage of "SL", and what is the detriment?

To reiterate, the MRD should be based on statistical analysis, 
considering the overall measurement of uncertainty assessing all 
appropriate influence quantities. I've stated my opinion and our 
practice based on real statistics.


----------------------------------------------------------------
Sandy Perle 
Senior Vice President, Technical Operations 
Global Dosimetry Solutions, Inc. 
2652 McGaw Avenue
Irvine, CA 92614

Tel: (949) 296-2306 / (888) 437-1714 Extension 2306 
Fax:(949) 296-1144

Global Dosimetry Website: http://www.dosimetry.com/ 
Personal Website: http://sandy-travels.com/