Fwd: Palladium Calibration

[Ccja@aol.com]

I forward this note with the permission of the sender.

chris alston
---------------------
Forwarded message:
From:	radsafeo@VAX.CS.HSCSYR.EDU (Radiation Safety Offic)
To:	ccja@aol.com
Date: 97-10-08 09:33:01 EDT

Chris,

I noticed the same thing. We have only received 5 shipments with 2 being at
72% and the last 3 at 54%. I noticed it because since we don't have that
many inplants and that they are new, I look up the number each time. The
change was made between 6/24 and 8/26.

Pete

> On a related question, someone asked or posted a comment some time ago,
about
> the correct multiplicative conversion factor to use when calculating the
> actual activity of contained Pd103, in a Theragenics seed. I think that
> someone stated that an individual at Theragenics had quoted a factor of
2.3,
> telephonically, but without any citation of reference. An examination of
the
> basic data sheet for the seeds (which typically accompanies a shipment)
> reveals the following statement (fourth sentence, under "Actions", top of
> second column, first page).
>
> "Total attenuation resulting from titanium encapsulation, x-ray marker, and
> self absorption from the Pd-103 pellet is approximately 54% on average." I
> read this to mean that the "apparent activity" represents 46% of the
> contained activity, ergo, for the purposes of inventory, we should multiply
> the apparent activity by the inverse of that number, i.e., 2.17 (or 2.2, if
> you prefer), to obtain the "true" activity of the seeds. That is, the
> quantity that the regulatory folks want to see. If anyone finds this
> reasoning fallacious, please don't hesitate to let us know ASAP.
>
> As an aside, I could have sworn that, six months or more ago, the figure
> given for total attenuation was 72%, thus we've been using a conversion
> factor of 3.6 (1/28%). The result being a 64% overestimate!! I've got to
find
> that document; I can't believe that I made that number up out of whole
cloth.
> Thanks again to Mary Ellen for waving a yellow flag over the calibration
> issue.
>
> chris alston
> ccja@aol.com

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