RE: Constant for F-18

["Michael Stabin" <stabin@npd.ufpe.br>]

 Bruce Heinmiller said:
> If they specified "gamma constant", I'm a bit dubious about a reference
that
> talks at the same time about a gamma ray constant and which x-rays were
> excluded!  Many errors have been made (OK, maybe not with F-18) confusing
> two related but quite different quantities - specific gamma constant and
> specific exposure rate constant.

This value (5.73 R-cm2/mCi-hr) was calculated by staff at the Radiation
Internal Dose Information Center in Oak Ridge, using a program that
calculates what should be referred to as an exposure rate constant, I agree.
The center was asked by the FDA to calculate these numbers for use in
nuclear medicine with and without the inclusion of some low energy photons,
as these can often be assumed to be mostly attentuated by glass vials and
other containers in many cases.  Values were also calculated with all photon
emissions included, and the various users (e.g. Mallinckrodt) chose which
values they would report with their products and the terminology with which
to express them.

I still have a table of about 200 nuclides generated in this way, which also
includes calculations of lead attenuation factors (0.5, 0.1, 0.01, 0.001,
0.0001), and I can provide it to interested parties.  The data and
documentation on the program (developed by Evelyn Watson and Audrey Stelson)
were unfortunately never published, so they can only be referred to as a
personal communication.  This perhaps doesn't carry the same weight as some
published values, but I believe them to be quite sound.


Michael Stabin, PhD, CHP
Departamento de Energia Nuclear/UFPE
Av. Prof. Luiz Freire, 1000 - Cidade Universitaria
CEP 50740 - 540
Recife - PE
Brazil
Phone 55-81-271-8251 or 8252 or 8253
Fax  55-81-271-8250
E-mail stabin@npd.ufpe.br

"Quantum Mechanics: The dreams stuff is made of"
- Steven Wright


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