RE: Gamma Ray Constant for F-18

["Boyce, Dale" <DBoyce@intiso.com>]

	I always thought it was semantics.  The symbol for a dose constant
is capital gamma.  Folks sometimes call it gamma constant due to the symbol
representing it. Most of the references I've run across include x-rays
usually with a 10 or 20 kev cutoff.  Afterall it is the dose or exposure due
to photons that we are nominally interested in. 

	Dale Boyce
	International Isotopes Inc

> -----Original Message-----
> From:	Rosen_Jerry [SMTP:rosen@radsafe.pitt.edu]
> Sent:	Monday, January 31, 2000 3:42 PM
> To:	Multiple recipients of list
> Subject:	RE: Gamma Ray Constant for F-18
> 
> You shouldn't be dubious. Exposure constatnts and gamma constants are two
> different animals. Further annihilation photons are not gammas. They do
> not
> originate in the nucleus. Although publications like Kocher's, radioactive
> decay tables, list annihilation photons as Gamma+-, they are specifically
> separated from the gamma listings.
> 
> -----Original Message-----
> From: Heinmiller, Bruce [mailto:heinmillerb@aecl.ca]
> Sent: Monday, January 31, 2000 3:45 PM
> To: Multiple recipients of list
> Subject: RE: Gamma Ray Constant for F-18
> 
> 
> 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.
> 
> Bruce Heinmiller CHP
> heinmillerb@aecl.ca
> 
> > ----------
> > From: 	David Whitfill[SMTP:DWhitfil@kdhe.state.ks.us]
> > Reply To: 	radsafe@romulus.ehs.uiuc.edu
> > Sent: 	Monday, January 31, 2000 3:19 PM
> > To: 	Multiple recipients of list
> > Subject: 	Re: Gamma Ray Constant for F-18
> > 
> > 
> > 
> > I just ran across a data sheet prepared by Mallinckrodt which gives the
> > gamma constant for F-18 as 5.72905 R-cm^2 per h-mCi. There is a note
> which
> > says the calculations exclude all X-rays < 20 keV.
> > 
> > ============================================
> > The handbook of Health Physics and Radiological Health, 3rd ed., gives
> > this
> > value for F-18:
> > 
> > 1.879E-04 mSv-m^2 per h-MBq = 6.95 rem-cm^2/h-mCi
> > 
> > If you assume 1 rem = 1 rad = 1 R you're finished, but..
> > 
> > X air, R = D tissue, rad/(0.87 rad/R) x (uen/p air)/(uen/p tissue)
> > 
> > Using an energy of 500 keV (close to 511 keV), the energy-absorption
> > coefficients are 2.966E-02 cm^2/g for air and
> > 
> > 3.304E-02 cm^2/g for adipose tissue (RHH 5-24,25) and the correction
> > factor
> > with 1 rem = 1 rad is 1.03:
> > 
> > 7.16 rem-cm^2/h-mCi
> > 
> > =============================================
> > >I am looking for the true Gamma Ray Constant for F-18 in the nostalgic
> > units of R/hr-cm^2/mCi.  There have been values reported in the range of
> > 5.7 - 8.  Can anyone pin it down for me?
> > >
> > Scott Dube
> > sdube@queens.org
> > 
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