RE: Gamma Ray Constant for F-18

[Rosen_Jerry <rosen@radsafe.pitt.edu>]

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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