RE: Gamma Ray Constant for F-18

["Heinmiller, Bruce" <heinmillerb@aecl.ca>]

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