Re: ? renal scan dose

[Bob Dunn <rso.gscancer@worldnet.att.net>]

John Zummo wrote:
> 
> A PI just called to tell me that yesderday one of her lab workers had a
> Tc-99m renal scan at 9AM, and then came to work at 11AM.  She spent most
> of the day at the PC, about 3-4 feet away from the badge rack where the
> dosimeters for the lab are kept.  She herself is not a radiation worker.
> The PI reported that the person was "quite hot" by the GM meter.  She did
> not know what the administered dose was, but was now concerned about the
> badges.
> 
> My limited nuc med references show a typical dose of 20 mCi, with a post
> administration dose rate of 2 mrem/hour at 3 feet.  If this is correct,
> the badges should show less than 10 mrem.
> 
> Can any nuc med experts confirm this, or am I missing something?
> 
> Thanks in advance.
> 
> Regards,
> 
> John
> 
> John Zummo, RSO
> Genentech, Inc.
> (415) 225-2959
> (415) 225-5008 (fax)
> zummo@gene.comDear John,
As a rule of thumb, the dose to total decay can be calculated as 
follows:
		D = 34.6*n*Specific Gamma Ray Const.*T1/2p(1)/r^2
Where, 34.6 = Conversion factor of 24 hrs/day*1.443
	
	n = Activity Admistered (can be found out from institution exam 
	was performed at

	SPGC = 0.756 for 99m-Tc

	T1/2p = Physical Half-life (99m-Tc = .251 days)

	r = distance (usually 100cm^2 ~ ~ 1 meter
I hope this helps, if you have any other questions, please feel free to 
get in touch with me.
Bob Dunn
rso.gscancer@worldnet.att.net
201-844-7111
201-603-1228 - pager