Re: Clarification: Efficiency for detection of Tc-99m

[Kerembaev@cs.com]

John,

Do you need to know efficiency for Tc-99m in vivo also? 
Or just the surface contamination?

Vivo or Vitro?
That one always was a hard one for me to remember.

1. For in vivo:
Assuming that you know how much Tc-99m was administer.
The only way to know the true "EFFICIENCY" per administer unit.
Just calibrate the (GM) Pan Cake for each procedure.
The size and sex of the patient will make some difference too.
But that all just does not make sense. Why do you need that?
You have the imaging camera. What possibly could have more efficiency.

2.
Surface contamination.
I always used 1%. It is not so important to know that its 0.5 or 1.8%.
Most of times, as you of course know, nobody is cleaning Nuc.Med. Tc-99m 
spills. So 
you wait until it drops to "BGRD" 

If I REALLY need to know the efficiency.
I would just calibrate one meter. 

I hope, this will help but not confuse.

Emil.
kerembaev@cs.com





In a message dated 1/21/00 7:37:17 Pacific Standard Time, 
JJacobus@exchange.nih.gov writes:

<< 
 Please note that Tc-99m is used in nuclear medicine studies for in vivo 
imaging.
 It emits photons and conversion electrons.
 
 Can anyone give me a reasonable detection efficiency for measuring Tc-99m
 surface contamination using a GM pancake type probe?
 
 -- John
 
 John Jacobus, MS
 Health Physicist
 National Institutes of Health
 Radiation Safety Branch, Building 21
 21 Wilson Drive, MSC 6780
 Bethesda, MD  20892-6780
 Phone: 301-496-5774      Fax: 301-496-3544
 jjacobus@exchange.nih.gov (W)
 jenday@ix.netcom.com (H)
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