[ RadSafe ] Any suggestions for a nuclear medicine wipe counter?

[garyi at trinityphysics.com]

Yes, someone already pointed out that a pancake would be more efficient for betas.  And I 
also agree with you that:

    "All it does is determine if the smear exceeds a
    certain number of count in the preset interval.  If
    not, then the smear "passes."  "

The gist of my post was that the counter does not seem to be adequate for gamma emitters 
like Tc99m, if you wish to determine with 95% confidence that a wipe test for removable 
contamination was less than 1000 dpm / 100sq.cm 

-Gary

On 25 May 2007 at 9:32, John Jacobus wrote:

Date sent:      	Fri, 25 May 2007 09:32:26 -0700 (PDT)
From:           	John Jacobus <crispy_bird at yahoo.com>
Subject:        	Re: [ RadSafe ] Any suggestions for a nuclear medicine wipe 
counter?
To:             	garyi at trinityphysics.com, rADSAFE <radsafe at radlab.nl>

Gary,
I am not sure what you are talking about.  As it is a
GM probe, it can much better for I-131.  Tc-99m does
not emit beta particles, while I-131 does.  

All it does is determine if the smear exceeds a
certain number of count in the preset interval.  If
not, then the smear "passes."  


--- garyi at trinityphysics.com wrote:

> Hi John, 
> 
> Thanks for your suggestion. I've never used that
> counter, but it seems like it would be awfully 
> close to or perhaps over the 1000 dpm/100 sq cm
> limit. You may have used it with no 
> problems, but I played with the numbers listed on
> the web page you kindly sent me. At 6 
> cpm/kdpm efficiency for Tc99m, and with the
> "Background Voltage" of up to 24 cpm, it can 
> do better than 1000 dpm, but only if you count for
> the max count time of 20 minutes. And I 
> wonder if "Background Voltage" refers to counts due
> to voltage/electronics and not external 
> field. The downloadable information is rather vague.
> 
> 
> Since I'm trying to help someone who is using mostly
> I131, which probably counts less 
> efficiently on this GM, I will probably keep
> looking. But like I said, I haven't used it before 
> myself so please let me know if you have tried it
> and liked it. 
> 
> Thanks again, 
> Gary 
> 
> On 20 May 2007 at 17:39, John Jacobus wrote: 
> 
> Date sent:  Sun, 20 May 2007 17:39:42 -0700 (PDT) 
> From:  John Jacobus <crispy_bird at yahoo.com> 
> Subject:  Re: [ RadSafe ] Any suggestions for a
> nuclear medicine wipe 
> counter? 
> To:  garyi at trinityphysics.com, RADSAFE
> <radsafe at radlab.nl> 
> 
> Gary, 
> Try this. The Wipe Counter (Model 1051). It uses a
> GM 
> detector system, and is easy to operate, i.e., 
> pass/fail. I think that the NRC approved its use
> many 
> years ago. 
> 
>
http://www.biodex.com/radio/sampling/sampling_586.htm
> 
> 
> or 
> 
>
http://www.sunnuclear.com/Products/WipeTestCounter/wipetest.asp
> 
> 
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+++++++++++++++++++
What are the facts? Again and again and again - what are the facts?
Shun wishful thinking,. . . avoid opinion, [and] care not what the
neighbors think, . . .what are the facts, and to how many decimal
places? You pilot always into an unknown future; facts are your single
clue. Get the facts!" 
 "Time Enough for Love," Robert Heinlein, 1973

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com



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