RE: Minimum Detectable Activity

[fbronson@canberra.com]

The simple method described by Mr North could be made reasonably correct by
dividing the "square-root of the background count" by the count time in minutes.






"North, David" <DNorth@Lifespan.org> on 06/14/2000 10:03:09 AM

Please respond to radsafe@romulus.ehs.uiuc.edu

 To:  Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
 cc:   (bcc: Frazier Bronson/CI/US/PBC)
 Subject:  RE: Minimum Detectable Activity




A simple method for finding your MDA for a radionuclide to 99% confidence:
Determine the counter's sensitivity in "counts/time/activity", e.g. cpm/uCi.
Take a background count for the same time you will use for your sample
counts. Take the square-root of the background count to estimate the
standard deviation, multiply by 3 and divide by your sensitivity. The answer
will be your MDA in units of activity.

David L. North, Sc.M. DABR
Providence, RI 02903






---------------
Frazier Bronson CHP
Canberra, 800 Research Pkwy, Meriden CT 06457 USA
tel: 203-639-2345 e-mail: fbronson@canberra.com


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