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Strom Daniel J.; Stansbury, Paul S.
Health Physics: September 1992
Notes: PDF Only

This note discusses the use of blank or background counting data that are measured for times that differ from times used for the sample counts. The correct formula for the minimum detectable activity, under this condition, is given as follows: MDA = [3 + 3.29 SQRT(Rbtg(1 + tg/tb)])/etg, where Rb denotes background count rate, tb and tg denote background and gross count times, and e denotes counting efficiency. Counting backgrounds for a long time reduces decision levels, uncertainties, and minimum detectable activities. These benefits are fully available only when there is no other source of variability than random fluctuations in count rates.

©1992Health Physics Society