biodex ATOMLAB 960 - Page 225

ATOMLAB 960 MEDICAL SPECTROMETER APPENDIX E E-7
Explanation Of Decay Calculation Methods
CALCULATOR METHOD
The radioactivity of an isotope can be calculated as it decays using the following expression:
A
f
= Ai e
-λt
where
A
f
= final activity at the end of the decay time;
A
i
= initial activity measured at some starting time;
t = net decay time in units inverse to λ; and
λ = (lamda) decay constant specific to the radioisotope.
λ = ln (2) / T
1/2
= 0.693 / T
1/2
where
T
1/2
= half life specific to the radioisotope.
So, using a calculator with the ex function, decay calculations can easily be performed, as
shown in the first section of this appendix.