biodex ATOMLAB 960 - Page 222

E-4 APPENDIX E Biodex Medical Systems, Inc. © 2014
SAMPLE CALCULATION
The following is a calculation of the decayed activity of Tc-99m, with an initial activity of
43 mCi, after 32.5 hours:
1. A
i
= 43 mCi.
2. For Tc-99m, T
1/2
= 6.007 h.
3. t = 32.5 h.
4. t / T
1/2
= 32.5 h / 6.007 = 5.410. N = 5, R = 0.410.
5. From Table 1, X
n
(5) = 0.03125.
6. From the Decay Factor Chart, the .41 row and the .000 column,
X
r
(.410) = .75262.
7. A
f
= A
i
x X
n
(N) x X
r
(R) = 43 mCi x (0.03125) x (.75262) = 1.01 mCi.
N X
n
(N) = 2
-N
0 1
1 0.5
2 0.25
3 0.125
4 0.0625
5 0.03125
6 0.01563
7 0.007813
8 0.003906
9 0.001953
10 0.000977
Table 1