Here's how to determine the Activity present after a certain amount of time passes (nuclear decay formula) without having to use the constant e (Euler's number):
A(t) = A(0) * 2 ^ (-t/halflife)
Activity at time "t" =
Activity at time zero
TIMES
2 raised to the [ (-t) / halflife]
This is much more simple than having to use the constant e
e.g.
What is the activity after 6 hours for 10 mCi of Tc99m ?
A(t) = the unknown
halflife = 360 minutes for Tc99m
t = 360 minutes
A(0) = 10 mCi
2 raised to the (-360/360) = 2 raised to the -1 = 1/2
therefore....
A(t) = 10 * 1/2 = 5 mCi
A = Ao * 2 ^ (-t/halflife)
much more simple!
This is how I was taught in 1993 and it is much more simple than using e
- Tom Heston
