biodex ATOMLAB 500, Руководство по эксплуатации и обслуживанию, Страница: 174 / 212

Replace the equation with following:
A = A
0
/ 2
n
A = 43 mCi / 2
(0.8833/6.007)
A = 43 mCi / 2
(0.1470451)
A =
43 mCi / 1.1072992
A = 38.83 mCi
Decay Factor Method
The following method is used to perform radioisotope decay calculations using a calculator
without the e
x
function:
1. Measure the current activity A
i
if the radioisotope.
2. Look up the half live (T
1/2
) of the radioisotope. Note the time units.
3. Calculate the time t in the same units as the (T
1/2
) that will elapse between the time the
activity measurement was made and the time at which the decayed activity of the
radioisotope must be known.
4. Calculate
𝑡 ÷ 𝑇
! / !
in terms of N + R, where N is an integer (0, 1, 2, …n) and R is less than 1.
5. Look up X
n
(N) in Table D.1.
6. Look up X
r
(R) in Table D.2. Decay Factor Chart.
7. Calculate
𝐴
!
= 𝐴
!
× 𝑋
!
𝑁 × 𝑋
!
𝑅
=
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:
A
0
= 43mCi.
For Tc-99m, T
1/2
= 6.007 h.
t = 32.5 h.
! !
!
! / !
= 32.5 h ÷ 6.007 = 5.410.
N = 5
R = 0.410.
From Table D.1, X
n
(5) = 0.03125.
From the Decay Factor Chart, the .41 row and the .000 column, X
r
(.41) = .75262.
𝐴
!
= 𝐴
!
× 𝑋
!
𝑁 × 𝑋
!
𝑅