ISOTOPE SELECTION KEY CALIBRATION
If you have an isotope whose activity has already been
accu rate ly calibrated, such as a source obtained from the
Nation al In stitute of Standards & Technology, you may use
it to set a Cal ibration Value for any of the Standard Isotope
Selection keys. The procedure is as follows.
1) Obtain the calibrated activity and its date.
For example, the National Institute of Standards &
Tech nol ogy source you obtained is I-125 with the
following properties:
Activity measured: 12/13/88, 12:00 EST
Activity per unit mass: 1.195 MBq/g ±0.005 (±0.5%)
Mass: 4.95863 g
The half-life is 59.6 days ±0.2
Let A = current activity
A
o
= activity at time of calibration
A = A
o
e
– In(2)(t/T
1/2
)
where t = time lapse since calibration and T
1/2
= half life
A
o
= (1.195 MBq/g)(4.95863 g)
= 5.926 MBq
= 160.2 µCi
t = 60.25 days
A = 160.2 e
– In(2)(60.25/59.6)
= 79.5 µCi (2.94 MBq)
2) Insert the source with Sample Holder into the Well.
3) Press any standard Isotope Selection Key. The current
Calibrated Value for the key will show in the Electronic
Thumbwheel Display. If you are calibrating for an isotope
not listed on the front panel, select the 1 or 2 key.
ATOMLAB Dose Calibrator Operation Manual Chapter 5
Biodex Medical Systems 5-6 Release 2.0
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