biodex ATOMLAB 500, Руководство по эксплуатации и обслуживанию, Страница: 204 / 212

Record the values on the Linearity form (see Figure J.1). Calculate the activity correction
factors (
cf ) by dividing the average of all decay corrected measurements ( M
0
) by each ( M
0
):
𝑐𝑓
!
=
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑜𝑓 𝑎𝑙𝑙 𝑀
!
𝑀
!
𝑡
Accept the result if it is within the range of 0.95 <
𝑐𝑓
!
<1.05. Consider correcting the
displayed activity measurement ( M ) of radio pharmaceuticals if a linearity error is greater
than ± 5% and less than ± 10% (i.e., 0.90 <
𝑐𝑓
!
<0.95 or 1.05 <
𝑐𝑓
!
<1.10. Corrected
M = M × 𝑐𝑓
!
where the subscript M is the closest in value to M in the most recent linearity
form. For low activity values, if 𝑐𝑓
!
< 0.95 refer to the following note concerning Mo-99
contamination.
Note: If there is any Mo-99 contaminant in the Tc-99m sample, long decay times (>48h) will
compromise the decay linearity test. The contamination will become apparent with
decreasing
𝑐𝑓
!
values for the lowest displayed activity measurements ( M ). In order to test
for this, prepare another linearity test sample with an activity of approximately 1 mCi .
Repeat the linearity test. If the 𝑐𝑓
!
values are within an acceptable range and if the first
linearity test by decay produced acceptable 𝑐𝑓
!
values at higher M values, the dose
calibrator passes. The two linearity tests should have overlapping activity values in the
acceptable range.
1
Hint: Recalculate the first test ( M
0
) without including failing values from
low ( M ) M0-99 contamination.
5. If
𝑐𝑓
!
< 0.90 or > 1.10, contact Biodex technical support and provide full details including all
linearity decay data.
Attenuation Tube Method or Sleeve Test Method:
If it is decided to use a set of sleeves of various thicknesses or a combination of sleeves to test
for linearity, it is necessary to first use the Decay Method to ensure the calibrator is linear. Once
proven, immediately repeat the test. Follow the directions furnished with the lead sleeves (i.e.,
Lineator instructions).
If a failure occurs at the low activities, check for Mo-99 contamination by repeating the test with
1
mCi (see the note under Decay Method in step 4 above).
Note: The Sleeve Test procedure can be performed first and immediately afterwards a
traditional Linearity test can be performed. Doing this allows the user to perform both tests
with one dose.
Note: Other isotopes can be used to perform linearity (e.g., F-18). The sleeves may only be used
with Tc-99.
1
See Quality Control Testing of Dose Calibrators, R.Y.L Chu and W.E. Simon, Journal of Nuclear
Medicine Technology, 24 #2, June 1996, pp 124-128.