B
iodex Medical Systems Quality Assurance Testing of AtomLab
®
Dose Calibrators
July 8, 2004 P/N 107012 Rev. B; © 2004, Sun Nuclear Corp. page 2 of 4
Linearity
Linearity means the proportionality of the
measurement result to the activity mea-
sured, as determined over the intended
range of use for the dose calibrator.
This test is done using a vial or syringe of
T
c-99m whose activity is at least as large as
the maximum activity normally assayed in
a prepared radio pharmaceutical kit, in a
unit dosage syringe, or in a radio pharma-
ceutical therapy, whichever is largest.
D
ecay method
1
Zero the Background by pressing the
Background (Bkgnd) button.
2 Assay the Tc-99m syringe or vial in the
d
ose calibrator to obtain the activity.
This first assay should be done in the
m
orning at a convenient time, for exam-
ple, 8 A.M.
3 Repeat steps 1 and 2 at about noon and
again at about 4 P.M. Continue on sub-
s
equent days until the displayed activity
is ten (10) microcuries or less. If the dis-
play indicates less than 50 µCi, (1.85
MBq), wait 30 seconds before recording
the display. Or, press the Mo-99 key on
the AtomLab panel and then the Tc-99m
key to get a faster reading. Record the
date, time (to the nearest minute), and
activity.
NOTE: Use of a spreadsheet, such as Microsoft
Excel, in steps 4 and 5 will simplify
calculations.
4 Convert the time and date information
you recorded to hours (t) elapsed since
the first assay. Decay-correct each dis-
played activity measurement (M) using
the equation,
,
where T
1/2
= 6.007 h. Record the values .
See linearity form, Figure 1. Calculate
activity correction factors (cf) by divid-
ing the average of all decay corrected
m
easurements ( ) by each M
0
, i.e.,
.
Accept if 0.95 < cf
M
< 1.05. Consider
correcting the displayed activity mea-
surem ent (M) o f ra dio pharmaceuticals if
a
linearity error is greater than ± 5% and
less than ± 10%, i.e., 0.90 < cf
M
< 0.95
o
r 1.05 < cf
M
< 1.10. Corrected M = M
* cf
M
where subscript M is closest in
v
alue to M in most recent linearity form.
For low activity values, if cf
M
< 0.95 see
the following note about Mo-99
contamination.
NOTE: If there is any Mo-99 contaminant in
the Tc-99m sample, then long decay tines
(>48h) will compromise the decay linearity
test. This will be apparent with decreasing
cf
M
values for the lowest displayed activity
measurements (M). In order to test for this,
prepare another linearity test sample with
an activity of about 1 mCi. Repeat the lin-
earity test. If the cf
M
values are within an
acceptable range and if the 1st linearity test
b
y decay produced acceptable cf
M
values at
higher M values, then the dose calibrator
passes. The two linearity tests should have
overlapping activity values in the acceptable
range.
3
Hint: Recalculate first test ( )
without including failing values from low
(M) Mo-99 contamination.
5 I
f cf
M
< 0.90 or > 1.10, contact Biodex
t
echnical support and provide full
details, including all linearity decay
data.
6 Put a sticker on the dose calibrator that
says when the next linearity test is due.
S
hield method
If you decide to use a set of “sleeves” of
various thicknesses or combination of
sleeves to test for linearity, it will be nec-
essary to first use the Decay Method to
show the calibrator is linear. Then follow
the directions furnished with your lead
sleeves (i.e. Lineator instructions.)
If failure occurs at the low activities, check
for Mo-99 contamination by repeating the
test with 1 mCi. See Note under “Decay
Method,” step 5.
Geometry
Geometry Independence means that the
indicated activity does not change with
volume or configuration of the source
material. This test should be done using a
syringe that is normally used for injec-
tions. The following test assumes
injections are done with 3 ml plastic
syrin ges an d that r adio p harma ceuti cal kit s
are made in 30 ml glass vials. If you do not
use these, change the procedure so that
your syringes and vials are tested through-
out the range of volumes commonly used.
If a significant volume correction results
from these procedures, the tests should be
M
0
M2()
t
T
12⁄
----------
⋅=
M
0
cf
M
Average of all M
0
M
0
t
()
-------------------------------------------=
3. See “Quality Control Testing of Dose Calibra-
tors,” R.Y.L. Chu and W. E. Simon, Journal of Nu-
clear Medicine Technology, 24, #2, June 1996, pp
124-128.
M
0
AtomLab Dose Calibrator Linearity Test, Model: _______________ Serial Number:_______________
Date Time Activity Measured, M Hours elapsed, t
M
0,t
cf
M
= Avg / M
0,t
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
______ ______ ______ ______ ______ ______
Avg: ______
Accept if 0.95 < Avg / M
o,t
<1.05
Figure 1. Sample dose calibrator linearity test data collection form
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