Capintec CRC-712MH, Руководство пользователя

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CAPINTEC, INC. CRC
®
-712MH
7. Record the number appearing on the Calibration Control dial.
The number recorded in Step 7 should coincide with the calibration number assigned
to the preset button used in Step 2. This can be checked by referring to the
Calibration Card supplied with the unit or Appendix II of this manual.
Well Liner Contamination
The Ionization Chamber is protected from possible contamination by a plastic liner.
This liner should be checked periodically for contamination (or any time it is suspect)
in a similar manner to that detailed in the Contamination Test (Sample Holder)
section.
Linearity Test
The linearity of the CRC
®
-712MH should be checked over the entire range of
activities which are reasonably anticipated to be used. This can be done by any of
several methods. The three most common methods are described below.
Decay Method
Start by measuring the activity of a sample of Tc99m or other nuclide of reasonably
short half-life. The activity of the sample should be at least as large as the maximum
assayed in normal use. At regular intervals, make repeated measurements of the
same sample as it decays. Continue until the activity is below the minimum assayed
in normal use.
CAUTION
Initially the activity of the Mo99 contamination in the sample will be insignificant
compared to the activity of the Tc99m. However, Mo99 has a much longer half-life
than Tc99m. If the test is continued down to very low levels, the activity of the Mo99
may become significant by the end of the test. If this is not taken into account, it may
adversely affect the results of the test.
Sleeve Method
There are several manufacturers of sets of shielding “sleeves” that may be used for
performing the linearity test. When testing by this method, follow the directions that
come with the set. Be sure that you calibrate the sleeves first.
Proportional Method
The linearity can be confirmed by measuring the activity of a sample and then
checking the activity of carefully measured portions of the sample. The activity of the
initial sample should be at least as large as the maximum assayed in normal use. The
ratio of the measured activities should be the same as the ratio of the measured
weights or volumes. The weights or volumes must be measured to a degree of
accuracy much greater than the expected linearity (i.e. ±0.5%)
5 - 4 QUALITY ASSURANCE & ACCEPTANCE TESTING December 09