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Dose Calibrator

My dose calibrator has failed the linearity test, what should I do?

The great majority of linearity failures are due to operator errors. Of all the calibrators serviced by Capintec, only a rare few were non linear. For the older analog units, first check the battery voltage (150V), next adjust the zero and then background. For microprocessor calibrators first run the daily test and insure that all tests are within expected limits. Repeat the linearity test using the decay method. Carefully record the actual time (not the expected time) using the same clock or calibrator clock for each measurement. For low activity measurements, insure that no sources or other activity is near the calibrator. If a linearity test fails using a Calicheck system, repeat the test using the decay method. Calicheck correction factors must be measured independently for each dose calibrator and for each set of sleeves.

What does the calibration number mean? The source has a large error using the calibration number in the manual, what is wrong?

All calibration numbers are based upon the NIST (NBS) geometry, which is 5 ml of solution in a flame sealed glass ampoule with 0.6 mm wall thickness. This geometry provides a good estimate for most commonly used radiopharmaceuticals in vials or plastic syringes. For isotopes with significant abundance of low energy photons, pure beta emitters or different geometries such as capsules, wires or seeds, geometry correction factors are required. Request a NIST traceable sample from the source manufacturer and use the sample to determine the correct calibration number. Many times the source manufacturer can also provide a calibration number for Capintec dose calibrators and for their unique source configuration. For some sources, an ADCL lab can also provide a highly accurate calibration number. Due to the large number of available vials and syringes and the lack of standardization of containers in the radiopharmacy industry, Capintec does not supply calibration numbers for different geometries. It should also be noted that the same or similar geometry for the same isotope supplied by two different manufacturers may also require two different calibration numbers.

How do I set up a user key on my 15 family dose calibrator?

Under the UTIL menu, select SETUP. Press 4 for other. Enter Password. Select User Keys. Select the desired user key, U1...U5. Then type in the nuclide.

My accuracy test is failed, what is the problem?

First confirm that the calibration date entered into system is correct. Since the system uses a default date as an example, users occasionally forget to change the year.

The accuracy test of my 15W well exceeds 5%, what should I do?

First, perform an autocal. The software automatically adjusts the gain to compensate for normal drift of the NaI detectors. Over time as detectors age, the systems may drift out of the autocalibration range. The user must then make a simple manual adjustment using a small screwdriver to the calibration pot using a check source. A detailed manual calibration procedure is available from your Capintec Application Specialist. Recent engineering changes have extended the automatic calibration range and eliminated the need for manual adjustments. 15Ws with serial numbers greater than 170925 have the new extended calibration change. Older units may also be upgraded at the Capintec Service Center.

How do I determine the efficiency of an isotope on my 15W well?

The 15W well uses the term conversion factor, which is the inverse of efficiency, to convert count rates to activity. 15W wells have nominal conversion factors for most commonly used isotopes in the software. These default values will provide a +/- 10% to 15% accuracy for a wide variety of wipe test methods, e.g. alcohol wipes, cotton tipped swabs, tissue paper in test tubes, etc. Alternately, a generic conversion factor of the most common isotopes (Tc-99m) or a check source can be used to estimate the activity of all isotopes. To improve accuracy or determine the conversion of an isotope not listed in the database, prepare an aliquot with < 1 uCi activity. Then, in the UTIL menu select CONV FACTOR and follow the prompts. The system will automatically measure, calculate and store the new conversion factor.