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216 ATOMLAB 500 DOSE CALIBRATOR
Dial Settings For Y-90
The typical Atomlab 500 Dose Calibrator dial setting for Y-90 activity in a 10 cc plastic syringe is
350. This value can be used as a starting point for initial measurements. However, it is
recommended that the dial setting used for clinical measurements be determined from the first
dose of Zevalin received from the radiopharmacy, as outlined below. Following doses should then
be compared to the radiopharmacy doses for constancy.
The Y-90 recipient, using an Atomlab Dose Calibrator, should determine the correct dial value
from the first Y-90 dose that they receive from a commercial radiopharmacy. This is determined by
selecting the Y-90 button and adjusting the dial setting until the displayed activity agrees with the
decay corrected Y-90 syringe activity as stated by the commercial radiopharmacy. If the
adjusted dial setting falls within the range of 333 to 368, then use that dial setting.
If It Falls Outside The Range, Verify That:
• there is a well liner in place
• a hook style dipper is used
• the annual accuracy and Daily Constancy Test results are acceptable
If these criteria are met, then determine the percent difference of the new dial value with
respect to the nearest range limit value (333 or 368), i.e. dial value error (DVE). Add this per-
cent to the change in constancy percent error (CCPE). If the sum of the errors is in the range of
-2% to +2%, then the new dial value should be used. If not, contact Biodex Technical Support.
The user may also want to contact the radiopharmacy to determine if a calibration error may
have occurred.
NOTE: The CCPE is the percent change from calibrator installation of the constancy
measurement, where CCPE = "Today's" Constancy Percent Error - "Installation's" Constancy
Percent Error. The Constancy Percent Error is the measurement error with respect to the decay
corrected source activity. A change down in the Atomlab Calibrator constancy will cause a change up
in the dial value required to compensate the change in constancy, and visa-a versa. Thus, the CCPE
will have the opposite sign as the DVE, so adding them should cancel to within 2%.
For example, a new dial value for Y-90 is found to be 374. This falls outside the range and is
+1.5% higher than 368. The constancy measurement shows a -2.5% change since the dose
calibrator was installed. Their sum is (+1.5%) + (-2.5%) =
-1.0%, which within -2% and +2%. The dial value of 374 should be used.
NOTE: For all Atomlab Dose Calibrator models, the well liner must be installed before
making measurements. The well liner provides attenuation for the Y-90 betas that
would otherwise enter the detector and cause high readings.
NOTE: The dial value range provided above is for use with plastic syringes; due to the wide
variation in styles between vials it is recommended that the user determine the dial value for
vials themselves. This can be done using a vial containing a known activity of Y-90, by
changing the dial value until the activity read using the Y-90 button matches the known activity
within the vial.
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