| Performed by Kenneth A. Coleman,
M.E. Radiological Physicist
Conclusions:
A week-long testing of the Atomlab 100
Dose Calibrator resulted in the following conclusions.
The tests included Dose Calibrator Linearity
testing from 6-12 February 1989, Dose Calibrator Constancy
Tests over the same dates, Activity Comparisons for
many radionuclides over the same period (this data not
analyzed but provided for information), Dose Calibrator
Linearity Tests by the Attenuation Method (using the
Calicheck) performed Monday through Thursday, Geometrical
Evaluation, Vertical Variation Evaluation and Horizontal
Variation Evaluation.
The Dose Calibrator Linearity evaluation
showed an excellent linearity between 500+ mCi down
through less than 10 µCi; the daily linearity test fell
apart on the fourth day when the activity in the shield
of greatest thickness fell below 1 µCi. I am not concerned
by this performance since neither the NRC or any user
I know would ever expect a unit to function over this
range. The Calicheck Factor Calculation is provided
to show the range of correction factors that would have
resulted if the initial values were calculated that
day. The Dose Calibrator functioned well within the
requirements for linearity.
The Dose Calibrator Accuracy tests show
that the unit functions well within the required standards.
The Geometrical Variation Test indicated
a variation well within the applicable standards.
The test for Vertical Variation is an
assessment of the change in reading as a source is moved
vertically along the axis of the chamber. The system
performed in the expected manner with a slight increase
as the source neared the geometrical center of the chamber
and a significant fall off as the source left the chamber.
The system functions well.
Daily Dose Calibrator Constancy showed
an acceptable response even though the system read the
source consistently higher than its calibrated activity.
The test for Horizontal Variation shows
the effect of moving the source across the dipper well
and the system functioned well.
Regarding the unit I tested, I offer the
following comments:
1) It is an excellent decision that the
chamber and display unit are calibrated separately and
either can be returned for repair or calibration as
needed.
2) It would be helpful (and different)
if the circular depression milled in the cup at the
bottom of the dipper was made slightly larger in diameter
(not deeper) in order to allow the sealed sources used
in daily constancy tests to fit more securely in the
base. This might decrease any effect of horizontal variation
when the source tips over in the dipper or is not placed
in the hole because it doesn't sit well anyway.
My conclusion after thoroughly testing
this unit is that this system is an excellent and needed
addition to the Nuclear Medicine armamentarium and I
look forward to being able to provide this unit to clients
of Radiation Services.
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