Physics and Radiobiology of Nuclear Medicine

tion (current) produced by different radionuclides so that equal activities
produce the same reading. In most dose calibrators, isotope selectors for
common radionuclides are push-button type, whereas those for other
radionuclides are set by a continuous dial. An activity range selector is a
variable resistor that adjusts the range of activity (mCi, mCi, Ci, or kBq,
MBq, GBq) for display.
In the past, the NRC required the calibration of dose calibrators for con-
stancy, accuracy, and linearity of their operation and geometry of samples
and accordingly prescribed specific recommendations for these tests.
However, current NRC regulations (10CFR35) require only to have these
calibrations performed according to nationally recognized standards or the
manufacturers’ instructions. In the absence of specific recommendations,
the earlier frequency and other related requirements of these calibration
tests have been given as follows:

1. Constancy (daily)


2. Accuracy (at installation, annually, and after adjustment or repairs)


3. Linearity (at installation, quarterly, and after adjustment or repairs)


4. Geometry (at installation and after adjustment or repairs)

Ionization Chambers 75

Fig. 7.3. A typical dose calibrator. (Courtesy of Capintec, Inc., Ramsey, NJ.)