The Detector Efficiency (D.E.) has been calculated for both probe and well detectors. There is a difference
because the photon path length through the Nal detector is different in the two detector configurations.
There are some isotopes that the well efficiency has not been analytically determined due to gamma ray
summing in the well. You must use the empirical method for these isotopes. You may have to create a
custom version of the isotope with a different ROI to properly count the isotope in the well.
Analytically Determined Detector Efficiencies
Please refer to this table below for Analytically Determined Detector Efficiency (%) settings on the
following Atomlab products: Thyroid Uptake Models 930 and 950, Wipe Test Counter Model 450.
Probe Well
Isotope Left-ROI Right-ROI Efficiency Efficiency
Na-24 1162 3167 7.8 ——
K-42 1296 1754 0.9 0.4
Cr-51 272 368 6.7 4.5
Co-57 103 158 93.8 92.8
Co-58 434 933 24.1 ——
Co-60 997 1533 14.2 ——
Fe-59 934 1486 7.7 3.8
Ga-67 79 345 72.8 ——
Se-75 102 461 148.9 ——
Sr-85 437 591 32.6 18.2
Tc-99m 119 162 84.3 82.3
Pd-103 17 27 62.3 62.3
In-111 145 281 163.4 138.7
I-123 134 183 79.4 75.4
I-125 23 41 133.5 133.5
I-131 309 420 47.4 30.1
Ba-133 256 410 60.8 ——
Cs-137 561 761 18.2 9.7
Yb-169 41 228 312.4 ——
Ir-192 250 703 124.6 ——
Hg-197 56 90 89.1 89.1
Hg-203 237 322 62.8 44.8
Ti-201 57 96 93.2 ——
Au-198 349 474 46.4 28.0
Am-241 50 69 35.7 35.7
F-18 408 613 35.97 18.55
NOTE: It is recommended that users use the Empirical testing procedures for setting detector efficiency.
Revised 6/05
1. INTRODUCTION
A-7 APPENDIX A
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