biodex ATOMLAB 950 - Appendices and Specifications; Isotope Efficiency Calculation

A-1 APPENDIX A
ISOTOPE EFFICIENCY CALCULATION
Your new Atomlab 950 features a 2" x 2" Tube Assembly configuration. The Operations Manual provides
examples of geometric efficiency in Appendix A are based on a tube assembly diameter of 1.75". For the
new 2" diameter Tube Assembly, the example values provided for geometric efficiency should read as
follows:
If the wipe or calibration source is placed 1/2" from the probe, the G.E. = 27.6%
For X = 0.25", G.E. = 37.9%,
For X = 0.75", G.E. = 20.0%
NOTE: The Atomlab 950 is shipped with the Isotope Efficiency screen set to centimeters (see page 3-12 and Figure
3-10). The system can be set to centimeters, inches or any other unit of measure, as long as it is consistent for the
diameter and distance. Please verify that the set-up in the Isotope Efficiency page is set to match the 2" diameter
tube supplied with this unit.
NOTE: 2" diameter = 5.08 centimeters
1.75" diameter = 4,445 centimeters
When the Administration Mode set-up function is changed on the Isotope Efficiency page, the set-up
associated with the detector in the wipe and bioassay programs is automatically altered to match. It is
vital that you verify the correct geometric efficiency to ensure readings obtained in the wipe and bioassay
programs will be correct.
A. Geometric Efficiency (G.E.)
The value for Geometric Efficiency (G.E.) is calculated from the following equations for a well and probe:
WELL:
I.D. = Inner diameter of the well opening
X = Depth into the well, measured from the top surface
Example:
The Biodex Nal well dimensions have an I.D. = 0.75 inches and a well depth of 1.432 inches.
When the wipe (or calibration source) is placed in the well, the isotope emitting radiation will not be at
the very bottom. If we take the isotope position to be 1 inch from the top, then G.E. = 96.82%.
(For X = 1.25 inches deep, G.E. = 97.89%
For X = 0.75 inches deep, G.E. = 94.72%, which are +1.07% and -2.1% respectively, from 1 inch.)
PROBE:
O.D. = Outer diameter of the probe
X = Distance from the probe
Example:
The Biodex Nal probe O.D. = 2.00 inches. When the wipe (or calibration source) is placed .5 inch
from the probe, then G.E. = 27.64%.
For X = 0.25, G.E. = 37.9%
For X= 0.75, G.E. = 20.0%
APPENDIX A
G.E.
WELL
=
1/2
1+
1
*
100%
1+
ID
2
2X
1
2
G.E.
PROBE
=
1/2
1-
1
*
100%
1+
OD
2
2X
1
2