CAPINTEC, INC. CAPTUS
®
600
Input the desired Counting Period; the maximum accepted value is 999 seconds, and the
minimum accepted value is 1 second.
X-RAY/GAMMA RATIO
These factors are necessary because the I125 X-Ray peak overlaps with the I131 X-Ray
peak and the I123 X-Ray peak. The CAPTUS
®
600
calculates I125 activity in Bioassay by
first searching for the I131 peak at 364 keV. If the I131 peak is detected, the contribution
from the I131 X-ray (counts in the I131 gamma peak times the I131 X-Ray gamma ratio) is
subtracted from the I125 X-Ray region of interest. It then searches for the I123 peak at
159keV. If the I123 peak is detected, the contribution from the I123 X-Ray (counts in the I123
gamma peak times the I123 X-Ray gamma ratio) is subtracted from the I125 X-Ray region of
interest. The default values are 8.5% for I131 and 92% for I123 and have been derived from
actual test data.
The last field is the DISTANCE, in centimeters, between the Probe and the neck. This must
be set to the same distance used in calculating Conversion Factors for the Probe for I125,
I123 and I131.
When all information is correct, press the F4 [OK] key.
Note: In order to report the Bioassay in units of activity rather than in counts, the CAPTUS
®
600
must have Conversion Factors for I125, I123 and I131 in the Probe in memory.
Reference CHAPTER5: SYSTEM INITIALIZATION, SECTION CONVERSION
FACTORS.
The Bioassay Setup menu (Figure 17-3) will re-appear.
Note: It is possible to perform a Bioassay without associated staff data. The results of such
a test will not be stored.
MAKING BIOASSAY MEASUREMENTS
In the Main Probe Screen, press the F4 [BIO] key. The Bioassay Initials Screen (Figure 17-
8
) will appear:
November 07 STAFF BIOASSAY 17-5
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