THYROID UPTAKE 4-6
Maximum Count Time
All of the following examples had a 60 sec maximum count time set in the Uptake SETUP loop. The first
example did not require longer than 60 seconds on each measurement to satisfy the 98% accuracy
requirement. The next two examples did require a longer than 60 seconds on each measurement to satisfy
the 98% accuracy requirement. The next two examples did require a longer than 60 seconds on some of
the measurements but the actual time was limited to 60 seconds automatically. The uncertainty resulting
from such a shortened time is stated with the example.
Minimum Count Time
The minimum count time for any count in the uptake mode is 10 seconds. This is illustrated in all three
examples during the lab background count.
EXAMPLE 1: I-123, 6 HOUR UPTAKE, 98%, 60 SEC MAX COUNT TIME
Comment
The automatic time selection controlled the counting since all times were less than the maximum set
count time of 60 sec. The patient was required to remain in a counting position for only 29 seconds for the
thyroid and 12 seconds for the background count. This is very beneficial for hyperthyroid and elderly
patients. Plus the auto-count time mode takes less time to set up. The Uptake of 25.5% has a 2%
uncertainty meaning it could be 25.1% to 26.1%.
NOTE: In this example, and the following two, the “pill” was counted at the time of administration (Measured
Standard) and the count rate was decayed to the time of the thyroid count (value in parenthesis).
EXAMPLE 2: I-123, 6 HOUR UPTAKE, 98%, 60 SEC MAX COUNT TIME
CONTENTS
Measured Standard
Measured Lab Bkgnd
Decayed Standard
Measured Thyroid
Measured Pat. Bkgnd
538,920
64
(393468)
108,060
7,500
53 sec
10 sec
29 sec
12 sec
53 sec
2.2 sec
29 sec
12 sec
Uptake = 25.5% 2% (25.1% to 26.1%)
cpm
Actual Count
Time
Computed Auto
Time
+
-
Measured Standard
Measured Lab Bkgnd
Decayed Standard
Measured Thyroid
Measured Pat. Bkgnd
538,920
64
(393468)
36,000
12,000
53 sec
10 sec
60 sec
60 sec
53 sec
2.2 sec
119 sec
81 sec
Uptake = 6.1% 2.3% (5.96% to 6.24%)
cpm
Actual Count
Time
Computed Auto
Time
+
-
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