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Table 4 Calibration factor and dead-time constant (± SE) derived from SPECT data

From: Comprehensive SPECT/CT system characterization and calibration for 177Lu quantitative SPECT (QSPECT) with dead-time correction

PhantomLow activityFull activity rangeCalibration factor (cps/MBq)Dead-time constant (μs)
No. of acquisitions
Activity range (MBq)
Photopeak count rate range (cps)
Wide-spectrum count rate range (cps)
Method AMethod B
Photopeak
Method B
Wide-spectrum
Method A
Photopeak
Method B
Photopeak
Method A
Wide-spectrum
Method B
Wide-spectrum
Air-3D7
32-330
327-3154
1342-11,975
27
32-10,704
327-88,762
1342-347,060
9.62 ± 0.049.70 ± 0.039.67 ± 0.032.07 ± 0.012.15 ± 0.030.531 ± 0.0030.544 ± 0.008
CTDI-104
126-510
800-3423
5229-20,267
19
13-9646
93-60,750
665-354,256
9.91 ± 0.069.72 ± 0.039.70 ± 0.033.18 ± 0.022.93 ± 0.040.546 ± 0.0050.499 ± 0.008
CTDI-165
157-634
693-3302
5523-22,333
16
16-80,94
83-41,651
694-264,231
9.98 ± 0.099.84 ± 0.059.85 ± 0.063.77 ± 0.063.28 ± 0.120.603 ± 0.0100.528 ± 0.024
CTDI-324
293-1404
522-2364
5226-23,734
20
21-13,708
50-53,746
513-339,364
10.66 ± 0.0910.19 ± 0.0510.23 ± 0.044.47 ± 0.083.71 ± 0.070.705 ± 0.0110.594 ± 0.012
Jaszczak5
120-526
624-2335
4972-17,052
26
44-12,480
307-49,376
2650-348,334
9.50 ± 0.059.40 ± 0.059.46 ± 0.044.07 ± 0.044.04 ± 0.090.572 ± 0.0050.565 ± 0.010
  1. Method A refers to obtaining the calibration factor at low activity, i.e. a subset of the full activity range (Eq. 1), then obtaining the dead-time constant over the full activity range by fitting the data to the paralysable model (Eq. 3). Method B refers deriving both the calibration factor and the dead-time constant through a single curve fit using data from the full activity range (Eq. 3). The acquisition count rate from either the photopeak or the wide spectrum (6W, 18680 keV, Table 2) was considered for dead-time constant determination