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Table 3 Calibration factor and dead-time constant (± SE) derived from planar images

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

No. of acquisitions
Activity range (MBq)
Photopeak count rate range (cps)
Wide-spectrum count rate range (cps)
DetectorCalibration factor (cps/MBq)Dead-time constant (μs)
Method AMethod B
Photopeak
Method B
Wide-spectrum
Method A
Photopeak
Method B
Photopeak
Method A
Wide-spectrum
Method B
Wide-spectrum
Low activity rangeFull activity range
73019.42 ± 0.029.49 ± 0.019.44 ± 0.012.00 ± 0.012.06 ± 0.010.541 ± 0.0010.547 ± 0.002
19–40019–10,80929.35 ± 0.039.32 ± 0.019.27 ± 0.022.13 ± 0.012.10 ± 0.010.573 ± 0.0020.553 ± 0.004
208–4049208–94,8001 and 29.38 ± 0.039.40 ± 0.019.36 ± 0.012.07 ± 0.012.08 ± 0.010.557 ± 0.0020.550 ± 0.003
850–14,400850–355,034
  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 paralysable model to the data (Eq. 3). Method B refers deriving both the calibration factor and the dead-time constant through a single curve fit with 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