Fig. 5From: Comprehensive SPECT/CT system characterization and calibration for 177Lu quantitative SPECT (QSPECT) with dead-time correctionObserved primary photons count rate vs. activity for planar acquisitions. The calibration factor (CF) was obtained by linear fit forced through origin of low-activity data, i.e. a subset of the full activity range (grey zone, where dead time is less than 1%) as per Method A. Data is shown for each detector separately, and averagedBack to article page