Fig. 8.

SPECT sensitivity (observed primary photons count rate per activity) as a function of activity (a), photopeak count rate (b, 187–226 keV) and wide-spectrum count rate (c, 18–680 keV). The vertical coloured dotted lines indicate, for each phantom, the maximum quantifiable activity and usable photopeak count rate, which are both geometry-dependant (a and b, respectively; those of the CTDI-16 phantom could not be precisely determined due to missing points at high activity). The vertical black dotted line corresponds to the unique, geometry-independent maximum wide-spectrum count rate of the SPECT system (c; ~350 kcps). Planar data (Air-2D, averaged for both detectors) is shown for comparison