197381.fig.002a
(a) Background correction 30 s/frame
197381.fig.002b
(b) No background correction 30 s/frame
197381.fig.002c
(c) Background correction 120 s/frame
197381.fig.002d
(d) No background correction 120 s/frame
Figure 2: Plot of % deviation of measured activity values from true activity values with Tc-99m using the 1.4 mm pinhole apertures. Each graph represents the full range of activity values measured for all 3 microcentrifuge tubes. The negative bias at low activities introduced by background subtraction is clear in (a) and (c). This bias is eliminated for short and long frame times without any background removal, (b) and (d), respectively.