Fig. 6

a Display of three sets of data (decay corrected counts/second), from detector heads 1 and 2 using two ⁵⁷Co flood phantoms stacked in two different orientations during the DQA. The DQA was performed with each stacking orientation for that particular morning of data acquisition (both scans acquired on the same morning—days 1, 5, and 8). Note Y-axis does not start at zero. b Similar to Fig. 6a, b displays one set of data (counts/second), from detector heads 1 and 2 using two ⁵⁷Co flood phantoms stacked in two different orientations during the DQA, but with detector head moved slightly away from the flood phantom. The DQA was performed with each stacking orientation for that particular morning of data acquisition (day 1 both scans were acquired). Note Y-axis does not start at zero