Fig. 2

Phantom images with different acquisition times created to determine the optimal acquisition time as a reference: a 840 s (200% dose), b 630 s (150% dose), c 420 s (100% dose), d 315 s (75% dose), e 210 s (50% dose), f 105 s (25% dose), g 52 s (12.5%), and h 26 s (6.25% dose). The numbers represent the acquisition time. Percentages in parentheses indicate the percentage of a 420-s acquisition (surrounded by a rectangle) as 100%