The required number of emitted photons/voxel to obtain a stable reconstruction was estimated by the coefficient of variation (CV) for the different numbers in a 22-mm background sphere in the phantom, using ten subsets and six iterations.
Whereas journalists equate ideology with the clash of programs and parties in the debate sphere, academics know that the consensus or background sphere is almost pure ideology: the American creed.
The contrast recovery coefficients obtained with a sphere phantom would depend on sphere and background activities, sphere to background contrasts, and the number of total acquired counts [23].
An abdominal-shaped container (31 × 23 crossrosectionion × 8 cm length, 4.51 volume, Figure 1) was filled with 350 MBq of90Y (background + spheres).
This phantom needs to be filled with 2.0 and 20.0 kBq FDG/mL in the background and spheres, respectively.
Figure 5 shows the count rate of prompt, delayed, and true coincidences for the total activity (including background and spheres).
Therefore, the activity concentration levels in the background and spheres for further evaluation were set at 18 and 54 kBq/cc, resulting in mean activity concentration of the entire phantom of approximately 18.3 kBq/cc.
In order to simulate clinical Tc-99m SPECT/CT scans, the activity concentration levels in the background and spheres in the NEMA body phantom were set at 18 and 54 kBq/cc, respectively (Fig. 1).
Eight images were captured, each with a different ratio of the specific activity between the phantom background and the spheres and also different acquisition time.
The value of BG was determined from three ROIs drawn in the background, between the spheres and the edge of the phantom.
Quantitative accuracy was assessed through measures of total phantom activity, activity concentration in background and hot spheres, misplaced counts in a nonradioactive insert, and background variability.
