Figure 3.

Positron emission tomography (PET) activity concentration response for ¹⁸F and ¹²⁴I, using ordered subsets expectation maximum and maximum a posteriori reconstruction methods. The plot shows image-derived versus true activity concentration from PET scans of the linearity phantom filled with activity concentrations spanning the range of tissue-activity concentrations seen in the mouse antibody scans. Broken lines represent least-squares linear fits; equations and parameter standard deviations for the regression lines are shown on the right. For each syringe, a volume of interest (VOI) was created that contained the four hottest adjacent voxels in each of 25–40 slices. The average voxel value within each VOI was multiplied with the cylindrical phantom-based calibration factor appropriate to the radionuclide and reconstruction algorithm, and the resulting image-derived activity concentrations were plotted versus the measured values.