Figure 4.

Normalized image intensity profiles through images of the contrast phantom (Fig. 1) demonstrating hot-to-cold image contrast and how the background obtained with ¹²⁴I differs in shape and level from that with ¹⁸F. Profile windows (six transaxial slices wide) were placed in a coronal slice through the cold insert, and a mean profile was computed. The resulting profiles were normalized to a common maximum and plotted for comparison. (A) Semilog plot. (B) Linear plot.