FIGURE 5. Relationship between HU on CT (x axis) and apparent radioactivity level (y axis) in phantoms filled with both iodinated contrast and ¹⁸F-FDG. At low HU, CT (upper 2 curves) and ⁶⁸Ge attenuation maps gave identical results. At higher HU, CT results were markedly elevated. This indicated that high levels of iodinated contrast could result in miscorrection (overcorrection) of PET data and in hot spots. Thus, contrast must be used cautiously in patients to avoid this problem. (Reprinted with permission from (13)).