FIGURE 4. ¹⁸F-FDG (left), WBC (middle), and marrow (right) images. (A) On ¹⁸F-FDG image, there is BPI activity along tibial component (arrowheads) of infected 4-mo-old cemented left total knee replacement. Both components were loose. Target-to-background ratio was 5.2. WBC/marrow study is positive for infection. (B) On ¹⁸F-FDG image, BPI activity, less intense than that in A, is present around aseptically loosened tibial component (arrowheads) of 8-y-old cemented right total knee replacement. Femoral component was fixed. Target-to-background ratio was 3.7. WBC/marrow study, in which there is spatially congruent distribution of 2 tracers, is negative for infection.