FIGURE 2. On ¹⁸F-FDG image (left), there is focal activity at distal tip of aseptically loosened femoral component (arrowhead) of 5-y-old left cemented total hip replacement. Similar focus is present on marrow image (right; arrowhead), indicating that activity on ¹⁸F-FDG image is due to marrow accumulation of tracer, not to infection. In at least some cases, periprosthetic activity on ¹⁸F-FDG images is due to marrow uptake of tracer.