Fig. 4

The illustration indicates volumes for which accumulation of ²¹²Pb could be visualised and distinguished. It shows how visualisation depends on several factors, here factors volume, acquisition time, and activity concentration are plotted. Many more factors affect which volumes are seen in images, for instance acquisition and reconstruction settings and surrounding volumes with uptake. What is visible in an image is of course objective, but the figure serves to indicate what was found in this study. The mouse symbols indicate volumes seen in the mice, for instance the two yellow mice with the largest volumes represent the liver uptakes of the mice 24 h post-injection. Uptake could be seen with optimised windowing, but they were not clearly distinguishable volumes. The four green mice represent the uptake in tumours after 24 h, all of which were clearly distinguishable. The other symbol represents volumes in the mouse phantom. Only the high-activity concentration regions at the first imaging time point were clearly visible and distinguishable, but some low-activity regions, the heart and liver, could be vaguely made out with optimised settings. The schematic mouse in the figure was provided by Servier Medical Art (https://smart.servier.com/) and the schematic phantom was adapted with permission from a schematic from Bioemtech