Non-invasive methods for quantifying [(18)F]FDG uptake in tumours often require normalization to either body weight or body surface area (BSA), as a surrogate for [(18)F]FDG distribution volume (DV). Whereas three dimensions are involved in DV and weight (assuming that weight is proportional to volume), only two dimensions are obviously involved in BSA. However, a fractal geometry interpretation, related to an allometric scaling, suggests that the so-called 'body surface area' may stand for DV.