Figure 3.

Relationships of PET imaging and histological tumor properties. In brain metastases, ¹⁸F-FET uptake imaged by PET (measured as mean tumor-to-background ratio (TBR_mean) of the target volume) increased with tumor content (a; r_s = 0.3, p = 0.045) and decreased with necrosis content (b; r_s = −0.4, p = 0.014). B-lymphocyte infiltration (measured by CD20 positivity) increased with tumor content (c; r_s = 0.5, p = 0.002) and necrosis content increased with proliferation (d; r_s = 0.5, p = 0.002). Note that while scatterplots and linear regression lines are shown to illustrate the data, correlations were analyzed using Spearman’s rank correlation coefficient r_s, as tumor content, necrosis content, and CD20 positivity were not normally distributed.