Regarding the currently most frequently used ligands ([68 Ga]Ga-PSMA-11, [18F]DCFPyL, 18F-PSMA-1007, 18F-rhPSMA-7.3, [99mTc]Tc-PSMA-I&S, [99mTc]Tc-MIP1404), various groups reported that tumor-to-salivary gland or tumor-to-liver ratios can serve as scanner-independent surrogate criteria [96], but in exchange the confounder “reference-organ variability” becomes an issue. The gene discussed is FOLH1; the disease is neoplasm.