FOLH1 and neoplasm: Both heterodimeric tracers showed higher tumor uptake in A549-FAP and 22Rv1 tumor-bearing mice compared to the corresponding monomeric tracers (6.40 ± 0.32 %ID/g for [18F]AlF-PSMA-FAPI-01 and 6.47 ± 0.76 %ID/g [18F]AlF-PSMA-FAPI-02 vs. 5.25 ± 0.27 %ID/g for [18F]FAPI-42 in A549-FAP tumors, p < 0.05; 12.37 ± 0.40 %ID/g for [18F]AlF-PSMA-FAPI-01 and 12.85 ± 2.43 %ID/g for [18F]AlF-PSMA-FAPI-02 vs. 6.44 ± 1.78 %ID/g for [18F]PSMA-BCH in 22Rv1 tumors, p < 0.05) (Figure 5A and Supplemental Table S2).