FAP and neoplasm: Notably, [99mTc][Tc-(CN-PEG4-FAPI)6]+ exhibited sixfold higher tumor uptake (8.05 ± 1.48% ID/g) then [99mTc][Tc-(CN-C5-FAPI)6]+ (1.34 ± 0.13% ID/g) at 1h post-injection and a superior tumor/nontarget ratio, indicating its potential as a promising candidate for tumor imaging targeting FAP.