FAP and glioblastoma: More than a decade later, Pandya et al. took advantage of the nuclear decay properties of zirconium-89 (89Zr: t1⁄2 = 78.4 h, β+: 22.8%, Eβ+max = 901 keV; EC: 77%, Eγ = 909 keV) PET and Cerenkov Luminescence Imaging (CLI) to examine FAP expression in a murine model of glioblastoma multiforme (GBM), since it was previously reported that GBM tumors expressed FAP and its expression increased as tumor aggressiveness increased (Busek, et al. 2016a, b; Pandya, et al. 2020a).