Native anti-PD-L1 IgG antibody (89Zr-DFO-C4) was compared with a neonatal Fc receptor (FcRn) low-affinity mutant (89Zr-DFO-C4Fc-MUT) in a murine syngeneic glioblastoma model.15 Transcranial focused ultrasound was applied before antibody injection to disrupt the blood–brain and blood–tumor barrier and facilitate antibody entry into the brain. Here, FCGRT is linked to glioblastoma.