(A) Mechanism of uptake of 18F-ARAG: Reproduced from Levi J et al. CCR (doi:10.1158/0008-5472.CAN-19-0267). (B) Patient with head and neck carcinoma. PET/CT imaging with 18F-FDG and 18F-ARAG shows prominent uptake in the lesions in larynx; uptake is also noted in 18F-ARAG scan with heterogenous uptake. (Courtesy: Drs. Colevas, Sunwoo, and Davidzon, Stanford University) (Reprinted with permission from Elsevier, Pandit-Taskar N, Postow MA. Immune-Directed Molecular Imaging Biomarkers. Semin Nucl Med. 2020 Nov;50(6):584-603. doi: 10.1053/j.semnuclmed.2020.06.005. Epub 2020 Jul 15. PMID: 33059826.)