Inclusion Criteria:  Age 18 years or older (no upper limit of age) Hepatocellular carcinoma diagnosis made histologically or radiographically in accordance to National Comprehensive Cancer Network guidelines (3.2019 version or higher) Barcelona Clinic Liver Cancer Stage B or C Has measurable disease defined as at least one tumor lesion that can be accurately measured according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 on CT/MRI completed within past 6 weeks of eligibility screening Under the care of a licensed medical oncologist Life expectancy > 6 months Deemed eligible for treatment with an immune checkpoint inhibitor agent based on the treating medical oncologist's assessment of previous treatment failure, clinical/performance/virology status, and liver/renal/hematologic function. Child-Pugh score of 7 or less Creatinine clearance ≥ 40 mL/min, measured or calculated using the Cockcroft-Gault formula ALT and AST ≤5x upper limit of normal Total bilirubin ≤3 mg/dL Albumin ≥2.8 g/dL  Exclusion Criteria:  Weight > 500 lbs (PET/CT limit) Pregnant or lactating female (those of child-bearing potential must be re-screened within 7 days prior to PET/CT imaging) Serious underlying medical condition that would impair patient's ability to tolerate the imaging procedure Concurrent treatment with a non-targeted therapeutic agent. Concurrent enrollment in an ICI-treatment trial and combination ICI treatment are allowed.