Patient 12. (a, b) Portal vein tumor thrombosis (arrow) in a multifocal HCC seen on portal venous phase of a triphasic CT liver. (c)90Y PET/CT demonstrates absent activity within the portal vein tumor thrombus. (d) The diffuse nature of 90Y bremsstrahlung SPECT/CT is unable to resolve the absence of activity within the portal vein tumor thrombus. (e, f) Four months post-radioembolization, a follow-up triphasic CT liver in the portal venous phase shows significant progression of portal vein tumor thrombosis, validating the 90Y PET/CT findings.