Patient 10. (a) Catheter-directed CT angiogram of the anterior branch of the right hepatic artery, supplying segments V and VIII, demonstrates contrast enhancement of a large portal vein tumor thrombus (arrow). (b, c) A 90Y PET VOI of the activity within the portal vein tumor thrombus was defined by volumetric isocontour thresholding, visually constrained to its anatomical margins as seen on the catheter-directed CT angiography. Within this VOI, the mean 90Y radioconcentration at the time of scan (5,239.8 kBq/ml) was decay-corrected back to the time of 90Y radioembolization (6,653 kBq/ml). By 90Y MIRD macrodosimetry, the mean absorbed dose of the portal vein tumor thrombus was approximately 316 Gy within the VOI. (d) Follow-up triphasic CT of the liver in the arterial phase at 4 months post-radioembolization demonstrates a complete lack of contrast enhancement within the VOI (arrow), suggesting a complete response and clinically validates the 90Y PET quantification.