Intra-Arterial CT Angiography Visualization of Arterial Supply to Inferior Vena Cava Tumor Thrombus Prior to Radioembolization of Hepatocellular Carcinoma
A 51 year old Chinese man with a 20-year history of hepatitis B presented with epigastric pain. A contrast enhanced CT study at an outside institution revealed a large right hepatoma with right portal vein thrombosis and direct extension of the tumor into the intra-hepatic IVC []. In view of its size and vascular involvement, the patient was not suitable for systemic therapy or trans-arterial chemoembolization (TACE). He was then referred to us for suitability of Y90 radioembolization.\nPre-treatment planning was performed by obtaining a hepatic angiography using a hybrid 16-slice CT/angiography system (Toshiba Medical Systems, Tokyo, Japan) and a Technetium-99m macro aggregated albumin (Tc-99m MAA) scan. The conventional digital subtraction angiography revealed a replaced right hepatic artery from the superior mesenteric artery. The replaced right hepatic artery, middle hepatic artery, and the right inferior phrenic artery were superselectively accessed using a 2.7F Progreat microcatheter (Terumo, Tokyo, Japan) inserted coaxially via a 4F Sim-1 catheter (Cordis, Miami, FL). Conventional DSA and intra-arterial CT angiography (IACTA) were performed for all three arteries. Arterio-portal shunting limited to the right lobe was seen during DSA of the replaced right hepatic artery and right inferior phrenic artery [Figures and ]. The bulk of the tumor was supplied mainly by the right and middle hepatic arteries. There was also a smaller contribution from the right inferior phrenic artery supplying the superior aspect of the tumor and the IVC tumor thrombus []. Tc-99m MAA (total of 5 mCi in 3 ml) was injected first in equal proportions into the replaced right hepatic artery, followed by the middle hepatic artery and subsequently the right inferior phrenic artery. Immediate planar and single-photon emission computed tomography (SPECT) CT images showed satisfactory tumor to normal liver ratios in the replaced right and middle hepatic artery territories. However, there was poor particulated uptake in the inferior phrenic arterial territory with no significant tracer uptake in the IVC tumor thrombus []. The liver-lung shunting ratios at 8.7% were within normal acceptable limits.\nIn view of the findings, the patient was deemed suitable for radioembolization 2 weeks later. The right inferior phrenic artery was bland embolized using 355-500 micron Contour polyvinyl alcohol particles (Boston Scientific/Target Vascular, Freemont, CA), so as to allow intra-tumor re-distribution of arterial supply from the hepatic arteries. After vascular stasis was obtained in the right inferior phrenic artery from particle embolization, the middle hepatic artery was targeted. Unfortunately, attempts at accessing the middle hepatic artery resulted in spasm requiring intra-arterial glyceryl trinitrate (GTN) infusion. Following this, 0.5 GBq of Y90 microspheres (Sirtex Medical, Lane Cove, Australia) was infused into this artery as there was good forward flow following GTN infusion. Although it was planned for Y90 to be delivered into the replaced right hepatic artery, pre-injection DSA demonstrated significant changes in flow dynamics. There was interval development of extensive arterio-portal shunting into the left liver lobe, which was not seen at the initial planning angiogram []. It was deemed unsafe to proceed with Y90 injection in view of significant dose to the normal liver parenchyma of the left lobe. Immediate Bremsstrahlung study showed localization of Y90 microspheres in a small portion of the right lobe tumor, and small amount of activity in the extra-tumoral hepatic parenchyma from the arterio-portal shunting.\nAs the planned administration of Y90 microspheres into the replaced right hepatic artery did not occur, the patient did not response to treatment from solitary administration into the middle hepatic artery. Serial follow-up CT studies showed increasing tumor burden and development of pulmonary metastases. The patient finally succumbed to his disease 7 months after radioembolization.