Intraarterial Hepatic SPECT/CT Imaging Using 99mTc-Macroaggregated Albumin in Preparation for Radioembolization

Current standard practice for radioembolization treatment planning makes use of nuclear medicine imaging (NMI) of Tc-99m-macroaggregated albumin (Tc-99m-MAA) arterial distributions for the assessment of lung shunting and extrahepatic uptake. Our aim was to retrospectively compare NMI with mapping angiography in the detection and localization of extrahepatic Tc-99m-MAA and to evaluate the typical and atypical findings of NMI in association with catheter placement. Methods: One hundred seventy-four patients underwent diagnostic angiography in preparation for radioembolization. Tc-99m-MAA was administered to the liver via a microcatheter positioned in the desired hepatic artery. Planar scintigraphy imaging followed by SPECT/CT imaging was obtained within 2 h. All images were reviewed for hepatic and extrahepatic Tc-99m-MAA deposition and compared with the mapping angiogram. Results: Intrahepatic lobe shunting was present on NMI in only 2.9% of the cases but was present in 62.5% of the patients with portal vein thrombosis. Extrahepatic distributions included lungs (100%), the gallbladder (49%) if present, and locations involving hepaticoenteric arterial anatomy recognized on angiograms (16%). Free pertechnetate was identified on 38% of the nuclear medicine images. Three percent of nuclear medicine images showed alternative findings such as a thyroid nodule or metallic artifact. Conclusion: Patients being considered for radioembolization should undergo both angiography and scintigraphy for the assessment of hepaticoenteric arterial anatomy, hepatopulmonary shunting, and appropriate dosimetry considerations. Knowledge of the expected distribution of Tc-99m-MAA with normal variants and potential nontarget delivery to adjacent structures is critical in improving clinical outcomes.