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E1556. Angiography and Tc-99m-MAA Mapping Prior to Transarterial Radioembolization with Yttrium-90 (TARE-Y90) of Liver Tumors: Exploring the “Why”
Authors
  1. Jason Kim; Brooke Army Medical Center
  2. John Pavlus; Brooke Army Medical Center
Background
Transarterial radioembolization (TARE), also referred to as selective internal radiation therapy (SIRT), is a targeted endovascular treatment for nonresectable liver tumors using radioactive yttrium-90 (Y-90) microspheres. TARE takes advantage of preferential hepatic arterial recruitment by hypervascular liver tumors by delivering high radiation dose to the tumor with relative sparing of healthy liver parenchyma. The treatment involves a two-step process consisting of a pretreatment angiographic exam with Tc-99m-MAA mapping followed by Y-90 microsphere delivery.

Educational Goals / Teaching Points
The purpose of this exhibit is to highlight the importance, principles and key findings of planning arteriography and Tc99m-MAA scintigraphy with SPECT/CT for the purpose of transarterial radioembolization with Y-90. Properties of Y-90 as well as indications and contraindications of radioembolization for liver tumors will be briefly reviewed. We will discuss the technique and essential components of the angiographic exam with a focus on variant hepatic arterial anatomy, tumor vascular anatomy, extrahepatic collateralization and arteries susceptible to nontarget embolization. Tc99m-MAA administration, calculation of the hepatopulmonary shunt, and interpretation of SPECT/CT images and will be explored. Finally, we will review how the mapping procedure influences treatment delivery through a case-based approach.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Planning arteriography for TARE involves systematic evaluation of the superior mesenteric, celiac and hepatic arteries, as well as the vessels supplying the target lesion. The intent of the procedure is to identify the optimal treatment artery that will deliver tumoricidal dose to the tumor while sparing healthy liver parenchyma and extrahepatic microsphere deposition. Potential extrahepatic sites of treatment delivery should be identified and embolized. Ideally, selection of the target artery for Tc99m-MAA infusion should closely simulate the intended target for subsequent radioembolization. Following Tc99m-MAA administration, scintigraphy with SPECT/CT is performed in the nuclear medicine department to assess for the degree of pulmonary shunting, the distribution of hepatic activity and sites of potential extrahepatic uptake. SPECT/CT may identify nontarget radiotracer activity that can be optimized or demonstrate uncorrectable uptake that precludes the patient from treatment.

Conclusion
Careful attention and understanding of mapping arteriography and Tc-99m-MAA scintigraphy are essential for delivering the right treatment dose to the right location while preventing nontarget embolization and significant complications.