Hepatic arterial perfusion scintigraphy with Tc-99m-MAA and SPECT-CT in planning selective internal radiation therapy with Yttrium-90 microspheres in the management of unresectable liver tumors

Abstract

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Learning Objectives: 1. Understand the technique and role of hepatic arterial perfusion scintigraphy with Tc-99m-MAA in the planning of SIRT for unresectable liver tumors. 2. Provide examples of imaging findings (expected patterns, normal variants and abnormal patterns) and their implications on SIRT. 3. Discuss the advantages and pitfalls of SPECT-CT compared to planar and SPECT-only imaging in this application.

Abstract Body: Selective internal radiation therapy (SIRT) is a relatively new therapeutic modality for the management of unresectable liver tumors. It involves the intraarterial delivery of a high dose of beta radiation via Yttrium-90 microspheres injected directly into the hepatic artery branch supplying the tumor. This targeted therapy delivers a much higher radiation dose to the tumor than would be possible with conventional radiotherapy. In order to deliver the maximum safe dose of Y-90 while preventing radiation damage to the lungs or GI tract, pre-treatment mapping of perfusion pattern is necessary to assess abdominal and pulmonary shunting. Tc-99m MAA has a particle size similar to Y-90 microspheres and thus can be used to simulate Y-90 microsphere distribution during SIRT. Potential shunting to the lungs is quantified for appropriate therapy dose calculation. Significant shunting to the GI tract may be a contraindication of SIRT, unless the culprit vessel is identified and embolized first or otherwise avoided. The technique will be described and examples of normal and abnormal imaging patterns will be presented. We believe SPECT/CT has advantages compared to planar or SPECT-alone imaging.