Segmental Perfusion Differences on Paired Tc-99m Macroaggregated Albumin (MAA) Hepatic Perfusion Imaging and Yttrium-90 (Y-90) Bremsstrahlung Imaging Studies in SIR-Sphere Radioembolization: Associations with Angiography

Abstract

Surgically unresectable primary and metastatic liver tumors have been increasingly treated with Y-90 radioembolization. In preparation for Y-90 radioembolization therapy, a baseline angiogram and a Tc-99m MAA hepatic perfusion study simulating Y-90 microsphere infusion are routinely performed, followed by a 2nd angiogram in which the catheter is positioned in the same position as during the baseline angiography. However, radiotracer distribution on paired Tc-99m MAA hepatic perfusion imaging and post-therapy Y-90 bremsstrahlung imaging studies does not always match. The purpose of this study was to examine perfusion differences or mismatch which involve hepatic segment(s) and to identify underlying causes by correlating with angiography. 81 paired Tc-99m MAA hepatic perfusion imaging and post-therapy Y-90 bremsstrahlung imaging studies and corresponding angiograms were reviewed. 31 studies showed segmental perfusion differences (SPDs). SPDs were less frequently observed with infusion into the left hepatic artery (LHA) as compared to the proper (PHA) and right hepatic artery (RHA) (P<0.05). Significant associations were found with differences in catheter tip position between the two angiograms (P<0.001), catheter tip in proximity to an arterial bifurcation (P<0.01) or a small branch (P<0.01). Differences in catheter position, in combination with proximity to an arterial bifurcation or an arterial branch showed strong association with SPDs (P<0.001). In conclusion, when the catheter tip is in proximity to an arterial bifurcation or a branch, subtle differences in its position can alter microsphere perfusion or trajectory to the target vessels, which can be demonstrated by segmental perfusion mismatch on paired Tc-99m MAA hepatic perfusion imaging and posttherapy Y-90 bremsstrahlung imaging studies.