Computer Modeling of Yttrium-90–Microsphere Transport in the Hepatic Arterial Tree to Improve Clinical Outcomes

Purpose

Radioembolization (RE) via yttrium-90 (⁹⁰Y) microspheres is an effective and safe treatment for unresectable liver malignancies. However, no data are available regarding the impact of local blood flow dynamics on ⁹⁰Y-microsphere transport and distribution in the human hepatic arterial system.

Methods and Materials

A three-dimensional (3-D) computer model was developed to analyze and simulate blood-microsphere flow dynamics in the hepatic arterial system with tumor. Supplemental geometric and flow data sets from patients undergoing RE were also available to validate the accuracy of the computer simulation model. Specifically, vessel diameters, curvatures, and branching patterns, as well as blood flow velocities/pressures and microsphere characteristics (i.e., diameter and specific gravity), were measured. Three-dimensional computer-aided design software was used to create the vessel geometries. Initial trials, with 10,000 noninteracting microspheres released into the hepatic artery, used resin spheres 32-μm in diameter with a density twice that of blood.

Results

Simulations of blood flow subject to different branch-outlet pressures as well as blood-microsphere transport were successfully carried out, allowing testing of two types of microsphere release distributions in the inlet plane of the main hepatic artery. If the inlet distribution of microspheres was uniform (evenly spaced particles), a greater percentage would exit into the vessel branch feeding the tumor. Conversely, a parabolic inlet distribution of microspheres (more particles around the vessel center) showed a high percentage of microspheres exiting the branch vessel leading to the normal liver.

Conclusions

Computer simulations of both blood flow patterns and microsphere dynamics have the potential to provide valuable insight on how to optimize ⁹⁰Y-microsphere implantation into hepatic tumors while sparing normal tissue.