Characteristics of catheter injection for predictive particle transport modeling in Y-90 transarterial radioembolization procedures*

Hepatic cellular carcinoma is one of the most common forms of liver cancer. Depending on the cancer's progression, treatment can include a combination of external radiation therapy, chemotherapy, or surgery. Radioembolization using microspheres loaded with a radioactive isotope such as yttrium-90 (Y-90) has shown promise increasing patient outcomes but requires personalized and complex planning due to sensitivity of liver tissue to radiation and the need to reach a certain threshold of radiation dose in the tumors. Our modeling framework, CFDose, incorporates clinical patient cone-beam Computed Tomography images to predict microsphere transport in the patient liver vasculature using computational fluid dynamics (CFD). For this work, we consider a finite-thickness catheter wall at injection points that are at least one generation downstream of either the left or right hepatic arteries (considered a super selective injection). These considerations are important when super selective injections are used since the catheter obstructs the vessel lumen significantly. We also consider the effects of the local injection curvature on the injection profile by considering increasing levels of tortuosity. The model geometry we employ is an idealized structure where the surface mesh is truncated following two bifurcations from the right hepatic arteries. Preliminary results indicate increased particle asymmetries downstream of a tortuous injection segment when compared to an idealized extrusion or considering only an idealized parabolic flow profile. The injection location geometries are motivated by a particular patient case where the microsphere injection occurred directly downstream of a curved vascular segment, requiring a second injection further downstream the hepatic arterial tree. In such cases, we recommend carefully considering the segment tortuosity on modeling Y-90 injection.