A Hybrid Particle-Flow CFD Modeling Approach in Truncated Hepatic Arterial Trees for Liver Radioembolization: A Patient-specific Case Study

Abstract

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer. At its intermediate, unresectable stage, HCC is typically treated by local injection of embolizing microspheres in the hepatic arteries to selectively damage tumor tissue. Interestingly, computational fluid dynamics (CFD) has been applied increasingly to elucidate the impact of clinically variable parameters, such as injection location, on the downstream particle distribution. This study aims to reduce the computational cost of such CFD approaches by introducing a novel truncation algorithm to simplify hepatic arterial trees, and a hybrid particle-flow modeling approach which only models particles in the first few bifurcations. A patient-specific hepatic arterial geometry was pruned at three different levels, resulting in three trees: Geometry 1 (48 outlets), Geometry 2 (38 outlets), and Geometry 3 (17 outlets). In each geometry, 1 planar injection and 3 catheter injections (each with different tip locations) were performed. For the truncated geometries, it was assumed that, downstream of the truncated outlets, particles distributed themselves proportional to the blood flow. This allowed to compare the particle distribution in all 48 “outlets” for each geometry. For the planar injections, the median difference in outlet-specific particle distribution between Geometry 1 and 3 was 0.21%; while the median difference between outlet-specific flow and particle distribution in Geometry 1 was 0.40%. Comparing catheter injections, the maximum median difference in particle distribution between Geometry 1 and 3 was 0.24%, while the maximum median difference between particle and flow distribution was 0.62%. The results suggest that the hepatic arterial tree might be reliably truncated to estimate the particle distribution in the full-complexity tree. In the resulting hybrid particle-flow model, explicit particle modeling was only deemed necessary in the first few bifurcations of the arterial tree. Interestingly, using flow distribution as a surrogate for particle distribution in the entire tree was considerably less accurate than using the hybrid model, although the difference was much higher for catheter injections than for planar injections. Future work should focus on replicating and experimentally validating these results in more patient-specific geometries.

Transarterial radioembolization: a systematic review on gaining control over the parameters that influence microsphere distribution

“…Bomberna et al. ( 2022 ) also investigated the effect of truncating the geometry to reduce computational effort. They found that modeling only the larger branches and assuming particles follow flow distributions in some of the smaller branches could lead to up to 27% less computational effort while outlet-specific differences in particle distributions deviated at most 3.5%.…”

“…(Lertxundi et al., 2021 ) and Bomberna et al. ( 2022 ) showed that judicious removal of certain parts of the geometry has only a small effect on the simulated microsphere distributions. This supports CFD as a relevant tool in the clinic, where the large computational resources required for detailed simulations are often unavailable.…”

In silico modeling for the hepatic circulation and transport: From the liver organ to lobules

“…In recent years, 3D computational fluid dynamics simulations have been made for liver radioembolization, which makes use of catheters to deploy radiation‐emitting microspheres to desired locations in the hepatic artery network (Aramburu et al, 2019, 2020; Bomberna et al, 2022; Taebi et al, 2020). Important parameters such as the size, injection velocity of microspheres, and the location of catheter tip were investigated (Aramburu et al, 2020).…”

“…F I G U R E 2 Computational models for hepatic flow: (a) a 0D model for a rat liver lobe (Debbaut, De Wilde, et al, 2012); (b) a 0D model consists of three pi-filters for modeling the HABR in human liver (Ho, Sorrell, Bartlett, & Hunter, 2013); (c) a hybrid 0D-1D model for simulating flow variations after hepatectomy on pig livers ; (d) a 1D model for a subject-specific portal system (Ho et al, 2011); (e) a 3D model for comparing the streamlines in portal veins between healthy subjects and cirrhotic patients (George et al, 2015) In recent years, 3D computational fluid dynamics simulations have been made for liver radioembolization, which makes use of catheters to deploy radiation-emitting microspheres to desired locations in the hepatic artery network (Aramburu et al, 2019(Aramburu et al, , 2020Bomberna et al, 2022;Taebi et al, 2020). Important parameters such as the size, injection velocity of microspheres, and the location of catheter tip were investigated (Aramburu et al, 2020).…”

“…In silico models are valuable in revealing particle-flow dynamics associated with the design of catheters, and patient-specific dosing schemes. To that end, various numerical techniques such as outflow boundary conditions (Taebi et al, 2020), and artery tree truncation schemes (Bomberna et al, 2022), have been experimented.…”