Impact of catheter angle on microsphere distribution in transarterial radioembolization: an in silico study based on ex vivo porcine liver data.

Computational fluid dynamics (CFD) simulations were conducted to explore the impact of catheter angle on microsphere distribution in transarterial radioembolization (TARE). The models were designed to closely replicate conditions from previously conducted ex vivo machine-perfused porcine liver experiments and therefore improve the perspective on microsphere distribution patterns. TARE with holmium-loaded microspheres was performed on an ex vivo machine-perfused porcine liver. Catheter position was imaged using angiography and ultrasound, the hepatic arterial vasculature using 3D cone beam CT, and lobe-specific microsphere distributions using holmium-sensitive T2*-weighted MRI scans. An in-house CFD model based on lattice Boltzmann and discrete element methods was developed. Simulations were parameterized with ex vivo porcine liver geometry and flow conditions as input. To further explore the role of catheter angles beyond experimental findings, four catheter angles (0°, 15°, 30°, and 45°), gradually directed toward the hepatic arterial wall, were evaluated using CFD. Ex vivo ultrasound imaging showed that the catheter was oriented at an angle of 25.2° toward the hepatic arterial wall. The simulations revealed that catheter angle strongly influences microsphere distribution, particularly in the branches closest to the injection position (lobe 3-5). The correlation between ex vivo and simulated microsphere distributions increased with catheter angle: from poor at 0° (r = 0.123), to moderate at 15° (r = 0.511), to very strong at 30° and 45° (r = 0.809 and r = 0.807, respectively). A catheter angle directed toward the hepatic arterial wall can affect microsphere distribution. In current clinical practice, the radial catheter position is not routinely visualized, complicating the reproducibility of catheter tip positioning between scout and therapeutic doses. Future research could focus on improved catheter tip visualization and the development of more stable catheter designs to enhance the reproducibility and efficacy of TARE.