CIO 2021-18 Evaluating Effect of Vascularity on Micro-Embolic Performance of Y-90 Microspheres Using Novel Hepatic Tumor Model

Purpose: The purpose of this study was to investigate the impact of vascularity on radioembolic performance in a simulated liver tumor using 20-30μm diameter glass Y-89 microspheres (MS). A novel microfluidic tumor vascular model (TVM) was used to quantify characteristics of radioembolization (RE) that would otherwise be difficult to observe in vivo.

Material and Methods: The TVM represented a 3.5cm (22cc) tumor in a 1400cc liver with a total hepatic flow of 160mL/min. The inlet of the TVM branched from a diameter of 1mm to four microfluidic trees which further branched down to a total of 6400 outlet arterials. The outlet arterioles had a length of 230μm and tapered from 30μm to 18μm wide. The silicone TVM was connected to a 3D-printed hepatic vascular system consisting of a proper hepatic artery (PHA), left/right hepatic arteries (LHA/RHA), and 16 outlets each 1mm in diameter; one of which fed the TVM. The PHA was perfused with a glycerin-water mixture (3.5cP viscosity) at a pressure of 140/60mmHg and a rate of 160mL/min. A 2.9F Cook Cantata (0.027in ID) microcatheter was placed distal to the RHA origin into a 2mm caliber artery feeding the TVM and two additional arteries. MS were administered via syringe pump in a continuous 2mL injection (0.3mL/s) using a dual-syringe delivery system. The TVM flow rate was adjusted to simulate highly vascular (24mL/min, T/N = 9.6) and moderately vascular (16mL/min, T/N = 6.4) test cases. Following delivery, the TVM was disconnected from the hepatic vascular system and imaged.

Results: On average, 63 ± 10mg (mean ± standard deviation) of MS were administered, with 90 ± 8% being delivered to the tumor (rest non-target arteries) across both tests cases (N = 4 for each). For both cases, peak particle deposition was observed at a distance of 1.0mm from the arteriole outlets. For the moderately vascular case, a secondary proximal peak was observed 4.5mm from the arteriole outlets. MS penetrated a maximum distance of 179 ± 4μm into the outlet arterioles (95th percentile) for the highly vascular case. The moderately vascular case showed a significantly lower maximum penetration of 169 ± 4μm (p < 0.05).

Conclusions: These results show that the characteristics of Y-90 RE may vary significantly based on the degree of vascularity in liver tumors, with the potential for more proximal implantation and reduced maximum distal penetration in the less vascular case.