###### Abstract  
Superselective intra-arterial chemotherapy (SSIAC) for oral cancer can deliver a higher concentration of anticancer agent into a tumor-feeding artery than intravenous systemic chemotherapy. However, the agent distribution between the lingual artery and facial artery (FA) is not clear in SSIAC for patients with the linguofacial trunk. The agent distribution in the SSIAC method was investigated using computational fluid dynamics (CFD). Ten three-dimensional vessel models were created from CT images of two patients with oral cancer (patients A and B) with the linguofacial trunk. Catheter models were combined with vessel models to mimic intra-arterial infusion, and the agent flow was analyzed. In patient A models, the agent distribution varied depending on the catheter tip position in the linguofacial trunk, while all anticancer agents flowed into the FA only in patient B models. This study revealed that the behavior of the agent in the common trunk is determined by the blood flow field which depends on the topography of the vessels in each patient. Therefore, the catheter tip position should be changed according to the vessel topography to deliver anticancer agents into the tumor-feeding artery. Moreover, CFD can be a useful method to predict the agent flow for each patient before SSIAC. common trunk; computational fluid dynamics; intra-arterial chemotherapy; linguofacial trunk; oral cancer 20202022 October 22 October 2020202 October 22 October  
(ICA). Furthermore, a catheter is placed into the tumor-feeding artery, which provides concurrent radiotherapy to patients [6]. There are some limitations in SSIAC due to the complexity of the catheter placement procedure. SSIAC requires a skilled technique, and the difficulty of insertion into the targeted tumor-feeding artery depends on the anatomical topography of the ECA and its branches in each patient. For instance, the lingual artery (LA) and facial artery (FA), which the main arteries that feed oral cancer, arise from the ECA with a common trunk. The incidence rates of the linguofacial and thyrolingual trunks are 2.7-31% [7; 8; 9] and 0.7-3% [7; 8; 9; 10], respectively. The mechanism of the distribution of the amount of agent among the branches that arise from the common trunk has not been fully understood (Figure 1b), although SSIAC can deliver a high drug concentration as long as the catheter tip is located in the tumor-feeding artery that arises directly from the ECA [5]. In addition to the topological feature of the artery, spasm of vessels [11] caused by inappropriate procedures could make catheter placement more difficult. In cases with difficulty in catheter insertion into the tumor-feeding arteries, a linear catheter is inserted and placed in the vicinity of the bifurcation of the tumor-feeding artery in the main trunk of the ECA instead of inserting a hook-shaped catheter, which is known as conventional IAC (CIAC, Figure 1c) [5]. It has been demonstrated that CIAC delivers a lower anticancer agent concentration to the tumor tissue compared to SSIAC [5]. Another issue with IAC is that the method to confirm the perfusion area of the agent in both CIAC and SSIAC has not been well developed. One confirmation method is to inject indigo carmine dye via the placed catheter [4; 12]. However, the staining is generally performed manually; hence, there is a possibility that the perfusion area of the anticancer agent cannot be reproduced by this method because the injection pressure of the dye by hand is quite higher than that by syringe driver, which is used to inject an anticancer agent. We believe that a new simulation is required, which allows clinicians to predict the distribution of anticancer agents among the ECA branches for each patient in advance of catheter insertion. Therefore, we have been using computational fluid dynamics (CFD) to elucidate the mechanism of anticancer agent distribution in IAC, because CFD has been widely used to investigate physical variables in the fluid phenomenon that cannot be reproduced experimentally.