## 4 In Vivo Experiment Results  
### Pig Hepatic and Splenic Arteries  
To measure the operator radiation exposure and the usability of the two master devices for the robotic systems, the starting and target points (target 1 = hepatic artery, target 2 = splenic artery) were set as shown in Figure 10. The experiments for the hepatic and splenic arteries were conducted three times per target per master device per operator. Figure 10: Starting point and the two target points in the pig hepatic artery (target 1) and splenic artery (target 2). Figure 11 shows the results of the radiation exposure measurements of the operator during the conventional and robotic procedures. For the conventional procedure for target 1, the radiation exposure was measured to be 4.38 \(\pm\) 1.95 uSv, whereas that for the robotic procedure for target 1 was measured to be 0.11 \(\pm\) 0.04 uSv. For target 2, the radiation exposure doses were measured to be 6.16 \(\pm\) 1.86 uSv and 0.12 \(\pm\) 0.06 uSv for the conventional and robotic VI procedures, respectively. In the hepatic and splenic artery experiments, it was observed that the robotic procedure reduced radiation exposure by about 97% compared to the conventional procedure. For the pig hepatic and splenic artery experiments, the NASA-TLX and SUS scores were used to evaluate the usability. The results of the overall workload score based on the NASA-TLX and the system integration score evaluation based on the SUS score are summarized in Table 1. The values indicate the mean and standard deviation of the usability scores for the two master devices for each target. The operators reported higher NASA-TLX scores for both target 1 and target 2 when using the 2 DOFs joystick-type master device, implying that this device is physically and mentally harder to operate. In addition, higher SUS scores were reported for both target 1 and target 2 when using the 2 DOFs ergonomically designed master device. In the case of the 2 DOFs joystick-type master device, the score was about 55 points for both target 1 and target 2. According to the SUS score evaluation criterion, the 2 DOFs joystick-type master device belongs to the \"marginal low\" category among the acceptability ranges. However, the ergonomically designed 2 DOFs master device received approximately 73 points for the SUS score for the hepatic artery target 1 and target 2. This score is considered \"acceptable\". Thus, the 2 DOFs ergonomically designed master device outperformed the 2 DOFs joystick-type device in terms of user work intensity and system integration. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Master Device** & **Usability Index** & **Target 1** & **Target 2** \\ \hline
2 DOFs ergonomically & NASA-TLX & 18.14 \(\pm\) 1.95 & 22.73 \(\pm\) 3.86 \\ designed master device & SUS score & 74.64 \(\pm\) 2.67 & 72.91 \(\pm\) 2.92 \\ \hline
2 DOFs joystick-type & NASA-TLX & 23.71 \(\pm\) 2.21 & 30.74 \(\pm\) 4.99 \\ master device & SUS score & 56.87 \(\pm\) 4.26 & 55.62 \(\pm\) 4.73 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overall workload and system integration scores for pig hepatic artery and splenic artery experiments (mean and standard deviation). Figure 11: Measurement results of the radiation exposure to the operators during conventional and robotic VI procedures. The measured radiation exposure during the procedure for (**a**) hepatic artery target 1; and (**b**) splenic artery target 2. In addition, Table 2 shows the average of moving distances of the two master devices and the number of retractions of surgical instruments during the process of selecting blood vessels to reach the targets. The lesser the moving distance and the number of retractions, the lesser energy the master device consumes. For both target 1 and target 2, the moving distance of the joystick-type master device was measured to be greater than that of the 2 DOFs ergonomically designed master device.