# Risk Management for the Reliability of Robotic Assisted Treatment of Non-resectable Liver Tumors
## 3 Results
### HeRo Concept Residual Risk Estimation  
After the HeRo parallel robotic system design, the residual risks were evaluated together with other forms of risk which may be introduced by the robotic system. Table 4 defines the risks as well as their severity and probability. Figure 11: The concept of the HeRo parallel robotic system: (**a**) augmented into the medical environment; (**b**) CAD (computer aided design). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Associated Risk** & **Comments** & **Severity** & **Probability** & **Overall Score** \\ \hline \multirow{3}{*}{**RR1**} & \multirow{3}{*}{Linear positioning error} & The risk is reduced as the position is achieved & & & \\  & & using actuators which have known positions, & & & \\  & & and furthermore, the L-US probe monitors in & & & \\  & & real time the needle insertion & & & \\ \hline
**RR2** & Orientation positioning error & As the orientation error increases with depth, & & & \\  & & the severity is higher & & & \\ \hline
**RR3** & Insertion depth error & The insertion depth is achieved by a dedicated & & & \\  & & actuator and monitored with the-LUS probe & & & \\ \hline
**RR4** & I-US probe positioning does not respect the & The L-US probe positioning is controlled by & & & \\  & predefined trajectory & actuators and can be corrected if needed & & & \\ \hline
**RR5** & I-US probe is pressing too hard on the liver & The I-US module must use a force sensor to & & & \\  & & ensure the necessary safety & & & \\ \hline \multirow{3}{*}{**RR6**} & \multirow{3}{*}{I-US cannot reach the targeted area} & The robot is attached at the beginning of the & & & \\  & & procedure in a convenient way with respect to & & & \\  & & the patient & & & \\ \hline
**RR7** & The I-US probe applies pressure on the & An efficient solution to ensure the RCM has to & & & \\  & abdominal wall & be used & & & \\ \hline
**RR8** & The I-US probe movements are different than & This can occur when the RCM is improperly & & & \\  & & intended & & & \\ \hline \multirow{3}{*}{**RR9**} & incapability of performing the procedure (the & The robot is attached at the beginning of the & & & \\  & instruments cannot reach the specific liver & procedure in a convenient way with respect to & & & \\  & & the patient & & & \\ \hline \multirow{3}{*}{**RR10**} & Incapability of achieving the necessary & Based on the defined workspace, this risk is & & & \\  & orientation for the L-US probe & eliminated & & & \\ \hline
**RR11** & Incapability of achieving the necessary & Same as above & & & \\  & orientation for the therapeutic needle & & & & \\ \hline
**RR12** & The relative patient-robot position is changed & As the robot is attached to the operating table, & & & \\  & & this risk is eliminated & & & \\ \hline
**RR13** & The patient cannot be resuscitated in due time & The robot must have a quick removal protocol & & & \\ \hline \multirow{3}{*}{**RR14**} & \multirow{3}{*}{The needle insertion cannot be monitored} & The two modules should use the same & & & \\  & & controller which ensures that the pose of the & & & \\ \cline{1-1}  & & two instruments is known & & & \\ \hline \hline
**RR15** & Infection risk & A robot is generally covered with a sterile & & & \\ \cline{1-1}  & & plastic sheet, so this risk is eliminated & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Residual risk estimation.