# Risk Management for the Reliability of Robotic Assisted Treatment of Non-resectable Liver Tumors
## 3 Results
The second QFD phase is illustrated in Figure 8, and among the critical functions identified are those associated with the I-US probe motion inside the body (RCM principle) and the needle insertion on linear trajectories (pair of points), followed by decoupled positioning and orientation motions. For the medical procedure, decoupled motions have the advantage that they increase the precision (e.g., while the medical tool is orientated the position of the RCM is fixed, which, in turn, may reduce positioning errors). Figure 6: AHP sorted results. Figure 7: QFD Phase 1—Analysis of technical characteristics with quantifiable quality ones. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline \multicolumn{1}{c}{**Function**} & \multicolumn{1}{c}{**Observations**} \\ \hline \multicolumn{1}{c}{Mounting on the side of the table} & \multicolumn{1}{c}{Table mounting is preferred (instead of ground mounting) to maintain a constant position (robot/patient) when the table is moved.} \\ \hline \multicolumn{1}{l}{I-US probe attachment to the robot} & \multicolumn{1}{c}{The commercially available medical tools (I-US probe and therapeutic needles) must be mounted/denounted to/from the robot.} \\ \multicolumn{1}{l}{I-US probe positioning and orientation outside the body} & \multicolumn{1}{c}{Before manipulating the medical tools inside the body during the medical procedure, they must be positioned correctly outside the body for the medical tool insertion.} \\ \multicolumn{1}{l}{I-US probe motion inside the body} & \multicolumn{1}{c}{The I-US must be manipulated using the RCM concept, whereas the needles are always inserted on linear trajectories.} \\ \multicolumn{1}{l}{Needle insertion on linear trajectory} & \multicolumn{1}{c}{M monitoring the tissue resistance reduces the risk of needle bending during the needle insertion.} \\ \multicolumn{1}{l}{Real-time tissue resistance force monitoring} & \multicolumn{1}{c}{Using an intelligent algorithm which takes multiple real-time parameters as inputs increases the safety of the procedure and allows fast reactions for situations where trauma risk increases.} \\ \multicolumn{1}{l}{Decoupled positioning and orientation motions} & \multicolumn{1}{c}{Decoupling the motions may increase the precision since while the orientation is changed the Cartesian robot is stiff (there are fewer overall errors during the medical instrument manipulation).} \\ \multicolumn{1}{l}{Emergency instrument detachment} & \multicolumn{1}{c}{In case of hemorrhage or other complications, the surgeons must be able to intervene promptly.} \\ \multicolumn{1}{l}{Easy-to-use elements that allow fast instrument computing are required.} \\ \hline \multicolumn{1}{l}{Sterilization} & \multicolumn{1}{c}{The components that are in close proximity to the patient must be detachable for sterilization purposes.} \\ \multicolumn{1}{l}{Preprocedural positional optimization} & \multicolumn{1}{c}{The robotic system must allow positional corrections since the target points may change due to errors and tissue elasticity.} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Defined functions for the robotic system. The next step in the analysis refers to the evaluation of the functions that the robotic system has to achieve and the technical subsystems of the robotic system. Table 3 describes the subsystems which compose the robotic system, whereas Figure 9 illustrates the Phase 3 QFD. The technical subsystems which have the most influence in achieving the predefined accuracy and safety aspects are the instrument mounting subsystems and the actuation subsystem, followed closely by the positioning subsystems (for the XYZ positioning and YZ orientation). The final step in the analysis refers to the evaluation of the technical subsystems of the robotic system and its component parts.