# Risk Management for the Reliability of Robotic Assisted Treatment of Non-resectable Liver Tumors
## 2 Materials and Methods
### Identifying Risk Control Measures for the Treatment of Non-resectable HCC Tumors  
The necessity of a technical solution that enables targeted treatments such as HDR brachytherapy for HCC in a safe manner emerges from the relatively high probabilities of hazards (see Table 1). A parallel robotic system is proposed as the technical solution, and to proceed further into its design, an integrated medical protocol was developed with the aim to achieve the targeted treatment of non-resectable tumors performed in the operating room as a minimally invasive procedure. This also enables the definition of the technical characteristics of the robotic system and the specific motions for the guidance of instruments involved. The robotic assisted _medical protocol_ for the MIS procedure is as follows:  
1. **Diagnosis and preplanning** stage: 1. **Diagnostic:** This step refers to the patient's preliminary analysis where it is determined whether or not a hepatic tumor is non-resectable (the inclusion criterion). This step may require various diagnosis methods such as medical imaging, biopsies, etc. ;
2. **Establishing the optimal treatment:** The optimal treatment approach is established, which may be targeted brachytherapy, targeted chemotherapeutic agent delivery, or RFA;
3. **Trajectory definition**: The coordinate points of interest (e.g., insertion and target points) are established relative to an external system of markers (fixed on bone mark). The relative positioning of the liver and the markers will not change once the carbon dioxide is insufflated. Based on previously obtained imaging data, the I-US probe insertion coordinates are determined together with the insertion coordinates of the needles, the needle trajectories, and the target points. _Note:_ Due to possible displacement of the liver, most likely from the pneumoperitoneum described in point B.2. below (the difference in position from the volumetric information and the position in the real-time procedure), in most of the cases the predefined trajectories are only an idealization (some corrections are required during the actual medical procedure). 2. **Procedure Preparation** stage: 1. **Patient and robotic system registration:** The patient is positioned on the operating table, the markers are identified, and the robotic system is fixed such that the trajectories of interest are in the central zone of its workspace. The mathematical correlation between the robot coordinate system and the patient coordinate system is determined to achieve patient-robot registration. _Note:_ The robot-patient registration serves only as an initial guideline; during the procedure, the clinician will actively search the tumor using the I-US probe. 3. **Pneumoperitoneum creation:** The patient is prepared for the intervention by insufflating CO\({}_{2}\) up to a certain pressure that is maintained constant through the whole procedure. The pressure will create an empty volume inside the abdominal cavity, enabling instrument manipulation inside the patient body. The first incision is created to allow the insertion of a 10 mm trocar for the insertion of the laparoscopic camera (manually guided) which will monitor the whole procedure. 4. **The robotic assisted procedure**:
5. **Ultrasound probe insertion and tumor location:** After the patient is prepared and the laparoscopic camera is introduced, the robotic system guides the tip of the I-US probe such that it touches the patient's skin. At this point, the surgeons fix a 10 mm trocar, this being registered as the RCM point for the I-US probe guiding module, and the US probe is inserted until it makes contact with the hepatic parenchyma. After contact, the clinician actively searches and locates the tumor, and by knowing the approach plane of the needletrajectory and the tumor depth, the US probe is fixed in the same plane to enable needle monitoring during its insertion into the hepatic tissue. 2.