COMPUTER GUIDANCE SOFTWARE FOR NAVIGATION AND ASSISTANCE FOR SINGLE INCISION BIMANUAL ROBOTIC SURGERY

Carbone M.a,b*, Turini G.a, Petroni G.b, Niccolini M.b, Menciassi A.b, Ferrari M.a, Mosca F.a, Ferrari V.a

*Corresponding author: email: marina.carbone@endocas.org

Surgical robotics evolution is following the progresses of Minimally Invasive Surgery (MIS) which is advancing to Single-Incision Laparoscopic Surgery (SILS). The SILS approach allows less morbidity and improved cosmesis for the patient but imposes an unnatural arrangement of the instruments, thus resulting in difficult maneuverability due to the relative pivoting of the instrument tips inside the abdominal cavity. The robotic approach for SILS with the da Vinci Surgical System®, thanks to its wristed instruments, helps in overcoming this limitation, but there are a lot of issues to be solved in robot arms positioning both to avoid external collision when working coaxially and to deal with the different arrangement of instruments. On one hand the research goes in the direction of innovative instruments to be used with the actual surgical robot. (e.g VeSPA surgical instrument from Intuitive Surgical). On the other hand a more pioneering trend in research is to develop completely novel robotic platforms: bimanual robots that employ a couple of anthropomorphic arms and bring all the degrees of freedom (DOF) inside the abdomen.

Bringing all the DOF inside the abdomen eases the surgical gesture and increases the workspace reachable with the end effectors, but it introduces additional challenges to be faced. One of the main issue is the risk of unwanted collisions between the arms and the anatomies not involved in the intervention. In fact, during the execution of a SILS robotic intervention it is mandatory for the surgeon to be aware of the position of each part of the robot arm.

This can be difficult considering that the surgeon focuses very close to the instruments tips, with the risk of the loss of the absolute relationships with the entire anatomy. Surgeon’s orientation is generally very difficult both in traditional and in robotic laparoscopy.

Surgical navigators could overcome this limitation enabling additional viewing modalities thanks to the fusion of patient specific 3D models reconstructed from pre-operative images and virtual models of the surgical instruments inside a virtual scenarios.

While commercial surgical navigators are nowadays limited to few surgical applications many research groups are facing development challenges on building assessed surgical navigators.

Fig. 1 An overview of the Computer Guidance Module during a test session: a) The ARAKNES robot approaching the anatomy (mannequin), b)the

interfaces used to teleoperate the robot, c) the vision system 3D (left) monitor and our Computer Guidance Module (right).

This abstract describes the Computer Guidance Software for Navigation and Assistance developed in the context of the European ARAKNES project(www.araknes.org).

The ARAKNES project aims at realizing a robotic surgical system for endoluminal and SILS interventions; the whole platform is based on a bimanual robot composed by two 6 DOF arm attached at their base teleoperated by the surgeon using a console provided with custom handles (two Sensable® PHANTOM Omni® haptic devices ) and 3D vision (integrated 3D camera from STORZ). This main system is enhanced with additional modules for: preoperative Planning and Simulation, Computer Guidance and Intraoperative Diagnosis.

a Authors affiliations: a) EndoCAS Center, University of Pisa, Pisa, Italy

b) The Biorobotics Institute, Scuola Superiore Sant’Anna, Pisa, Italy Authors mail: marina.carbone@endocas.org, giuseppe.turini@endocas.org, g.petroni@sssup.it, m.niccolini@sssup.it, a.menciassi@sssup.it, m.ferrari@med.unipi.it, f.mosca@med.unipi.it , vincenzo.ferrari@endocas.org.

The Computer Guidance Workstation is connected to the robot workstation and receives data related to the robot base position in real time through a 6 DOF Aurora® sensor coil and the NDI Aurora® magnetic localizer, while data regarding the robot joint arms and the end-effector state (opening angle) are received directly from the Master Workstation that controls the real robot through a dedicated network. An overview of the system at work is represented in Fig. 1.

The whole platform is a multithreaded application that deals with four processes: the GUI and graphic rendering, the real-time tracking (for implementing a registration procedure based on a rigid approach), the network communication manager( to deal with data relative to robot joints angles), and the collision detection thread (to monitor the position of robot arm links in respect to the anatomy).

Our software module provides intraoperative navigation functionalities working in three different modalities: passive as a surgical navigator, assistive as a guide for the single port placement and active as a tutor preventing unwanted collision during the intervention (Fig. 2).

In the passive modality the surgeon navigate in a complete view of the virtual anatomy (patient specific 3D models) and of the virtual bimanual robot moving coherently with the real one in the same virtual scenario.

The visualization of the virtual scene aims to improve the surgeon performance allowing him/her to avoid visual occlusions (the module enables the surgeon to hide selected anatomies in order to see hidden structures), to change the point of view (the user can freely modify the viewpoint of the virtual scene) and additionally the module allows to select the same viewpoint of the real robot stereo endoscopic camera.

The assistive modality can be used in the initial phase of the procedure: when the surgeon has to place the access port. The computer guidance module is able to mark the virtual anatomy showing the correct port placement point (decided during the preoperative planning through a dedicated software), making easier and faster this critical and time-consuming phase.

Finally during the surgical intervention, the computer guidance module (working in active modality) can prevent unwanted collision with delicate organs (e.g. vessels). When the module detects a possible collision a visual and acoustic warning is sent to alert the surgeon that a robot arm is too near to a dangerous area (Fig. 4). In the early phase of the intervention the surgeon can arbitrary select the structures that he/she want to be elected as critical, and the software will configure consequently to send an alarm whenever a part of the robot links is too close to them.

The Computer Guidance Software was tested during some simulated surgical tasks of a cholecystectomy performed on a synthetic anthropomorphic mannequin. It showed good results in term of usability and performance (latency, visual quality and frame rate), whereas the registration accuracy is acceptable, at least using a mannequin.

Surgeons’ opinions were collected resulting in general encouragement. On one hand our software enables the surgeon to easily navigate into the patient anatomy relying on the virtual view offered by the system. On the other hand, the application offers the surgeon also assistive functionalities to facilitate the port placement and active functionalities to preserve the safety of delicate organs during the intervention. This functionality is particularly important for all robots that bring all the degrees of freedom inside the abdomen (the trend of robotic SILS). For this kind of robots, as demonstrated during our tests, the risk of unwanted collisions between the arms and the anatomies not involved in the intervention it is real. All the three categories of functionalities that we described, passive, assistive and active are important for a safe employ of similar robots. For this reason the software architecture is flexible, allowing to easily change the robot design in order to deploy the software with any surgical bimanual robot.

Fig. 2: LEFT - In the passive modality it is possible to switch between a global point of view, movable by the user, and the viewpoint of the real robot endoscopic camera (up Vs down). CENTRE - In the assistive modality the surgeon loads the access port position previously decided using the simulator software. The optimal port placement is showed on the virtual scene (an oriented cyano sphere), assisting to replicate the same position and orientation. RIGHT - In active

modality the system visually (red semaphor pointed by the arrows) and acoustically alerts the surgeon when a robot part is approaching delicate organs. The top image shows a panoramic view where the “elbow” of the robot is about to hit

pancreas and arterial vessels, this is difficult for the surgeon to realize just working with the endoscopic view (down).