Robotic System
The device that was tested was the LibertyR 3 system (Microrobot Medical Ltd, Yoqneam, IL). The LibertyR 3 is a non-commercially available, new endovascular robotic system, currently undergoing pre-clinical evaluation. Figure 1 and Fig. 2 display the primary components, which comprise of the bedside robotic drive (battery operated), the hand-held remote-controller unit, and the bedside-mounted articulated robotic arm. With the exception of the robotic arm which is composed of three foldable parts, with respective lengths of 25 cm, 25 cm and 20 cm, allowing the convenient and flexible usage, each of the components is designed for single-usage and is completely disposable. The weight of each component does not exceed 1.5 kgr (0.8 kgr for the robotic drive, 0.3 kgr for the remote control and 1.5 kgr for the robotic arm).
Porcine Model
In compliance with international laws for the protection of laboratory animals, the procedure was carried out at a certified animal laboratory. Veterinary professionals intubated and performed general anaesthesia to a single 60kg domestic pig, that was placed in supine position. At the completion of the experiment, all the contents were withdrawn, hemostasis was achieved with puncture site manual compression, and the animal was humanely euthanized.
Endpoints and definitions
The study’s primary efficacy endpoint was technical success defined as the capability to catheterize predetermined distal arterial branches (n = 11) in the kidneys (upper, interpolar, lower pole branch of the right and left renal artery), the liver (3rd generation branch of the right and left hepatic artery), and mesenteric arteries (three 3rd generation branches of the superior mesenteric artery), under fluoroscopy guidance, by manipulating micro guide wires and catheters used in coil and liquid embolization, in linear and rotational motion, and at varying speeds. The primary safety endpoints were the visual estimation of the occurrence of angiographic acute catheterization-related complications (dissection, thrombosis, embolism, perforation) and was compared to manual non robotic manipulations, and the evaluation of the immediate disconnection mechanism of the robot to allow manual operation.
Further parameters evaluated were: (a) characterization of the ease of use and operational performance of the Liberty 3 System by the 2 specialty physicians using prespecified scoring criteria (ease of remote control configuration, ease of guide wire and catheter manipulations) on a 1 to 5 scale (5 = optimal) to obtain a subjective assessment from the operator, and intraprocedural parameters while catheterizing distal arterial branches within the liver, kidneys and mesenteric vessels, (b) evaluation of the sensitivity and stability of linear and rotational motion of the guide-wire, particularly the control at different speeds using the same 1 to 5 score (c) evaluation of the performance of the remote control, (d) evaluation of technical parameter including the mounting of the robot to the table, the loading sequence of micro catheter and guide wire into the robot and the mounting of the guide catheter holder bridging the vascular sheath and the robot, (e) time required for the catheterization of each predetermined vessel. Two interventional radiologists with 18 and 2 years of experience in endovascular procedures and with no prior experience with robotic systems, conducted the catheterizations.
Procedure
The procedures were carried out in the animal lab using a C-arm by two radiologists (S.S., O.M.Z.) with 18 and 2 years of training and experience, respectively, in image-guided interventions, and naive to any robotic device including the LibertyR 3.
Under sterile conditions and with ultrasound guidance, vascular access was obtained in the left common femoral artery with the use of an 8 Fr x 10 cm vascular sheath, that was sutured to the skin. Using a C2 Cobra hydrophilic catheter (Terumo, Japan), the right renal artery was manually catheterized. The proper catheter placement was verified with a control angiogram. The Liberty was loaded with a 2.4 Fr Pro-great microcatheter over a 0.016 guidewire (Terumo, Japan) and the guiding catheter holder was used to attach the loaded Liberty to the C2 Cobra catheter, using the guiding catheter holder. With the use of the joystick, the robotic system was guided to the distal upper pole, interpolar, and lower pole branches of the right renal artery. Tasks involving intensive robotic manipulation of the microcatheter and micro guidewire at these sites were performed as part of the study. After the successful robotically guided catheterization, the microcatheter and wire were retracted to the proximal portion of the artery, and a diagnostic angiography was conducted. Both interventional radiologists executed the same process on the distal left renal artery branches.
In order to manually selectively catheterize the celiac trunk, a 0.035-inch guidewire and a 5 Fr C2 hydrophilic catheter was used. After manually delivering the selective catheter into the common hepatic artery, a 2.4 Fr Pro-great microcatheter with the 0.016 GT guidewire was installed into the Liberty and attached to the C2 catheter. Robotic steering to the distal 3rd generation right hepatic artery and subsequent relocation of the microcatheter system to distal 3rd generation branches in the left liver lobe were both successfully accomplished. The guidewire and microcatheter were robotically rapidly retracted as part of the experiment, in the event of a code blue. The C2 catheter was then withdrawn in the aorta.
Using the same 5 Fr C2 hydrophilic catheter, manual selective catheterization of the proximal superior mesenteric artery was conducted, and a selective angiography verified the correct placement. To access the three distal 3rd generation branches of the superior mesenteric artery, a 2.4 Fr Pro-great microcatheter and 0.016 GT guidewire were attached to the Liberty and coaxially placed into the guiding catheter, following successful navigation to the distal portions of the artery. After retracting the microcatheter and guidewire, a control angiography was carried out to verify that no acute angiographic complications had occurred during the procedure. The robot's capacity of rapid transition to manual operation was also tested. This was done by evaluating how rapidly and efficiently the instruments can be disconnected from their placement in the robotic system.