Robotic system for noscar gastrointestinal surgery

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Slide 1 : Robotic System for No-scar Gastrointestinal Surgery Presentation slides as a summary of the paper written by S.J.Phee et al. All the information and pictures are from the paper published on the International Journal of Medical Robotics and Computer Assisted Surgery Vol 4 page 15-22, 2008 All copyrights reserved.
Slide 2 : Introduction Background Flexible endoscopy is used to inspect and treat disorders of the gastrointestinal (GI) tract without the need for creating an artificial opening into the patient’s body. Conventional endoscopic tools can only perform simple surgical procedures, such as polypectomy and biopsy, due to the lack of manoeuvrability of the tool. Master-slave robotic surgery system, such as da Vinci surgical system, is invented to provide the surgeon multi-degree-of-freedom to perform the surgery more easily and accurately.
Slide 3 : Introduction Motivation More technically demanding surgical procedures, such as haemostasis for arterial bleeding, suturing to mend a perforation or fundoplication for gastro-oesophageal reflux, require more dexterity from the tools to be performed. For the development of Natural Orifice Transluminal Endoscopic Surgery (a.k.a. NOTES) through the transgastric pathway. NOTES is an experimental surgical technique in which surgical procedures can be performed using an endoscope passed through a natural orifice (mouth, anus, etc), then through an internal incision in the stomach, vagina, bladder or colon, thus avoiding any external incisions or scars.
Slide 4 : Methods A slave with two robotic arms and long flexible body is developed. The surgeon controls the slave robot by working on the master console. A computer console interprets the readings from the master console, which in turn gives instructions to the slave robotic system to perform the treatment to the patient. Both of the master console and slave robotic arms are designed to be anthropomorphic with the same DOF configuration. Each robotic arm has multi-DOF to perform dexterous and complicated tasks.
Slide 5 : Proposed System Layout
Slide 6 : The First Slave Prototype Tendon-sheath actuation mechanism is used to ensure the mode of power transmission to be long, narrow and flexible in form. Two antagonistic tendons control each DOF motion independently which actuated by one DC motor. The first model of the prototype was a trial to test out the trade-off between complexity and workspace, as well as the force output of the slave manipulators.
Slide 7 : The First Slave Prototype Two robotic manipulators are attached to the endoscope by using an attachment from outside. The 3D view can be seen on the left. Altogether there is 12 DOFs, 6 DOFs for each arm, which consisted of a simplified two-DOF shoulder model, a one-DOF elbow and a three-DOF wrist, as can be seen on the left.
Slide 8 : The First Master Prototype Ergonomics played an important part in designing the master device. As the slave manipulators resemble human arms, the anthropomorphic data of the surgeon’s arm were used as the control parameters in order to give the surgeon better perception in performing the joint-to-joint control of the slave. The mobility range of the master was constrained only at the upper arm, by the virtual plane formed by the shoulder joint and the to cable sensors. Other joints satisfied the full mobility range of the surgeon in their respective movements.
Slide 9 : The First Master Prototype Two cable-actuated position sensors were used to measure the two contributing rotations of the shoulder joint that cause the up–down and in–out movement of the upper arm. Two optical rotary encoders were used to measure the flexion and supination–pronation movement of the elbow joint. Another similar encoder was used for flexion–hyperextension movement of the wrist, and the finger grip came with an encoder inside the holder.
Slide 10 : The Second Slave Prototype After study of the initial prototype, the slave robot was modified in some aspects as shown below: The modeling of the slave was simplified to the form of a human arm from wrist to elbow, instead of the whole human arm. The overall length is reduced by one-third. Less tiring for the surgeon to perform the procedure, since he could rest his shoulders on a flat surface. Also removed the need for a universal joint for the mechanism, which was not efficient due to its complexity.
Slide 11 : The Second Slave Prototype Second slave prototype (left) and its 3D model view (right)
Slide 12 : The Second Slave Prototype Slave manipulator designed from human arm
Slide 13 : The Second Slave Prototype Workspace of the second slave manipulator was formed using the motion range of movement of the joint, simplified from -90° to +90°, although the slave could move beyond this range. The diagram can be used to access the effective region where both the slave manipulators can work together.
Slide 14 : Comparison Between Two Slave Prototypes
Slide 15 : The Second Master Prototype The master controller had to accommodate the changes in slave manipulator design. The master was designed in such a way as to follow the kinematic structure of the slave as closely as possible without any compromise in comfort and user-friendliness. The new master controller had the following improved features: The motion of the device was only controlled at the grippers attached to the user’s fingers. That meant the user could rest his/her elbow. The size of the linkages became smaller; thereby the weight of the master was reduced, to further reduce user fatigue. The base to gripper link length was also adjustable, making it possible for motion scaling mechanically, if necessary.
Slide 16 : The Second Master Prototype Second prototype of the master controller comparison with the slave (left) and the kinematic diagram of the master’s ball-and-socket joint (right).
Slide 17 : Software Control Dedicated computer software was used for the robotic system. It took in real-time readings from each encoder of the master device and processed it before sending out appropriate signals to actuate the respective motors to bring about the required movements. The system framework adopted a two-layered architecture. The bottom layer was the hardware control module, which used low-level drivers for hardware control. The top-layer modules were the kernel algorithms, which performed the signal processing to compensate for backlash and noise disturbances.
Slide 18 : Preliminary Experiments Dissection of the mucosa of the stomach walls of the pig was performed by using the slave manipulator. The left gripper grabbed a piece of tissue such that the right hook, a monopolar cauterization tool, could move in to dissect the flesh. Due to the use of a multi-DOF gripper, the gripper could easily orientate the flesh and expose the necessary site to be cauterized. A clean cut could be performed more swiftly using the slave manipulator than with the conventional method. The trial demonstrated that the slave manipulator had enough force and dexterity to perform an essential surgical procedure on the slippery gastric walls of a pig.
Slide 19 : Preliminary Experiments Below shows the operation conducted with the slave manipulator, using the actual images captured by the endoscope.
Slide 20 : Discussions One of the biggest problems in the tendon-sheath driving robot system control was the non-linear characteristics due to friction between the tendon and sheath. As a result, delays and movement hysteresis were noticeable, as can be seen in the relationship: where T0 is tendon pre-tension, L is the length of the tendon sheath, E is Young’s modulus, A is the cross sectional area of the tendon, and ? is a non-dimensional parameter indicating the total friction force acting on the tendon under unit tendon-tension.
Slide 21 : Discussions To improve the performance of the system, a pre-tension device was introduced so that the tendon was always in tension. To further reduce the movement delay of the slave, the software recorded the movement of each slave joint whenever a direction change was detected; additional actuator displacement was used to compensate for the backlash. Due to the difficulty in predicting tendon elongation, the positioning control for the slave system was an open-looped control. Therefore the control for the robotic system was wholly dependent on the vision from the endoscope and user experience.
Slide 22 : Discussions Another problem was the design of the gripper. The overall surface area appeared to be too big and it was not sufficiently effective to grip the walls of the stomach easily. The user had to try several times in order to achieve effective grip and manipulate the slippery stomach walls. The size of the end effectors was also too big and bringing the endoscope into the stomach required much preparation and time. It must be further miniaturized to be able to use it comfortably on human subjects.
Slide 23 : Conclusions A master–slave robotic system that could enhance gastrointestinal endoscopic procedures has been designed and built. The developed slave robotic system consists of a long and flexible body that allows it to follow the endoscope through human natural orifices. This characteristic has the potential to allow treatment such as suturing to be performed on the patient without the need for any incision. A user was able to apply the master–slave system to perform tasks such as grabbing and cutting, as well as picking and placing. Animal trials were performed in which the robotic system was successfully used to dissect the stomach mucosa of a live pig.
Slide 24 : Conclusions Future work will include incorporating force sensors and haptic devices into the robotic system. The aim is to enable the endoscopist to ‘feel’ as though the slave manipulators are his own hands. More studies and tests are required before the system could be used to open an internal incision to reach other organs, which would be a large step forward for NOTES.

 


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