2011

Removing Digestive Tumors With a Therapeutic Endoscopy Teleoperation Robot

Endo Tools Therapeutics (ETT) is a medical device company based in Brussels, Belgium that was established in 2008. The company was formed after an innovative research project started in 2004 at Erasme Hospital (Université Libre de Bruxelles) and the faculty of engineering (Beams department, Université Libre de Bruxelles), based on the need for gastroenterologists to have more degrees of freedom when maneuvering an endoscope.

altThe researchers focused on developing robotized flexible arms anchored on an endoscope to insert into the digestive tract. Those arms would move independently from the endoscope and would enable surgery from within the digestive tract. This would give surgeons and gastroenterologists a set of new “scarless” therapies like those used in obesity treatment and tumor resection.

The first part of the system is called Endomina, and consists of flexible arms that are inserted into the patient’s digestive tract. Endomina has multiple wires, which are pulled or pushed to move the arms like a puppet. The second part of the system, called Endofix, is a motorized medical station that connects to Endomina. Besides computational hardware, Endofix has several motors, two haptic joysticks, and a touch panel. Endofix motors move Endomina wires according to a calculation done on the movements performed by the gastroenterologist with the two haptic joysticks. Endofix has a visual human interface on the touchscreen panel that gives information to the user about the status of the operation, and also provides additional user controls. The gastroenterologist becomes a puppet master of what happens at the end of Endomina’s arms inside the digestive tract of the patient.

The device was prototyped with commercial off-the-shelf (COTS) industrial controllers using text-based programming and sensors interfaced via an industrial controller area network (CAN). When researchers started developing the final product, they evaluated four options for the job. They considered using a custom route because they had the capabilities and there would be no major technical challenges, but this option was rapidly discarded because of production, safety, delay, and reliability concerns.

The second option was to continue using the COTS controller from the motor vendor, but it was not powerful enough, and the text-based programming had shown too many limitations. The third option was to use rapid prototyping software, with an xPc target, but those options were discarded because they could not support a turnkey operation, they were expensive, and most importantly, going into production involves multiple operations and often a platform switch to reduce costs.

The fourth option was a solution using National Instruments (NI, Austin, TX) products, applying an embedded PXI system with a real-time operating system. The NI hardware consisted of a 4-slot PXI-1031 chassis containing a PXI-8101 2-GHz embedded real-time controller, a PXI-8512 one-port CAN interface, and a PXI-7811R reconfigurable FPGA board with 160 digital I/O. The CAN interface is used to control the motor controllers for the Endofix medical motorized station.

The hardware and LabVIEW programming software provided relative ease of graphical programming, real-time hardware and software, development and production with the same hardware and software at a reasonable price, turnkey operation of many hardware modules and no need to worry about drivers, hardware reliability, and responsiveness and knowledge of the NI staff.

Developing the Endofix Software

altEndofix consists of two separate sets of virtual instruments (VIs). The first set is a visual human interface developed in LabVIEW on a Windows XP-based touch panel. It provides the user with information about the status of the entire system during the operation, as well as additional controls. There is also a set of realtime VIs, developed with the LabVIEW Real-Time Module running on the PXI platform. These VIs handle the communication with all the actuators and sensors, perform all the movement calculations, and take care of safety measures.

Almost all communication is done via the CAN modules using the CANopen standard, which was implemented with an additional library. All the VIs were managed in the same LabVIEW project under the Source Control feature. Switching from HMI development to real-time system development, yet staying in the same programming environment with almost all the same features, was particularly useful and productive.

The new solution provided a safe, reliable, efficient system. Turnkey operation of all the hardware modules was provided. For example, plugging in the modules and having direct access with an easy-to-use driver was easy and efficient. The software could be ported to multiple hardware platforms, and many subVIs in the project run on both Windows and in LabVIEW Real-Time platforms. Because the VIs are hardware independent, a single version can be maintained and deployed on many targets. Moreover, this means the researchers can choose another less powerful platform for commercialization.

The modular architecture made it easy to add new functionalities throughout the project without having to redesign the entire system. Additionally, it was easier to meet regulations with graphical programming. The software architecture translates almost immediately into block diagrams. Moreover, the LabVIEW VI Analyzer Toolkit, the LabVIEW Unit Test Framework Toolkit, and the source code control tools were extremely useful to ensure good programming practices, VI validation, and a detailed development history, respectively. All these criteria were essential to meet regulatory requirements for medical device development.

This article was written by Martin Hiernaux of Endo Tools Therapeutics, Brussels, Belgium. For more information, visit http://info.hotims.com/34451-330.