Controllers and Compact Drives for Minimally Invasive Brain Surgery

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In neurosurgery, a mistake of a few hundred microns can lead to brain damage that cannot be reversed. This danger has led to an increasing focus being placed on minimally invasive surgery. Here, Surgeons carry out operations utilizing increasingly advanced robots instead of lasers and scalpels.

The EDEN2020 project, funded by the EU, is allowing researchers to develop a robotically steered catheter that can accurately dose anticancer drugs directly to a brain tumor in situ. However, the system is only as beneficial as its ability to position the needle as directed.

When the specification of the motion controller and drives for the four-axis robotic system that steered the catheter was needed, researchers were looking for low EMI, compact, and high-performance components. They discovered them with Elmo Motion Control.

PLATINUM-MAESTRO The Ideal Controller for High Performance Multi Axis Technologies

PLATINUM-MAESTRO The Ideal Controller for High Performance Multi Axis Technologies

GOLD TWITTER The NANO Servo Drive that provides over 4000 qualitative Watts

GOLD TWITTER The NANO Servo Drive that provides over 4000 qualitative Watts

A Steerable Needle

The EDEN2020 system is established on the Programmable Bevel-tip Needle (PBN), a versatile needle that can progress through the brain along a specifically defined route that mitigates the damage of brain tissue.

The mission is for the robotic motion system to reference intraoperative ultrasound imagery and preoperative MRI scans while the operation is underway in order to create path commands. When the PBN reaches the tumor, it delivers a chemotherapy payload to the tissue.

The PBN is comprised of four interlocking longitudinal plastic segments nested together, each of which includes a drug delivery channel. The channel also holds a fiber-optic cable for the purposes of shape sensing.

Each part is driven at its distal end by an ironless motor. The system can make the tip of the needle curve by a particular amount by pushing one segment or another forward so that it slides over the rest. This system allows the needle to be delicately navigated through brain structures to reach tumors, even those that are deeply embedded.

The program is immense and requires high demands on performance. It is no easy matter to navigate the robotic, steerable catheter through the brain. The four-axis program needs a high level of accuracy and synchronization, as irreversible damage could be caused by any mistakes made.

The system must operate with an accuracy of 10 μm at the low level control range. Performance is only a segment of the whole challenge. Space is consistently at a premium in an operating theater.

The components utilized in the PBN need to be as compact as possible. They also need to be quiet, in terms of both audible noise and EMI. The operating rooms are filled with delicate instrumentation. Therefore, the robot must not impact any imagery or the signal of an important instrument.

Drives and Controllers

The four motors contained in the PBN each require a drive. Additionally, the system as a whole needs a high-performance motion controller to carry out path planning established on closed-loop feedback and input from the ultrasound and MRI units.

For a drive, the Imperial College team chose the Elmo Gold-Twitter (G-TWI) servo drive. With small dimensions of only 35 mm x 30 mm, the compact Gold Twitter drive is critical for reducing the total footprint of the portable surgery station.

Along with this, the servo drive’s very low EMI, as a result of a highly efficient pulse-width modulation (PWM) switching process, proved essential in this critical medical application.

As safety is a chief concern, the Gold Twitter, the smallest STO (SIL-3) certified drive available on the market, provides a major advantage. The system must analyze the MRI and ultrasound data to navigate the PBN, then autonomously direct the four segments of the needle to drive the payload to the tumor.

The process must occur reliably, accurately, precisely, and at very high speeds. For a controller solution, the Imperial College team selected the Platinum Maestro (P-MAS) multi-axis motion controller. The Platinum Maestro contains a multi-core processor and advanced multi-axis features, making it competent for use in highly synchronized systems.

The controller contains a library of motion algorithms to clarify the implementation and control of robots and machines that must be both quick and precise. The Platinum Maestro includes advanced fieldbus support, including EtherCAT, cycling at a rate of 250 µs in the Imperial project.

The system will be able to sense and perceive intraoperative, continuously deforming brain anatomy at unmatched accuracy, precision and update rates,” explains Professor Ferdinando Rodriqugez y Baena, Project Coordinator for EDEN2020. The Platinum Maestro encompasses many features to make it easy to use.

In addition to the core benefits of the Elmo Motion Control technology, a key factor in our choice of control solution for the project was the reduced development time,” says Eloise Matheson, a PhD candidate at the Mechatronics in Medicine Laboratory.

The P-MAS is an off-the-shelf motion controller that gives users several features and tools that make motion integration more efficient. Important features are the simple interconnection of the P-MAS to all drives, and automatic EtherCAT configurations to all nodes.

Along with this, being able to control all drive parameters at the P-MAS level helps to simplify frequent maintenance procedures, thereby reducing downtime.

The EDEN2020 project has ambitious plans for the future. To reach those goals, the Imperial College team needs to focus on guidance software, the PBN, and on integrating diagnostics into their system.

The team does not want to spend hours of engineering time simply getting motion elements to operate simultaneously. The Elmo Motion Control Gold Twitter drives and Platinum Maestro controllersprovide high performance and accuracy in compact, low-noise solutions. There are also special characteristics designed to simplify integration and increase ease-of-use.

As a result of these features, effective motion is certain. The group can focus its efforts on the critical business of revolutionizing neurosurgery and saving lives.

This information has been sourced, reviewed and adapted from materials provided by Elmo Motion Control Ltd.

For more information on this source, please visit Elmo Motion Control Ltd.

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