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Background

Accuray is the global leader in the field of robotic radiosurgery.  They develop and market the CyberKnife® System.  This robotic radiosurgery system is designed to treat tumors anywhere in the body with sub-millimeter accuracy.

The CyberKnife System uses intelligent robotics to continuously track, detect and correct for tumor and patient movement throughout treatment. One element of the very complex system is the RoboCouch Patient Positioning System.  Accuray wanted the system to have greater range of motion to permit more patient treatment flexibility, specifically to allow the RoboCouch to easily accommodate a patient transfer.

Challenge

To design a seventh axis for the RoboCouch system.  The RoboCouch system had 6 axis of movement and a flat table for patients to be placed on during their procedures.  This seventh axis would bolt onto a standard mounting plate on the RoboCouch wrist, and run in continuous motion under the control of the existing robot controller.  Accuray gave us their specific requirements including mechanical envelope, system tolerances and development schedule.  We, in return, evaluated many different architectures and found one that would work for their envelope, weight, and schedule and that would utilize many off-the-shelf parts.

Solution

This was a collaborative engineering partner success.  The team worked closely with Accuray to refine all the elements of the axis.  Speck Design delivered the mechanical and robotic design as well as the electrical integration solution. We also designed the housing and surface and made all of this fit within their current configuration of the RoboCouch.

The RoboCouch ‘table’ had to hold 500 pounds plus a significant safety factor and change configuration from folded tabletop to a flat table.  Our solution had to fit in just 5 inches of space below the pedestal.  We at Speck Design try to look at our piece as a part of the whole, and with that in mind were able to beat the weight requirement by 1/3, freeing up an additional 100 pounds from the weight from the end of the arm, which benefited the complete system in terms of capability and factor of safety.

The new axis could potentially reduced patient setup times.  The patient surface, as it was designed before, it was a static flat surface. A patient, if mobile, would have to hop up on it or if they were not ambulatory, arrive in the lab on a gurney and be placed on the table.  Now the system allows the operator to lower the table into a chair like configuration to allow transfer from a wheelchair or the patient to just sit down and relax and have the system move you into place.  The table can remain folded to allow for increased patient comfort as well as providing additional options for positioning for procedures.

Speck Design conducted the stress analysis of all the major components as well as the drive system analysis.  Therefore, we identified the possible problem areas.  To be proactive, we designed into the system, a mechanical fail-safe to protect the components; a fuse in the system would break a connection before any component could be damaged. Detection of this overload condition triggers an emergency stop of the control system, preventing further damage or injury.

Results

Speck Design has extensive experience in mechanisms and systems design on robotics, arms, armatures in a wide range of fields including medical systems, robotics units, avionics and computing electronics, and industrial instrumentation.   Speck Design has developed key products for our clients both domestically and internationally and can assemble a very capable team to ensure a practical, innovative, and cost–effective delivery of projects.

PROJECT INFO

• Client:

  Accuray

• Project:

  Seventh Axis

• Industry:

  Medical