Hybrid Snake Robotic Probe Reduces Need for Invasive Surgery

A group of engineers and researchers from MIT, Harvard, and Massachusetts General Hospital have designed a robotic probe that will make is easier for doctors to access hard-to-reach places while delivering medication or performing surgery.

Diseases like cancer tumors or disorders in organs can occur in hidden places within the human body. Using X-rays, doctors can pinpoint the location of malignant tissue or any other abnormality, but physically delivering medicine or taking a biopsy can be exceedingly difficult if the point of interest lies deep within tissue. Invasive surgeries, or multiple injections at different angles, can unnecessarily damage healthy tissue.

The device is called the Robotically Steerable Thermal Ablation Probe (RSTAP), and it was featured at this year's IEEE's International Conference on Robotics and Automation. The key to this device is that it only needs to be inserted once, and then simply repositioned at different depths and rotated, to reach multiple areas of interest within a 3D volume.

The probe itself is made up of a straight shaft, called a cannula, that contains a pre-curved Nickel titanium or Nitinol (a shape memory material) stylet that extends from it. The team presented the design of a screw-spline drive mechanism comprised of the profiled and threaded shaft with a specially designed nut that reduces the parts needed and significantly simplifies manufacturing and assembly. To obtain the optimal curve for the Nitinol stylet, the team derived an expression that relates the tolerance between the specialized nut and shaft to the angular backlash of the stylet. They used SolidWorks to confirm their results.

First the degrees of freedom of the probe are tested to make sure all designed movements can be achieved. Then, the patient's X-ray scan is uploaded and registered with the appropriate coordinates so the doctor can simply choose the destinations of the probe by clicking on a spot on the digital image. Lastly, they check to make sure the robot's actual coordinate system matches that of the digital X-ray, and the procedure can begin.

This instrument will make many surgeries significantly less invasive, which will hopefully increase the success of diagnosis and treatment. Applications are many for this tiny probe, and include injections, biopsies, and thermal ablations. Tests have been performed on dead bovine tissue, but no word yet on when it will be used on live humans.

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