Graduate student Andrea Bajo operates the telerobot in a glass flask the size of a human bladder (CREDIT: Joe Howell / Vanderbilt)

Telerobot prototype to aid bladder cancer treatment

A team of engineers and doctors have created a telerobotic platform to boost detection and removal of bladder cancer tumours.

The method doctors use to deal with the disease has remained largely unchanged for more than 70 years and treatment is incredibly expensive due to in part to the fact tumours in the bladder lining are exceptionally persistent and so require continuing surveillance and repeated surgeries.

But an interdisciplinary collaboration of engineers and doctors at Vanderbilt and Columbia Universities, headed by associate professor of mechanical engineering at Vanderbilt Nabil Simaan, intends to change that.

The team has developed a prototype telerobotic platform that can provide surgeons with a much better view of bladder tumours so they can diagnose them more accurately and also make it easier to remove tumours from the lining of the bladder regardless of their location: an operation called transurethral recession.

"When I observed my first transurethral resection, I was amazed at how crude the instruments are and how much pushing and stretching of the patient's body is required," says Simaan.

The traditional method, which Simaan observed, involves inserting a rigid tube called a resectoscope through the urethra and into the bladder, which contains an endoscope for observation and interchangeable cauterizing tools.

Although the endoscope can give a good view of the bladder lining directly across from the opening of the urethra, inspecting the other areas is more difficult and the medical team must press and twist the scope or push on the patient's body to bring other areas into view. These contortions are also necessary when removing tumours in less accessible areas.

“Because you are working through a long, rigid tube, this can be a difficult procedure, especially in some areas of the bladder," says S Duke Herrell, associate professor of urologic surgery and biomedical engineering at the Vanderbilt University Medical Center, who is collaborating on the project.

The telerobotic system is the size and shape of a large thermos bottle but its business end is only 5.5 millimetres in diameter and consists of a segmented robotic arm that can curve through 180 degrees, allowing it to point in every direction including directly back at its entry point.

At the tip of the arm is a white light source, an optical fibre laser for cauterization, a fiberscope for observation and a tiny forceps for gripping tissue.

The engineers report that they can control the position of the snake-like arm with sub-millimetre precision – a level adequate for operating in clinical conditions – and they have also demonstrated that the device can remove tissue for biopsies by gripping target tissue with the forceps and then cutting it off with the laser.

The system "doesn't take the judgment out of surgeons' hands, it enhances their capabilities and hopefully gives them surgical superpowers," says Herrell, who specializes in minimally invasive oncology.

The fiberscope produced a 10,000-pixel image that was directed to a digital video camera system, which because it is steerable, was able to provide close-up views of the bladder walls at favourable viewing angles.

The testing revealed the camera system's effectiveness was limited by poor distance resolution but the researchers say this can be corrected by re-designing the fiberscope or by replacing it with a miniature camera tip.

Among the factors that contribute to this persistence of bladder cancer is the difficulty of accurately identifying tumour margins and failure to remove all the cancerous cells so in the future, the researchers intend to incorporate additional imaging methods for improving the ability to identify tumour boundaries.

These could include a fluorescence endoscope, optical coherence tomography that uses infrared radiation to obtain micrometre-resolution images of tissue and ultrasound to augment the surgeon's natural vision.

In addition to these observational methods, the researchers have given their robot arm a sense of touch using a technique called force-feedback, by which they can measure the force acting on the tip when it comes into contact with tissue.

Normally, tumours protrude from the surrounding tissue. Vanderbilt PhD candidate Andrea Bajo used this fact to successfully design new algorithms that allow the robot arm in the device to accurately trace a tumour's edge. He did so by positioning the tip on the edge of a tumour and instructing it to move in the direction that maintains the same pressure.

"Surgeons can typically identify the gross visual margin of a tumour within a millimetre, but a robot like this have the potential of doing so with sub-millimetric precision and additional technologies may actually be able to distinguish margins at the cellular level," says Herrell.

The team plans to make use of this level of precision to program the robot to perform what surgeons call an "en-block resection:" the removal of an entire tumor plus a small margin of normal tissue in one operation, a procedure designed to ensure that no cancerous cells are left behind that can reseed the tumour.

The engineers are also using the system's capabilities to design a number of safety measures into the telerobotic system. For example, the operator can set a maximum depth that the laser will cut and so even if the operator's hand slips, the robot will not cut any deeper.

The device’s features and capabilities are described in an article titled "Design and Performance Evaluation of a Minimally Invasive Telerobotic Platform for Transurethral Surveillance and Intervention" published in the April issue of the journal IEEE Transactions on Biomedical Engineering.

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