Telerobotics Treats Bladder Cancer Better

Removing tumors from the lining of the bladder, a procedure called transurethral resection, could become more tolerable for the patient and easier for the surgeon using a telerobotic platform that is under development.

"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," said Nabil Simaan, an associate professor of mechanical engineering at Vanderbilt University, who headed the interdisciplinary collaboration with Columbia University.

Bladder cancer, the sixth most common form of cancer in the US, is the most expensive to treat in part because the tumors in the bladder lining are exceptionally persistent, requiring continuous surveillance and repeated surgeries. Difficulty identifying tumor margins and failure to remove all the cancerous cells also contribute to the disease’s persistence.

The new microrobotic platform, designed to be inserted through natural orifices — in this case, the urethra — provides surgeons with a much better view of bladder tumors for more accurate diagnostics and removal regardless of location.

The telerobotic system created by engineers and doctors at Vanderbilt and Columbia universities is only 5.5 mm in diameter and is shown in a glass flask about the size of a human bladder. Courtesy of Joe Howell/Vanderbilt.

The system “doesn't take the judgment out of surgeons' hands; it enhances their capabilities and hopefully gives them surgical superpowers,” said S. Duke Herrell, an associate professor of urologic surgery and biomedical engineering; he is a specialist in minimally invasive oncology at Vanderbilt University Medical Center and a collaboraor on the project.

The current method, which Simaan observed, involves inserting a rigid tube called a resectoscope through the urethra and into the bladder. The instrument contains several channels that allow the circulation of fluid, provide access for an endoscope for observation, and interchangeable cauterizing tools used to obtain biopsy tissue for evaluating the malignancy of the tumor and to resect small tumors. In some operations, surgeons replace the cauterizing tool with an optical fiber laser to destroy tumor cells.

Endoscopes can give a good view of the bladder lining directly across from the opening of the urethra, but inspecting the other areas is more difficult. Doctors 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 tumors in less accessible areas.

If the surgeon, using endoscopic observation or biopsy, determines that a tumor is invasive and has penetrated the muscle layer, a cystectomy is performed, which removes the entire bladder through an incision in the abdomen. This is most often done using a normal surgical robot. However, if the tumor is judged to be superficial — restricted to the bladder lining — then it is removed using a resectoscope.

“Because you are working through a long, rigid tube, this can be a difficult procedure, especially in some areas of the bladder,” Herrell said.

Close-up of the bladder cancer telerobot's end effector clearly shows the white light source, jaws to grip tissue and a laser to burn cancerous tissue that it contains. Courtesy of Simaan Lab.

The telerobotic system is designed specifically to operate in this challenging environment. The machine itself is the size and shape of a large Thermos bottle, but its functional end is only 5.5 mm in diameter and consists of a segmented robotic arm, which 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 fiber laser for cauterization, a fiberscope for observation and a tiny forceps for gripping tissue.

The position of the snakelike arm can be controlled with submillimeter precision, a level adequate for operating in clinical conditions, the investigators said. 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 fiberscope produced a 10,000-pixel image that was directed to a digital video camera system, providing close-ups of the bladder walls at favorable viewing angles. However, the testing revealed that the camera system's effectiveness was limited by poor distance resolution. According to the researchers, this can be corrected by re-designing the fiberscope or by replacing it with a miniature camera tip.

In the future, to improve tumor identification boundaries, the researchers intend to incorporate additional imaging methods such as a fluorescence endoscopy, optical coherence tomography and ultrasound.

The robot arm was given a sense of touch also. Using a technique called force-feedback, the scientists can measure the force acting on the tip when it comes in contact with tissue. Normally, tumors protrude from the surrounding tissue. Vanderbilt doctoral candidate Andrea Bajo used this fact to successfully design algorithms that allow the robot arm to accurately trace a tumor's edge by positioning the tip on the edge of a tumor and instructing it to move in the direction that maintains the same pressure.

“Surgeons can typically identify the gross visual margin of a tumor within a millimeter, but a robot like this has the potential of doing so with submillimetric precision, and additional technologies may actually be able to distinguish margins at the cellular level,” Herrell said.

Vanderbilt graduate student Andrea Bajo operates the bladder cancer telerobot in a glass flask about the size of a human bladder. Courtesy of Joe Howell/Vanderbilt.

The researchers plan to use 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 tumor.

The system's capabilities are also being used to design safety measures for the telerobotic system such as setting a maximum depth that the laser will cut. Even if the operator’s hand slips, the robot will not cut any deeper.

Developing these safety measures for surgical robotic systems interacting inside the human body is Simaan’s primary research goal.

Findings were published in IEEE Transactions on Biomedical Engineering (doi: 10.1109/TBME.2012.2226031).

For more information, visit: www.vanderbilt.edu or www.columbia.edu