Bladder cancer treatment gets robotic upgrade
NASHVILLE, Tenn., and NEW YORK – Treatment of bladder cancer, the sixth most common cancer in the US, hasn’t changed much in more than 70 years. It still involves crude instruments and contortion of the patient’s body to reach certain target areas. Collaborative research between Vanderbilt and Columbia universities aims to dramatically update this standard of care.
The team of engineers and doctors, headed by Vanderbilt mechanical engineering associate professor Nabil Simaan, developed a robotic platform with a flexible, articulated arm that can be inserted through the urethra. This gives surgeons a much better view of bladder tumors and makes it easier to remove them from the organ’s lining, a procedure called transurethral resection.
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.
“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,” Simaan said.
Usually, a rigid tube called a resectoscope is inserted through the urethra and into the bladder. It also is used to remove tumors restricted to the bladder lining. The instrument contains an endoscope that can provide a good view of the bladder lining directly across from the opening of the urethra, but to image other areas, the scope must be pressed or twisted into the patient’s body. This procedure must be repeated for tumor removal in less accessible areas.
If the surgeon determines that an invasive tumor has penetrated the muscle layer, the bladder is removed entirely.
That experience inspired Simaan to develop a more flexible system based on microrobotics.
Bladder cancer is expensive to treat, in part because tumors in its lining are exceptionally persistent, requiring continuous surveillance and repeated surgeries. Exacerbating the issue is the difficulty in accurately identifying tumor margins and failure to remove all cancerous cells.
“Because you are working through a long, rigid tube, this can be a difficult procedure, especially in some areas of the bladder,” said S. Duke Herrell, an associate professor of urologic surgery and biomedical engineering at Vanderbilt University Medical Center who is collaborating on the project.
The telerobotic system is designed to operate in this challenging environment with submillimeter precision. Its tip is 5.5 mm in diameter, and, because it is segmented, the tiny arm can curve through 180°, allowing it to point in every direction. At its tip are a white light source, a fiber laser for cauterization, a fiberscope for observation and tiny forceps for gripping tissue.
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.
Force-feedback, which measures the force acting on the tip when it comes into contact with tissue, also gives the device a sense of touch.
“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.
The team plans to use this precision to perform an en bloc resection: the removal of an entire tumor plus a small margin of normal tissue in one operation to ensure that no cancerous cells are left behind.
The telerobotic system’s camera system is limited by poor distance resolution, something the team says can be corrected by redesigning the fiberscope or by replacing it with a miniature camera tip.
In the future, the researchers intend to incorporate additional imaging methods to improve the system’s ability to identify tumor boundaries, including a fluorescence endoscope, optical coherence tomography that uses infrared radiation to obtain micrometer-resolution images of tissue, and ultrasound to augment the surgeon’s natural vision.
The work is described in the April issue of IEEE Transactions on Biomedical Engineering.
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