Saturday, 25 October 2014
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Device promises to 'restore touch' to keyhole surgery

Keyhole surgeons could soon “feel” the inside of their patients as if they were operating with their hands thanks to new haptic technology.

Researchers at Vanderbilt University in Tennessee have developed a wireless capsule that fits on the end of keyhole surgery (laparoscopy) instruments that are controlled from outside the body, in order to transmit data about the stiffness of internal tissues back to the surgeon.

This data is displayed as a map on a computer screen that can reveal the location of tumours, arteries and other structures the surgeon’s laparoscopic camera can’t see because they are covered by other tissue.

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But the researchers believe this could be adapted to work with a haptic glove that would enable the surgeon to effectively feel their way around the tissue to identify the edges of hidden structures, a procedure typically known as palpation.

‘This capsule provides physicians with haptic feedback – in other words, it restores our sense of touch,’ said Keith Obstein, one of the researchers and an assistant professor of medicine at Vanderbilt University Medical Center.

‘Because palpation is so important to surgeons, there have been several previous attempts to build instruments that can provide it. Our approach is much simpler because it isn’t attached to a rigid shaft like previous tools and so does not force the surgeon to make an additional incision in the patient to use it.’

Fellow researcher S Duke Herrell, associate professor of urologic surgery at Vanderbilt University School of Medicine, said the 2.4 inch (6.1cm) long device could be picked up by the surgeon’s instruments when it was needed.

‘The hope behind something like this capsule is that the surgeon will be able to place it inside the body through an existing incision and leave it in a position where it can be easily grasped and used to map out the stiffness or density of the tissue when needed, much like he or she would palpate it with by hand in open surgery.’

The device contains a pressure sensor that records how hard the end of the capsule is being pushed against its target and an accelerometer that records movement, powered by a small battery.

The capsule is used with a fixed external magnet and its position is tracked precisely by measuring the strength and direction of the magnetic field it experiences. A wireless transmitter sends this information to an external antenna connected to a computer that uses the data to draw the map of tissue stiffness.

In desktop testing with tissue simulated with silicone gel, the researchers reported the capsule could measure the local stiffness of the tissue with a relative error of less than five per cent. In large animal tests, they said they achieved a relative error of eight per cent.

They hope to eventually achieve a level of resolution comparable with human touch and get approval to test the device in clinical trials in the next five years.

The research was funded by the National Science Foundation and National Center for Advancing Translational Sciences, and was published in the journal IEEE Transactions on Biomedical Engineering.

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