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A small, wireless capsule has been developed by a team of doctors and engineers at Vanderbilt University, Nashville, TN, that, they say, can restore the sense of touch that surgeons are losing as they shift increasingly from open to laparoscopy or minimally invasive surgery.

During open surgery, doctors use their sense of touch or palpation to identify the edges of hidden tumors and to locate hidden blood vessels and other anatomical structures. However, in MIS where surgeons work with small, specialized tools and miniature cameras that fit through small incisions in a patient’s skin, the sense of touch is blocked.

In order to return palpation benefits to minimally invasive surgery, the researchers designed a special-purpose wireless capsule equipped with a pressure sensor that fits through the small ports that surgeons use for this tyle of “keyhole” surgery.

Once in the body, the surgeon can grip the capsule with the jaws or wire loop on the end of the laparoscope he or she is using for the surgery and press the end of capsule against the target tissue. As the surgeon taps the capsule in different places, it sends information about its position and the force being applied to a computer that uses the data to produce a false-color map of the tissue stiffness. This map can reveal the location of tumors, arteries and other important structures that the cameras can’t see because they are covered by a layer of healthy tissue.

The palpation capsule is 0.6 inches wide and 2.4 inches long. It contains a pressure sensor, an accelerometer, a wireless transmitter, a magnetic field sensor, and 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. The wireless transmitter sends all this information to an external antenna connected to a computer that uses the data to draw the map of tissue stiffness.

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