Shadowing a Doctor

March 26, 2014

A team has developed a tiny, wireless capsule that is capable of restoring the sense of touch that surgeons tend to lose as they increasingly shift from open surgery to laparoscopy or minimally invasive surgery.

First day in surgery! When performing any open procedure, surgeons typically depend on their sense of touch to identify the outer edges of hidden tumours and to locate hidden blood vessels and other anatomical structures. This procedure is called palpation. While palpation is possible during open surgery, it is not possible in minimally invasive surgery, which involves working with small, specialized tools and miniature cameras that fit through small incisions in a patient’s skin. 

A team of doctors and engineers at Vanderbilt University designed this special-purpose capsule to provide surgeons with the benefits of palpation while performing minimally invasive surgery. The wireless capsule is equipped with a pressure sensor that fits through the small ports that surgeons use for what is also called “keyhole” surgery

This capsule provides the physician with haptic feedback. In other words, it restores the surgeon’s sense of touch. Although the prototype is limited in that the information is still being provided on a computer screen, once the surgeon has the data, it can be used in a number of different ways. One possibility is using the capsule data with a haptic glove, which is commercially available. This would allow the surgeon to feel pressure that the capsule exerts and how the tissue responds to the stimulus, almost as if they are actually touching it.

Although minimally invasive surgery or laparoscopy has been around for more than a century, its use has grown substantially in the last 20 years after medical researchers demonstrated that it is not only safer but also less expensive as compared to open surgery for a number of different types of procedures.

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 they can easily grasp it and use it to map out the stiffness or density of the tissue, much like they would palpate it with by hand in open surgery.

Designed at Valdastri’s STORM (Science and Technology of Robotics in Medicine) Lab the palpation capsule is actually surprisingly simple. It is 2.4 inches long, 0.6 inches wide and contains an accelerometer, a pressure sensor, a magnetic field sensor, a wireless transmitter and a small battery.

When the end of the capsule is pushed against its target, the pressure sensor records the amount of pressure exerted and the accelerometer records its movements. The capsule is used with a fixed external magnet and its position is tracked precisely by measuring the direction and strength of the magnetic field it experiences. The wireless transmitter transmits all this information to an external antenna connected to a computer that uses the data to draw the map of tissue stiffness.

In initial tests, the researchers report that the capsule can measure the local stiffness of the tissue with a relative error lower than 5 %. The researchers’ goal is to achieve a level of resolution comparable to or greater than that of human touch.