Guest post, by Dr Jeff Bezemer
Surgeons, like all doctors, frequently palpate (from Latin palpare, ‘to stroke’ or ‘caress’), i.e. they examine the patient’s body by touch. Their touch is typically somewhat invasive in that they manipulate parts of the body with their hands to feel for specific formations inside the body. Outside the operating theatre, they touch to ‘see’ what’s inside the patient body by palpating through the patient’s skin (‘extracorporeal touch’). Inside the operating theatre, the surgeon can also touch -and see- what’s underneath the skin (‘intracorporeal touch’).
Traditionally, only those who were trained to open the body up had a chance to see inside the body. Optical technologies have changed this. Now, imagery is available providing instant, live pictures of bodies that can be shared with clinicians, the patient, and the general public. Many people have been shown X rays and CT scans. Anyone internet access can review detailed graphics of people’s guts. For example, on YouTube, patients have shared recordings from their laparoscopic or key hole operations, showing the original video that the surgeon used to perform the operation (see, e.g., ‘My Actual Gallbladder Surgery ((**GRAPHIC!!**))’.
Fig 1: Laparoscopic surgery (picture from Wikipedia)
The same cannot be said about touching inside the body. What is felt when touching, say, someone’s liver, cannot yet be shared through a technology. These haptic experiences remain the exclusive realm of the surgeon; and somewhat of a mystery to everyone else. To share their haptic experiences with their colleagues or with the patient, surgeons need to put them into words or some other means of communication, which is notoriously difficult, and not particularly illuminating, unless you have some kind of shared experiential framework, like surgeons do (see this paper for a discussion).
Which is not to say that the surgeon’s touch has remained unaffected by new technologies. Performing operations through small key holes, as many of them now do, means that one cannot touch the body directly with one’s hands anymore: In key hole surgery, touch is mediated by (prosthetic) implements. The implements may relay some of the pressures on its tip to its handle, and thus to its controller, but they are not designed to communicate haptic sensations.
Researchers in mechanical engineering and computer science from the University of Siena, the Italian Institute of Technology, and the University Pennsylvania are addressing this problem. For a recently published study, they developed a way of digitally communicating haptic sensations registered by a finger-shaped tactile sensor to a cutaneous display attached to the surgeon’s fingertip. They specifically studied the tactile sensations of making and breaking contact, contact location, pressure, and high-frequency vibrations.
They tested the model in the context of robotic surgery. In robotic surgery, surgeons use joysticks to control robotic arms with implements. As in laparoscopic surgery, possibilities for palpation are limited in this set-up. A surgeon can remotely press a very specific area in the patient’s body, but they won’t receive haptic feedback, which might otherwise help identify formations of interest, e.g. structures that are targeted for intervention.
Fig 2: Robotic surgery (picture from Wikimedia)
To test the model, the engineers designed a task derived from heart surgery, where surgeons need to identify the orientation of a small pin located below the surface of soft tissue. The pin was oriented to point in a particular direction at random. They asked 18 people to work out the direction of the pin under different conditions. In one condition they did not get any haptic feedback, as is the case in current practice. In other conditions they did get haptic feedback, using the set-up just described.
Fig 3: Pacchierotti, Prattichizzo and Kuchenbecker’s haptic feedback model (Pacchierotti et al., 2016).
They found that when provided with fingertip contact feedback, the participants were significantly better at correctly identifying the orientation of the pin. They also found that the participating individuals used two different types of palpation strategies: pressing their finger, and dragging their finger. Those who used the dragging strategy benefited from feeling the finger sensor’s vibrations significantly more than those using the pressure technique.
Fig 4: Pacchierotti, Prattichizzo and Kuchenbecker’s haptic feedback model in action.
As the researchers point out, there is still much more work to be done before a version of this model can be implemented. For example, the sensors are too big to fit through the key holes used to access the patient’s body. The sensors only register selected types of sensations. There is also a question about whether giving surgeons haptic feedback will improve the quality and safety of their work at all. Yet the study does give us a fascinating glimpse of what the future of robotic and laparoscopic surgery might look like. Looking back, the introduction of what was then a new technology –laparoscopy– meant that surgeons lost some possibilities for touch. Now, haptic technologies are clearing the way for a return to these possibilities.
Pacchierotti, D. Prattichizzo, K. J. Kuchenbecker. Cutaneous feedback of fingertip deformation and vibration for palpation in robotic surgery. IEEE Transactions on Biomedical Engineering, 63(2):278-287 (2016).