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Laser Use in Surgery: "Laser could replace the scalpel"
Doctor Florian Stelzle is a Specialist for oral and maxillofacial surgery at the University Hospital Erlangen, Germany, and participates in developing the tissue-specific laser; © Stelzle
The use of laser technology offers surgeons many advantages. Now researchers want to compensate for its biggest downside, the lack of haptic feedback. Doctor Florian Stelzle explains how this work – and what else could be improved in lasers.
Doctor Stelzle, what tasks does the laser take on today in surgery?
Stelzle: When it comes to very precisely cutting tissue, today the focused laser in part already replaces the traditional scalpel. Examples for these kinds of applications would be a partial liver resection or the removal of a tongue tumor. Another application for the laser is the general surface ablation of tissue, whether that’s in the oral cavity, the internal intestine or the bladder. We achieve this effect with a defocused laser beam, which removes the tissue in layers.
What are the advantages of lasers?
Stelzle: Surface ablation for example is something that can barely be accomplished with a scalpel due to mechanical reasons. Due to its design, we will always only be able to perform cone shaped cuts in the broadest sense with the scalpel. Compared with other procedures you can alternatively use for surface ablation – such as cryotherapy or heat coagulation – the laser also fares better, since it performs its task more precisely. And one really big advantage is the fact that I can attain different effects with the laser depending on wave length and energy: I can choose for example whether I close blood vessels during cutting – which is an advantage during the removal of a hemangioma –or not.
What limits and disadvantages does laser use have?
Stelzle: The laser works contactless. This is an advantage in almost every way and provides us with many freedoms – however, haptic feedback gets entirely lost and this is a fundamental disadvantage. When he uses a scalpel, the surgeon knows and feels precisely where he cuts and where a nerve he has to treat with care is approximately located. The different tissue structures can be clearly felt given a little experience. This information is completely missing in the case of the laser, once the surgeon works deeper – which is why most cases of application for the laser are thus far on the surface of tissue.
Which application areas could also be interesting for the laser?
Stelzle: Based on its potential, the laser is suited to cut any tissue in the body, even bones or hard tooth tissue. This also makes it outclass the scalpel. Its potential however is so far still not fully utilized due to the lack of haptic feedback, although the laser could some day make the leap to universal use and completely replace the scalpel.
You are participating in developing a tissue-specific laser. What type of improvement do you expect from this?
Stelzle:We want to replace the missing haptic feedback with technical feedback. To do this, we use a spectroscopic analysis of the reflected light on the newly ablated tissue as well as the analysis of the particle cloud that is generated during the ablation. We work on identifying skin, muscles, bones and nerves automatically – and this occurs during the short breaks the laser provides between the individual light pulses.
Have the technical questions for this project already been answered?
Stelzle: Not all of them, although we have already accomplished a lot. We can identify tissue in the model without blood flow as well as also in the animal model with well-perfused tissue. This was already an important step, since blood absorbs the most light. We also know that we can disregard the changes the laser beam itself causes to the tissue for the feedback system and tissue identification. The current challenges are in a math solution, which enables us to do an adequately fast analysis of the spectroscopic results. After all, we only have time periods in the microsecond area available for the analysis and today there are already lasers that work with even shorter breaks than our laboratory system. So we still have to speed up the analysis.
Why is this so important?
Stelzle: With each of the successive pulses that come in very short intervals, the laser ablates some tissue. If we want to be sure that our system does not attack a structure that needs to be preserved, it has to completely perform the analysis during the short break and potentially trigger the stop signal of the control system to stop the laser. This is the only way the surgeon can limit the ablation and the cut to the prior chosen tissue type. And this is also the only way we someday get to where the system will also become applicable to medical technology innovations such as for example robot-assisted surgery.
Will this system be suited for minimally-invasive surgery?
Stelzle: Lasers with specific wavelengths today are already used in vascular surgery for example. Flexible fiber optic cables which can be coupled into the endoscope like forceps or scissors are the prerequisite for this. Since we utilize optical analysis methods for the feedback, it can also be applied to endoscopic surgeries. In any case, the light reduction in the fiber-optic light guide does not interfere with the function.
Are there industrial partners already?
Stelzle: We are still moving in the area of fundamental research and collaborate intensively with the Bavarian Laser Center (“Bayerisches Laserzentrum“) as our project partner. As soon as we will approach the prototype phase and it will be all about applicable hand controls and similar details for example, experts from the medical technology sector are certainly welcome as additional partners.
It will be many years until marketability. What should be improved on existing laser systems in the meantime?
Stelzle: Flexible and small glass fiber cables and delicate hand controls would make our work in the operating room easier. A hand control used in dermatology is often too large for use in the oral cavity. Even if I want to direct the beam into another direction to for instance get under the tongue at a right angle, I can do it – but I have to pull back the hand control and put on an angular piece. That’s cumbersome. And there is something else, even if this normally makes engineers scream because of the technical requirements behind it: as surgeons we would like to have a laser whose wavelength we can modify – and please have it be integrated in the device.
The interview was conducted by Doctor Birgit Oppermann and translated by Elena O'Meara; from medizin & technik 05/11