"Our group is one of the few in the world that knows how to develop and produce special optical fibers, which, unlike ordinary glass fibers, are able to transmit invisible light in the infrared range," says Prof. Avraham Katzir
The technique used by doctors to fuse tissues - during surgery or following an injury - has not changed in essence for thousands of years. The modern surgeon, just like his predecessors over the generations, usually sews up the incision with thread and needle; And the result - the quality of the suture and the scar it leaves behind - depends on the skill and experience of the doctor.
Now researchers from Tel Aviv University propose a new method, which will allow the surgeon to achieve an excellent result: fusion of tissue cuts without stitches, using a laser beam. "The basic idea of fusing sections by heating with a laser beam is not new, it came up for the first time in the 60s," says Prof. Avraham Katzir, head of the applied physics group at the School of Physics and Astronomy. "Over the years, there have been many attempts to perform fusion in this way, but most of them did not go well. We believe we have found the key to a successful execution: strict control of the temperature of the area heated by the laser beam during tissue fusion."
In a recent study, in collaboration with Dr. David Varsano from the Tel Aviv Medical Center (Ichilov Hospital) and Dr. Irina Barkat from the Sheba Medical Center - both of whom hold senior positions in the Faculty of Medicine of Tel Aviv University, the innovative method was used to transplant corneas into eyes taken from animals after their death. The research was recently published in the journal Proceedings of SPIE.
In light of the great potential of the new method for tissue fusion, the Reuters agency (the largest news agency in the world) prepared an article on the subject, which was broadcast in more than one hundred and forty countries, and received great interest.
like a hard boiled egg
"We have been claiming for a long time that the reason for failure in tissue fusion using a laser lies in the temperature to which the incision is heated during the process," says Prof. Katzir. "In this sense, tissue fusion is similar to heating an egg: if you heat it to 20 degrees, nothing will happen to it; At a temperature of 70 degrees, it will turn into a hard egg; And at 200 degrees, you will get a burnt egg.
The exact temperature is therefore a critical factor in the entire procedure, but until today, in most studies dealing with laser fusion, the temperature was not measured at all, and was not taken into account. We assumed that the most appropriate temperature, which would allow the tissues to bond optimally, is 65 degrees Celsius - just like cooking a hard-boiled egg."
Based on this hypothesis, the researchers sought to develop a technology that would allow the doctor to measure and control the temperature of the tissues throughout the fusion process. To this end, they used a unique expertise of their group: the production of optical fibers capable of transmitting infrared light.
A fusion system based on a laser and two optical fibers
"Our group is one of the few in the world that knows how to develop and produce special optical fibers, which, unlike ordinary glass fibers, are able to transmit invisible light in the infrared range," says Prof. Katzir. "Such fibers, made from silver halide crystals (the same material used in photography films in the past), are non-toxic and insoluble in water, and there is approval to use them in medicine. To date, they have been tested by us in various medical systems, such as laser devices for cutting tissue during surgery, and rapid thermometers that measure body temperature in the ear.
A few years ago, the researchers at Tel Aviv University developed a new technique for tissue fusion, which relied on their unique knowledge, and combined two optical fibers of a special type: one optical fiber transmitted laser radiation that heated a point on the tissue intended for fusion; A second fiber, which was adjacent to the first fiber, was used to measure the temperature of that point; And a control circuit made it possible to maintain an optimal temperature of 65 degrees at the fusion point. The edges of the section were attached to each other, and the points along it were heated one after the other until complete fusion. In this way a strong fusion was obtained, and at the same time no thermal damage was caused to the cut area.
This system was tested at the time in the laboratory - first in dead tissues and then in live pigs. Among other things, promising results were obtained in the fusion of cuts in the skin: the cuts fused strongly, almost without leaving scars. Following the success, the Ministry of Health also approved experiments on humans, at the Emek Hospital in Afula, and two surgeons, Prof. Doron Kopelman and Dr. David Simhon, were mobilized for the task: they used the technique to fuse incisions left in the abdominal skin after laparoscopic surgeries to remove the gallbladder. Again, the method produced beautiful fusions with minimal scarring.
Technological innovation: two functions in one fiber
To improve their method, the researchers developed another innovation: they combined the two functions - tissue heating and temperature measurement - in one optical fiber. "When there is only one fiber, the movements of the surgeon's hand do not affect the measurements, and the percentage of success increases significantly," explains Prof. Katzir. The two expert eye surgeons, Dr. David Versano and Dr. Irina Barkat, tested the improved technology in the laboratory, on eyes taken from cows and pigs after their death. They removed part of the cornea, put it back in place using the innovative system, and then injected water into the eye and created a pressure 3 times greater than the natural pressure inside it. The results: the transplanted corneas showed great stability and did not detach from their place, and the water did not leak from the fusion line. Apart from that, no thermal damage to the cornea was observed in this case either.
"We are now waiting for approval to perform corneal transplant surgeries in live pigs, and later also in humans," says Prof. Katzir. "In the currently accepted method, the surgeon attaches the transplanted cornea to its place using stitches all around - a craft that requires great skill and precision. When the stitching is not completely symmetrical, the patient's vision can be affected, and stitches that are too coarse can cause pain over time. We believe that our new technique will allow even less experienced doctors to perform corneal transplants accurately and successfully."
In the future, the researchers anticipate many more uses for the new technology, which is based on a single optical fiber, including: tissue fusion in the brain and internal organs, microsurgery of tiny blood vessels, surgeries inside the body using robotic systems, emergency medicine and surgeries on the battlefield, plastic surgeries, otolaryngology surgeries in small children and more. "In fact, anywhere in the body where surgery is performed, it will be possible to achieve a better fusion in this way, without stitches, and with minimal scars," concludes Prof. Katzir.
