Laser Tissue Bonding

Abstract

Scientific Research

Laser heating can be used to bond tissues. The exact mechanism of such laser welding or solding is not fully understood, but it has been found that it is critically dependent on the temperature of the tissue to be bond. We have developed a bonding system based on two optical fibers. One fiber is used to carry laser energy to heat a spot on tissue. The other fiber is part of a fiberoptic radiometer that is being used to determine the exact temperature of the heated spot. A computerized system makes use of the signal obtained from the radiometer to control the temperature. The temperature of a spot on a living tissue can be controlled to within 3°C .
We have conducted theoretical and experimental studied of the heating of tissues by both CO₂ laser (10.6µm) and GaAs diode laser(830nm). We found the optimal laser soldering conditions for cuts in tissues. Histological studies showed better results than standard suturing of cuts. Research is being continued now with different configuration of the laser soldering system in order to expend the capability of the system to solder tissues which we couldn't bond in the previous system configuration. In addition, research is being conducted on the soldering

People

David Simhon,
+972-3-7534100 ext 4104,
Office E-mail: simhont@013.net.il
TAU E-mail: davidsi@post.tau.ac.il
David Simhon, MD. , COO - IOPtima - Dr. Simhon is physician and near postgraduate PhD in clinical biochemistry, Sackler School of Medicine, Tel-Aviv University, Israel. He has extensive clinical experience as a residence in general and plastic surgery and in a burn unit. David has specialized in designing albumin-based biomaterials, tissue culturing and tissue engineering, as well as laser-tissue interactions. In recent years, David took part in collaborative R&D projects with medical device and biotechnology companies. Such collaborative efforts have greatly contributed to his development, clinical, and market orientation required in bringing a product from idea to the market.

Tamar Vasilev
+972-3-640-8405,
tamar999@post.tau.ac.il, 112,312,
Laser Tissue Soldering, M.Sc. In engineering and material sciense Currently reseach worker

Yaron Rabi
+972-3-640-8405
rabiy@post.tau.ac.il
Laser Tissue Soldering, B.Sc. Electrical engineering from Tel-Aviv Univ. M.Sc. Electrical engineering from Technion Currently PhD Studies

Ilan Gabay
+972-3-640-8405
gabayila@post.tau.ac.il
Shenkar 317
Laser Tissue Soldering, B.Sc. Physics and computer sciense from Tel-Aviv Univ. Currently M.Sc studies

Former Students

Lior Shapira, Lior.Shapira@nice.com, Laser Tissue Soldering, B.Sc. Electrical engineering from Ben-Gurion Univ. M.Sc. Applied Physics from Tel-Aviv Univ.
Avi Ravid, aviravid@soreq.gov.il, , Laser Tissue Soldering, M.Sc. and Ph.D. Applied Physics from Tel-Aviv Univ. Currently in Soreq NRC
Ophir Eyal

Selected Recent Applications:

Laparoscopic Laser Soldering of Ureter
We have developed a fiberopic CO₂ laser system designed to operate through a rigid or a flexible endoscope. We tested the system for the laparoscopic repair of Ureteral Pelvic Junction obstructions in the porcine model. The system worked well in a complicated surgical procedure and in a difficult environment, in the presence of blood and urine. The experiments in all pigs were successful, there were no any significant complications, and we obtained good physiologic and anatomic results. This is the first time that such a system has been used for endoscopic laser bonding of tissues in animal models.
Repair of Dura by Laser Soldering
We have developed a novel technique for dural reconstruction. This technique involves the soldering of a fascia patch to dura, and it would be useful for closing cuts or holes in the dura. The mean burst pressure was roughly 190 mm Hg, in comparison to the maximal pressure of CSF liquid in the brain, which is 15 mm Hg. A series of experiments on pig corpses clearly demonstrated that the method is very suitable for dural reconstruction. Long-term in vivo experiments were then successfully carried out on farm pigs. The animals were observed for a period of 10 days and no complications were noted. The histopathological results did not show any sign of thermal damage to the soldered tissue or to the underlying brain.
Laser Welding of the Skin
Skin laser soldering research is carried out by our group for several years. We already successfully soldered rat, rabbit and farm pig skin in-vivo. We now conduct a clinical trial on human skin in a after gall bladder laparotomy at HaEmek Hospital (Afula).

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Project Information
Surgical cuts may be bonded if heated by a laser beam. There are two main methods of laser tissue bonding: 1. Laser welding that based on heating of the approximated edges of a tissue ; 2. Laser soldering that based on applying some soldering material (such as albumin) onto the edges of the incision and heating the solder (and the underlying tissues) by a laser beam. One might unify both these techniques. Both laser welding and laser soldering are inherently non-tactile techniques, welding does not involve a foreign body (i.e. sutures, clips, staples or synthetic glues) and soldering engages a solder substance only. Both procedures offer, in principle, many advantages with respect to standard techniques: (1) a watertight bond; (2) a faster wound healing process; (3) potentially reduced scar formation; (4) easier accessibility to some specific areas in a body and (5) a procedure is both faster to apply and easier to master.
Even though laser soldering of tissue seems like a promising tissue bonding technique, it has problems that prevent it from being accepted as a common clinical practice. One of the main problems that should to be addressed is temperature control of bonded area. Another issue is reproducibility of the procedure. In order to achieve the satisfactory results, optimal soldering parameters have to be predetermined (i.e. laser power, temperature, solder type/thickness/concentration and so on). Further more, the use of this system in endoscopic application is limited by the dimension and configuration of the system.
In earlier work we found that to obtain reliable and strong bonding of cuts in tissues one has to apply biological solder, such as albumin, and heat the tissues under temperature control to roughly 60-65°C. The Applied Physics Group at Tel Aviv University has developed a several fiberoptic laser systems which can heat a spot on tissue (or on a solder layer) and keep its temperature constant to within 3-5°C. The principles of all of our systems are as follows:
(a) Laser Based Heating: The laser (either CO₂ laser or GaAs Diode laser or both) output power is coupled to a fiber whose distal end is fixed in a hand-piece. The laser energy absorbs either in the solder or in the tissue and rise its temperature. (b) Temperature Monitoring: The heated spot emits infrared radiation, whose intensity I is proportional to the temperature - T of the heated spot (according to Stefan-Boltzman law). For modest heating (less than 100°C) most of the radiation is in the mid-IR. This radiation is picked up by a AgClBr fiber ("sensor" fiber") and transmits to a pyroelectric IR detector. The signal V generates by the detector is proportional to the temperature T. The temperature measurements are carried out by this fiberoptic infrared radiometer in a non-contact fashion.
(c) Temperature Control: The signal V is read by a PC. A dedicated computer program is used to determine the temperature T. The PC modifies the laser power in order to maintain the predetermined set-point temperature. The temperature controlled laser soldering system is depicted schematically in the following picture.



Those systems have already been successfully used for laser soldering of different tissue types, including skin‎ (1), cornea(2), conjunctiva, trachea(3,4), bowel(5), urinary bladder(6), ureter(7), blood vessels(8) and dura(‎9,‎10). Examples of our work on bowel (movie 1) and conjunctiva (movie 2) is presented below.

Chronology

• 1994-2000: urinary bladder welding and soldering (in vitro and in vivo, CO₂) in rats and rabbits
• 1997: ocular tissue (cornea and choroid) welding (in vitro and in vivo, CO₂) pig
• 2001-2004: skin soldering (in vivo, CO₂ and GaAs), rat, rabbit pig. A clinical trial is permitted.
• 2001: closure of arteriotomy incisions in femoral vein of rat (in vivo, CO₂ )
• 2002: laparoscopic procedure for repair of ureteropelvic junction obstruction in the porcine model (in vivo, CO₂)
• 2004: end-to-end small bowel anastomoses in rabbit model
• 2005: pig trachea soldering using flexible albumin bands (in vitro, CO₂ and GaAs)
• 2005: reconstruction of dural defects by laser soldering of fascia patches to dura in porcine model (in vivo, CO2)
• 2006: end-to-end colon anastomoses (in vivo, CO₂; in vitro, GaAs)
• 2006: end-to-end conjunctiva soldering ( in vitro, GaAs)

Current Research

• Human clinical trials of skin cut soldering.
• Setting up new principle based temperature controlled laser soldering system.
• Tissue bonding mechanism research.
• Albumin characterization.
• Fiber optic based laser tissue ablation system.

References

1. Simhon, D., Halpern, M., Brosh, T., Vasilyev, T., Ravid, A., Tennenbaum, T., Nevo, Z., and Katzir, A., "immediate tight sealing of skin incisions using an innovative temperature controlled laser soldering device: in-vivo study in porcine skin," Ann.Surg., vol. 245, no. 2, pp. 206-213, 2007
. 2. Strassmann, E., Loya, N., Gaton, D., Ravid, A., Kariv, N., Weinberger, D., and Katzir, A., "temperature controlled CO2 laser soldering of pig cornea," Proc.SPIE, vol. 4609, pp. 222-228, 2002.
3. Shapira, L., Rabi, Y., Vasserman, I., Vasilyev, T., Sharvit, D., Hardy, A., and Katzir, A., "icg dyed albumin and diode laser heating for soldering of the trachea," Proc.SPIE, vol. 6078, pp. 172-176, 2006.
4. Sharvit, D., Vasilyev, T., Vasserman, I., Simhon, D., Kariv, N., DeRowe, A., and Katzir, A., "CO₂ temperature controlled laser soldering of pig trachea incisions in vitro using flexible albumin bands," Proc.SPIE, vol. 5686, pp. 242-247, 2005.
5. Simhon, D., Kopelman, D., Hashmonai, M., Vasserman, I., Dror, M., Vasilyev, T., Halpern, M., Kariv, N., and Katzir, A., "end-to-end small bowel anastomosis by temperature controlled CO2 laser soldering and an albumin stent - a feasibility study," Proc.SPIE, vol. 5312, pp. 176-185, 2004.
6. Lobel, B., Eyal, O., Kariv, N., and Katzir, A., "temperature controlled CO2 laser welding of soft tissues: urinary bladder welding in different animal models (rats, rabbits, and cats)," Lasers Surg.Med., vol. 26, pp. 4-12, 2000.
7. Shumalinsky, D., Lobik, L, Cytron, S., Halpern, M., Vasilyev, T., Ravid, A., and Katzir, A., "laparoscopic laser soldering for repair of ureteropelvic junction obstruction in the porcine model," J.of Endourology, vol. 18, no. 2, pp. 177-181, 2004.
8. Leshem, D., Vasilyev, T., Ravid, A., Gat, A., Kariv, N., Katzir, A., and Gur, E., "CO2 laser soldering of arteriotomy incisions in blood vessels of rats, using a temperature-controlled fiber optic system," Proc.SPIE, vol. 4949, pp. 199 -206, 2003.
9. B. Forer, T. Vasilyev, T. Brosh, N. Kariv, Z. Gil, D. M. Fliss, and A. Katzir. Repair of Pig Dura In Vivo Using Temperature Controlled CO2 Laser Soldering. Lasers in Surgery and Medicine 37 (4):286-292, 2005.
10. B. Forer, T. Vasilyev, T. Brosh, N. Kariv, L.L. Trejo, Z. Gil, A. Katzir and D. M. Fliss. Dural defect repair with fascia by a CO2 laser system in a porcine model. Laryngoscope. 116(6), pp.1002-6, 2006.