Avi Ravid

Immediate tight sealing of skin incisions using an innovative temperature-controlled laser soldering device: in vivo study in porcine skin.

Background:A feedback temperature-controlled laser soldering system (TCLS) was used for bonding skin incisions on the backs of pigs. The study was aimed: 1) to characterize the optimal soldering parameters, and 2) to compare the immediate and long-term wound healing outcomes with other wound closure modalities. Materials and Methods:A TCLS was used to bond the approximated wound margins of skin incisions on porcine backs. The reparative outcomes were evaluated macroscopically, microscopically, and immunohistochemically. Results:The optimal soldering temperature was found to be 65°C and the operating time was significantly shorter than with suturing. The immediate tight sealing of the wound by the TCLS contributed to rapid, high quality wound healing in comparison to Dermabond or Histoacryl cyanoacrylate glues or standard suturing. Conclusions:TCLS of incisions in porcine skin has numerous advantages, including rapid procedure and high quality reparative outcomes, over the common standard wound closure procedures. Further studies with a variety of skin lesions are needed before advocating this technique for clinical use.

Laparoscopic laser soldering for repair of ureteropelvic junction obstruction in the porcine model.

BACKGROUND AND PURPOSE Laparoscopic pyeloplasty is used for the repair of ureteropelvic junction (UPJ) obstruction. Our objective was to introduce laser soldering to this procedure. MATERIALS AND METHODS We developed a system based on a CO2 laser, an infrared detector, and two infrared transmitting optical fibers to obtain temperature-controlled laser soldering of cuts in tissues. The system was used for laparoscopic soldering of incisions in the kidneys of pigs. RESULTS We carried out laparoscopic pyeloplasty successfully in a porcine model using fiberoptic laser soldering. Laparoscopic laser soldering was found to be faster than suturing. It was easier to use and provided watertight bonding. CONCLUSIONS This technique will be useful in pyeloplasty as well as other laparoscopic surgical procedures.

Fibre Bragg Grating sensor for shock wave diagnostics

We measured the response of short FBGs to a weak planar shock wave. The combined effect of the Photo-Elastic effect and the FBG strain was estimated theoretically depending on its orientation with respect to shock front (for 1550 nm FBG, parallel: 0.9 nm/kbar, perpendicular: -1.4 nm/kbar). The experimental results imply that the FBG/fibre survives for more than 1 μs at 5 kbar shock stress, and that our assumptions about the FBG behaviour under dynamic loading are valid, though more work is needed to fully quantify the effect.

Temperature controlled CO 2 laser soldering of pig cornea

Objectives: To determine the feasibility and reproducibility of laser soldering of cornea using biolog ical solder and a fiberopitc temperature conrolled CO2 laser system. Methods: We developed a system based on IR fiber delivery of CO2 laser radiation, for heating a spot on tissue, a fiberoptic radiometer for non-tactile infrared thermometry of the heated spot, and a computer control of the temperature of the spot.Experiments were performed in vivo in 8 corneas of 12Kg piglets eyes, which had 180°, 6mm diameter corneal trephnation perforating cuts.Soldering was done on some of the cuts at a set temperature of 65°C, with adjuvant 47% albumin solder, and standard suturing was done on other cuts, as control.Macroscopic and histologic evaluation was then carried out. Results: On macroscopic examination, the corneas were centrally clear, with corneal neovascularisation only around the sutures.Histologic examination of piglets corneas one week, one month, two months and five months after soldering revealed stromal lamellae which were organized with a fewer inflammatory reaction, in contrast to marked inflammatory response in the suture controls. Conclusions: The laser soldering technology appears to be reliable for closure of large corneal perforating cuts, and may overcome some of the technical difficulties and disadvantages of conventional corneal suture technique.

Laser soldering of the cornea in a rabbit model using a controlled-temperature CO2 laser system

This study was to determine the feasibility and reproducibility of laser welding of cornea with a CO2 laser system capable of real times infrared fiberoptic radiometric control of tissue temperature. A fiberoptic radiometric temperature control system for the CO2 10.6 micrometers laser was developed that enabled a real time nontactile temperature measurement of welding surface. The system was tested on the cornea in 40 in vitro bovine eyes, and also in 6 in vivo corneas of rabbit eyes. Welds performed at a set point temperature of 65 degree(s)C, with or without adjuvant 50% albumin solder. Leaking pressure, surgical time and histologic evaluation were determined for welding and for suturing controls of 6 mm central corneal perforating cuts.

CO2 Laser Welding of Corneal Cuts with Albumin Solder Using Radiometric Temperature Control

Purpose: To examine the efficacy and reproducibility of CO2 laser soldering of corneal cuts using real-time infrared fiber-optic radiometric control of tissue temperature in bovine eyes (in vitro) and to evaluate the duration of this procedure in rabbit eyes (in vivo). Methods: In vitro experiment: a 6-mm central perforating cut was induced in 40 fresh bovine eyes and sealed with a CO2 laser, with or without albumin soldering, following placement of a single approximating nylon suture. A fiber-optic radiometric temperature control system for the CO2 laser was used. Leaking pressure and histological findings were analyzed and compared between groups. In vivo experiment: following creation of a central perforation, 6 rabbit eyes were treated with a CO2 laser with albumin solder and 6 rabbit eyes were treated with 10-0 nylon sutures. The amount of time needed for completion of the procedures was compared. Results: In vitro experiment: effective sealing was achieved by CO2 laser soldering. Mean (± SD) leaking pressure was 109 ± 30 mm Hg in the bovine corneas treated by the laser with albumin solder compared to 51 ± 7 mm Hg in the sutured control eyes (n = 10 each; p < 0.001). Mean leaking pressures were much lower in the corneal cuts sealed only with the laser without albumin solder (48 ± 12 mm Hg) and in the cuts sealed only with albumin without laser welding (6.3 ± 4 mm Hg) than in the cuts treated with laser welding and albumin solder. In vivo experiment: mean surgical time was 140 ± 17 s in the laser-treated rabbits compared to 330 ± 30 s in the sutured controls (n = 6; p < 0.001). A histopathological study of the rabbit corneas 1 day after laser soldering revealed sealed corneal edges with a small gap bridged by coagulated albumin. The inflammatory reaction was minimal in contrast to the sutured controls. No thermal damage was detected at the wound edges. Conclusions: CO2 laser soldering combined with the fiber-optic radiometer is an effective, reliable, and rapid tool for the closure of corneal wounds, and holds advantages over conventional suturing in terms of leaking pressure and surgical time.

Theoretical model simulating CO2 laser welding of tissues

3D finite difference computerized model was developed to simulate the thermal behavior of biological tissue irradiated with a CO2 laser beam. The model uses standard thermal processes and in addition takes into consideration water evaporation and the corresponding changes in the thermal properties of the tissue. The results contain a temperature and biological damage map of the irradiated tissue. Experimental results of test made on Lucite irradiated with CO2 laser fit very well the theoretical predictions. The model was then used for simulations of tissue welding and the results indicate that an improved method could be used for CO2 laser welding.

CO 2 laser soldering of arteriotomy incisions in blood vessels of rats using a temperature-controlled fiber optic system

Background and objectives: Conventional methods for microvascular anastomosis are normally based on suturing, using special thin nylon sutures. These methods suffer from major drawbacks, which include: anastomosis, which is not watertight, and sutures or clips that cause an inflammatory response. In order to obtain better results, we introduced a procedure based on CO 2 laser soldering. We tested the system on arteriotomy incisions in rat blood vessels, in vivo. Materials and methods: We used a fiber optic based laser soldering system, with a temperature control capability. Arteriotomy incisions of lengths 4±1mm were performed on the femoral arteries of 48 wistar rats: 24 rats in the control group (suture) and 24 rats in the test group (laser soldering). We conducted two follow-up periods: 7 days and 21 days after the surgical procedure, for each group. Flow tests and histology examination were done in order to evaluate the quality of the procedures. Results: The patency rate was 84% for both groups, soldered and sutured. The sutured group showed a significant foreign body reaction (p < 0.05), which was not observed in the soldered group. We found no evidence of thermal damage in the soldered blood vessels. Conclusions: We can conclude that laser soldering is a less traumatic procedure, compared with the conventional suturing technique. It is potentially a faster technique and easier to master.

Laser soldering of rabbit skin using IR fiber optic temperature control system

Laser soldering of tissues is based on the application of a biological solder on the approximated edges of a cut. Our goal was to use laser soldering for sealing cuts in skin under temperature feedback control and compare the results with ones obtained using standard sutures. Albumin solder was applied onto the approximated edges of cuts created in rabbit skin. A fiberoptic system was used to deliver the radiation of a CO2 laser, to heat a spot near the cut edges, and to monitor and control the temperature. Laser soldering was carried out, spot by spot.

Comparison of FBG responses to static and dynamic pressures

FBGs respond to external pressures in ways that reflect both the strain-optic effect and the geometrical variations, both induced by the applied pressure. While the response to static isotropic pressure is quite straight forward and intuitive, the response to anisotropic shock waves is much more complex and depends also on the relative orientation between the fiber and the shock propagation direction. We describe and explain experimental results for both cases.