Thermal model for optimization of vascular laser tissue soldering

Abstract

Laser tissue soldering (LTS) is a promising technique for tissue fusion based on a heat-denaturation process of proteins. Thermal damage of the fused tissue during the laser procedure has always been an important and challenging problem. Particularly in LTS of arterial blood vessels strong heating of the endothelium should be avoided to minimize the risk of thrombosis. A precise knowledge of the temperature distribution within the vessel wall during laser irradiation is inevitable. The authors developed a finite element model (FEM) to simulate the temperature distribution within blood vessels during LTS. Temperature measurements were used to verify and calibrate the model. Different parameters such as laser power, solder absorption coefficient, thickness of the solder layer, cooling of the vessel and continuous vs. pulsed energy deposition were tested to elucidate their impact on the temperature distribution within the soldering joint in order to reduce the amount of further animal experiments. A pulsed irradiation with high laser power and high absorbing solder yields the best results.

Nanoshell assisted laser soldering of vascular tissue

“…A numerical study of the soldering procedure showed that a higher absorption coefficient of the scaffold in the range of about 300 cm −1 will lead to a steep temperature gradient between the inner and the outer surface of the vessel wall which strongly reduces the damage potential to the intima 8. Using the particles containing only 18 µg ICG/mg NS, it was however not possible to increase the absorption coefficient above about 200 cm −1 since a larger percentage of nanoshells in the polycaprolactone scaffold rendered the scaffold too brittle.…”

“…Still, there are some serious problems limiting its general clinical applicability. Our experiments have shown that the strength of a soldered tissue connection correlates strongly with the maximum temperature reached during the procedure 8. Therefore, precise temperature control is a major hurdle to be removed in LTS.…”

The ox-foot-model for investigating endoluminal thermal treatment modalities of varicosis vein diseases

“…to date, endoluminal therapeutic treatment techniques have been demonstrated in laboratory setups, as well as in workshops, e.g. : "endovenous treatment Modalities -Hands-On using the Ox-Foot-Model" at the 52 nd Jahrestagung der Deutschen Gesellschaft für Phlebologie in 2010. the OFM also has been used for training in surgical ligation and bypass-anastomosis techniques of vessels, and it shows potential for investigations concerning vascular tissue soldering (Bogni et al, 2009). As shown in Figure 6, the surgical education on the OFM for training the techniques of bypass-anastomosis or arterio-venous fistulas for dialysis could be easily performed under standardized conditions.…”

Binding of indocyanine green in polycaprolactone fibers using blend electrospinning for in vivo laser‐assisted vascular anastomosis

“…An important aspect is the lack of control on the temperature reached during soldering. Previous studies have shown that the strength of the tissue connection strongly correlates with the temperature profile . Dye‐enhanced LAVA is based on thermal heating involving localized absorption of laser light using chromophores.…”

“…An additional challenge that is provoked by the flow‐off of ICG is staining of circumferential tissue, causing its unintended heating. Few approaches have been tested to face the problem of unfixed absorber: ICG‐infused chitosan patches , biodegradable polymer films , ICG‐loaded nano‐shells that are integrated in the soldering scaffold made of solvent cast polycaprolactone (PCL) , and the usage of absorbing gold nano‐chromophores . However, most of these techniques still result in a flow‐off of the solder or require the use of fixation sutures.…”