Abstract
In laser tissue soldering (LTS), a protein solution is thermally denatured and cross-linked to obtain a strong bond between tissues or tissue and a wound dressing. However, if the extension of the heat-affected zone is too large, wound healing is impaired by thermal tissue injuries. Therefore, heat input and coagulation depth have to be limited. We investigate the influence of wavelength and beam profile on coagulation depth using a soft tissue phantom in case of weakly (980 nm) and strong (1540 nm) absorbed laser radiation. The soft tissue phantom is doped with polystyrene (PS) beads to obtain similar scattering properties as natural tissue. The propagation of the laser radiation in the phantom is simulated by Monte–Carlo method and the optical penetration (OPD) depth calculated from isophotes. The simulation results are compared with the experimental determination of the coagulation volume. The results reveal that scattering effect of tissues on laser radiation increases the losses of a Gaussian beam profile laterally leading to a half-sphere coagulation volume. The depth profile of the coagulation follows approximately the intensity distribution of the laser beams as long as scattering effects are weak. As scattering effects become significant, as for 980-nm radiation, the intensity distribution of the laser beam in the tissue deviates from the original one, leading to different profile of the coagulation depth.
Highlights
Laser tissue soldering (LTS) and laser tissue welding (LTW) are two similar procedures for photothermal tissue bonding
For the present setup of the coagulation experiments, the results show that for the laser source with 980-nm wavelength, the coagulation depth scales with the optical penetration depth (OPD), while for the laser source with 1540 nm, the coagulation depth exceeds the OPD
For 980-nm radiation, the energy transport inside the phantom sample is determined by light propagation, while for 1540 nm, it is mainly given by heat conduction
Summary
Laser tissue soldering (LTS) and laser tissue welding (LTW) are two similar procedures for photothermal tissue bonding. A thermally induced cross-linking of tissue proteins can be obtained after approximation of the edges of an incision and laser irradiation. In LTS, a protein solution is added which serves as glue or Bsolder^ between a wound surface and a dressing or patch. The protein solution is thermally cross-linked and bonds the dressing to the tissue. Due to reduced thermal damage to tissue, LTS is often preferred over laser tissue welding [1]. A thin tissue layer in the wound area is affected by the heat treatment. Laser tissue soldering is being investigated since many years.
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