Abstract
Understanding light transportation in skin tissues can help improve clinical efficacy in the laser treatment of dermatosis, such as port-wine stains (PWS). Patient-specific cross-bridge PWS vessels are structurally complicated and considerably influence laser energy deposition due to shading effects. The shading effect of PWS vessels is investigated using a tetrahedron-based Monte Carlo (MC) method with extended boundary condition (TMCE). In TMCE, body-fitted tetrahedra are generated in different tissues, and the precision of photon–surface interaction can be considerably improved via mesh refinement. Such improvement is difficult to achieve with the widely used voxel-based MC method. To fit the real physical boundary, the extended boundary condition is adapted by extending photon propagation to the semi-infinite tissue layers while restricting the statistics of photon propagation in the computational domain. Results indicate that the shading parameters, such as the cross angle, vessel distance, and geometric shadow (GS), of cross-bridge blood vessel pairs determine the peak characteristics of photon deposition in deep vessels by affecting the relative deposition of collimated and diffused light. Collimated light is shaded, attenuated, and partially transformed into diffused light due to the increase in vessel distance and GS of vessel pairs, resulting in difficulty in treating deep and shallow vessels with one laser pulse. The TMCE method can be used for the individualized and precise forecasting of laser energy deposition based on the morphology and embedding characteristics of vascular lesions.
Highlights
Understanding light transportation in skin tissues can help improve clinical efficacy in the laser treatment of dermatosis, such as port-wine stains (PWS) [1]
We can7 of 13 see a KTMC larger than 8% was observed at 0°–60° and 330°–360°, whereas KTMCE maintained less than 7.5%, not sensitive to angles
The axes of the two vessels are are along the y-axis
Summary
Understanding light transportation in skin tissues can help improve clinical efficacy in the laser treatment of dermatosis, such as port-wine stains (PWS) [1]. Compared with voxel-based medium discretization, a tetrahedron-based approach is ideally adaptable to modeling targets with curved boundaries or locally refined structures. The error by confused optical parameters between neighboring photons computing energy depositioncan in complicated domains with a body-fitted tetraheare incidentphoton along the cell boundary be avoided in TMC by introducing the distance dron mesh.[18,19]. Necessary to extend the TMCTMCE method suitable for computing photon energy deposition in complex to laser propagation in the complex structures of PWS vessels.domains with a body-fitted tetrahedron mesh. Skin models with parallel and cross-bridge vessels are is suitable for computing photon energy deposition in complex domains with a body-fitinvestigated via to identify regulations of photon transport in complex tissue regions. Skin models with parallel and cross-bridge vessels are investigated via TMCE to identify regulations of photon transport in complex tissue regions
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