Theoretical-Computational Model for
Follicular Photothermolysis Optimization
Advanced computational research combining Monte Carlo Multi-Layered methods and Finite Element Analysis to optimize laser hair removal procedures through precise dosimetry calculations.
Research Problem & Objective
Current laser hair removal practices face significant limitations including qualitative assessment biases using the Fitzpatrick scale, omission of radiative transfer effects, and lack of personalized treatment protocols.
Up to 19% of patients experience side effects such as hyperpigmentation and burns due to imprecise energy calculations and suboptimal treatment parameters.
This research develops a computational tool for precise dosimetry to enhance treatment effectiveness, minimize side effects, and enable personalized laser configurations.
Key Research Goals
- Develop precise computational dosimetry tool
- Minimize treatment side effects and burns
- Optimize laser parameters across skin phototypes
- Enable personalized treatment configurations
- Reduce treatment costs through optimization
Computational Methodology
Monte Carlo Multi-Layered (MCML) Method
Simulates photon propagation and radiative transfer within biological tissues, modeling absorption and scattering as photons interact with skin layers and hair follicles.
- • Statistical understanding of laser light penetration
- • Complex geometry and heterogeneous tissue modeling
- • Photon tracking through absorption and scattering events
- • Simulation of 144,000 photons across parameter combinations
Finite Element Method (FEM)
Solves the heat equation to model heat transfer in biological tissue, specifically targeting hair follicles with complex geometries discretized into finite elements.
- • Detailed temperature distribution modeling
- • Integration of laser energy absorption and heat diffusion
- • Complex geometry handling for hair shaft and skin layers
- • Global solution from combined local element solutions
Mathematical Framework
Heat Equation
Models temperature distribution within hair follicle during photothermolysis:
- • ρ: density
- • cp: specific heat capacity
- • k: thermal conductivity
- • μa: absorption coefficient
Radiative Transfer Equation
Describes radiation interaction with scattering and absorbing medium:
- • I(r,s): spectral radiance
- • μs: scattering coefficient
- • P(s,s'): phase function
- • dΩ': differential solid angle
Computational Process
3D Model Creation
- • 5-part skin model in Onshape
- • Hair follicle: 0.1mm radius sphere
- • Hair shaft: 0.03mm radius, 2.5mm height
- • Distinct optical & thermal properties
Mesh Generation
- • STL format export
- • Preserved dimensions & coordinates
- • No gaps between objects
- • FEM discretization preparation
Parameter Testing
- • 3 wavelengths: 750, 810, 1064 nm
- • 4 pulse durations: 10-75 ms
- • 4 fluence levels: 50-80 J/cm²
- • 48 parameter combinations total
Research Results
Optimal Laser Configuration
Key Findings
- Selective Targeting: Dermis-to-follicle photon absorption ratio of 1.13, indicating optimal selective destruction
- Improved Precision: Combined heat equation and radiative transfer provide more accurate energy estimation
- Side Effect Reduction: Minimized unnecessary energy absorption by surrounding tissues
- Clinical Validation: Results consistent with previous findings by Klanecek et al.
Clinical Impact & Applications
This computational framework enables personalized laser hair removal configurations, leading to improved clinical results, enhanced safety, and reduced treatment costs through optimized energy delivery and session planning.
The model provides a strong foundation for future clinical trials and technological advancements in laser-based dermatological treatments.