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Spatial temperature distribution in human hairy and glabrous skin after infrared CO2 laser radiation.

Frahm KS, Andersen OK, Arendt-Nielsen L, Mørch CD - Biomed Eng Online (2010)

Bottom Line: The laser energy is absorbed by the water content in the most superficial layers of the skin.The simulations were compared to the subjective pain intensity ratings from 16 subjects and to the surface skin temperature distributions measured by an infrared camera.The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajers vej 7D-3, DK 9220 Aalborg, Denmark. ksf@hst.aau.dk

ABSTRACT

Background: CO2 lasers have been used for several decades as an experimental non-touching pain stimulator. The laser energy is absorbed by the water content in the most superficial layers of the skin. The deeper located nociceptors are activated by passive conduction of heat from superficial to deeper skin layers.

Methods: In the current study, a 2D axial finite element model was developed and validated to describe the spatial temperature distribution in the skin after infrared CO2 laser stimulation. The geometry of the model was based on high resolution ultrasound scans. The simulations were compared to the subjective pain intensity ratings from 16 subjects and to the surface skin temperature distributions measured by an infrared camera.

Results: The stimulations were sensed significantly slower and less intense in glabrous skin than they were in hairy skin (MANOVA, p < 0.001). The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001). Of the 16 subjects tested; eight subjects reported pricking pain in the hairy skin following a stimulus of 0.6 J/cm2 (5 W, 0.12 s, d1/e2 = 11.4 mm) only two reported pain to glabrous skin stimulation using the same stimulus intensity. The temperature at the epidermal-dermal junction (depth 50 μm in hairy and depth 133 μm in glabrous skin) was estimated to 46°C for hairy skin stimulation and 39°C for glabrous skin stimulation.

Conclusions: As compared to previous one dimensional heat distribution models, the current two dimensional model provides new possibilities for detailed studies regarding CO2 laser stimulation intensity, temperature levels and nociceptor activation.

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Related in: MedlinePlus

The figure illustrates the experimental setup and the parameters used for the finite element model. In A the laser beams spatial profile is seen in the infrared camera. The slight skewed look of the profile is most likely due to fact that the cameras line of sight was not perpendicular to the skin surface. But it could also be due to the poor spatial resolution of the infrared camera and an inaccuracy of the laser optics. However, a Gaussian fit of the laser beam showed that the laser beam fits a Gaussian profile with an r2 of 0.984. In B the experimental setup is displayed. It consists of a 100 W CO2 laser with a beam expander and scanner head. The latter directs the laser beam to the desired skin sites. In C the principle behind the finite element model is displayed including thermal constants, geometric sizes and simulation properties. The lower boundary is kept at a constant temperature (0°C). Note that the initial temperature in the model is 0°C. This mimics how the thermal energy deeper into the tissue which is the primary cooling effect during laser stimulation.
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Figure 1: The figure illustrates the experimental setup and the parameters used for the finite element model. In A the laser beams spatial profile is seen in the infrared camera. The slight skewed look of the profile is most likely due to fact that the cameras line of sight was not perpendicular to the skin surface. But it could also be due to the poor spatial resolution of the infrared camera and an inaccuracy of the laser optics. However, a Gaussian fit of the laser beam showed that the laser beam fits a Gaussian profile with an r2 of 0.984. In B the experimental setup is displayed. It consists of a 100 W CO2 laser with a beam expander and scanner head. The latter directs the laser beam to the desired skin sites. In C the principle behind the finite element model is displayed including thermal constants, geometric sizes and simulation properties. The lower boundary is kept at a constant temperature (0°C). Note that the initial temperature in the model is 0°C. This mimics how the thermal energy deeper into the tissue which is the primary cooling effect during laser stimulation.

Mentions: During the experiments the subjects were seated in a chair with the dorsum of their left hand and forearm placed flat on a table with the volar forearm perpendicular to the laser beam (Figure 1). The subject and investigator wore protective goggles for the duration of the experiment.


Spatial temperature distribution in human hairy and glabrous skin after infrared CO2 laser radiation.

Frahm KS, Andersen OK, Arendt-Nielsen L, Mørch CD - Biomed Eng Online (2010)

The figure illustrates the experimental setup and the parameters used for the finite element model. In A the laser beams spatial profile is seen in the infrared camera. The slight skewed look of the profile is most likely due to fact that the cameras line of sight was not perpendicular to the skin surface. But it could also be due to the poor spatial resolution of the infrared camera and an inaccuracy of the laser optics. However, a Gaussian fit of the laser beam showed that the laser beam fits a Gaussian profile with an r2 of 0.984. In B the experimental setup is displayed. It consists of a 100 W CO2 laser with a beam expander and scanner head. The latter directs the laser beam to the desired skin sites. In C the principle behind the finite element model is displayed including thermal constants, geometric sizes and simulation properties. The lower boundary is kept at a constant temperature (0°C). Note that the initial temperature in the model is 0°C. This mimics how the thermal energy deeper into the tissue which is the primary cooling effect during laser stimulation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2991325&req=5

Figure 1: The figure illustrates the experimental setup and the parameters used for the finite element model. In A the laser beams spatial profile is seen in the infrared camera. The slight skewed look of the profile is most likely due to fact that the cameras line of sight was not perpendicular to the skin surface. But it could also be due to the poor spatial resolution of the infrared camera and an inaccuracy of the laser optics. However, a Gaussian fit of the laser beam showed that the laser beam fits a Gaussian profile with an r2 of 0.984. In B the experimental setup is displayed. It consists of a 100 W CO2 laser with a beam expander and scanner head. The latter directs the laser beam to the desired skin sites. In C the principle behind the finite element model is displayed including thermal constants, geometric sizes and simulation properties. The lower boundary is kept at a constant temperature (0°C). Note that the initial temperature in the model is 0°C. This mimics how the thermal energy deeper into the tissue which is the primary cooling effect during laser stimulation.
Mentions: During the experiments the subjects were seated in a chair with the dorsum of their left hand and forearm placed flat on a table with the volar forearm perpendicular to the laser beam (Figure 1). The subject and investigator wore protective goggles for the duration of the experiment.

Bottom Line: The laser energy is absorbed by the water content in the most superficial layers of the skin.The simulations were compared to the subjective pain intensity ratings from 16 subjects and to the surface skin temperature distributions measured by an infrared camera.The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajers vej 7D-3, DK 9220 Aalborg, Denmark. ksf@hst.aau.dk

ABSTRACT

Background: CO2 lasers have been used for several decades as an experimental non-touching pain stimulator. The laser energy is absorbed by the water content in the most superficial layers of the skin. The deeper located nociceptors are activated by passive conduction of heat from superficial to deeper skin layers.

Methods: In the current study, a 2D axial finite element model was developed and validated to describe the spatial temperature distribution in the skin after infrared CO2 laser stimulation. The geometry of the model was based on high resolution ultrasound scans. The simulations were compared to the subjective pain intensity ratings from 16 subjects and to the surface skin temperature distributions measured by an infrared camera.

Results: The stimulations were sensed significantly slower and less intense in glabrous skin than they were in hairy skin (MANOVA, p < 0.001). The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, p < 0.001). Of the 16 subjects tested; eight subjects reported pricking pain in the hairy skin following a stimulus of 0.6 J/cm2 (5 W, 0.12 s, d1/e2 = 11.4 mm) only two reported pain to glabrous skin stimulation using the same stimulus intensity. The temperature at the epidermal-dermal junction (depth 50 μm in hairy and depth 133 μm in glabrous skin) was estimated to 46°C for hairy skin stimulation and 39°C for glabrous skin stimulation.

Conclusions: As compared to previous one dimensional heat distribution models, the current two dimensional model provides new possibilities for detailed studies regarding CO2 laser stimulation intensity, temperature levels and nociceptor activation.

Show MeSH
Related in: MedlinePlus