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Thermal effects of laser illumination in GASMAS for lung monitoring - A clinical study on skin heating

von der Sahle, Sophie Helene LU (2025) PHYM03 20251
Department of Physics
Atomic Physics
Abstract
Gas in Scattering Media Absorption Spectroscopy (GASMAS) is a near-infrared (IR) optical spectroscopy technique showing great potential in the continuous, non-invasive monitoring of the lungs. While the feasibility of GASMAS has been proven in neonatal lung studies, applying the technique to older children and adults is challenging. The increased tissue thickness strongly attenuates the signal, necessitating higher laser intensities potentially causing heating damage. Though GASMAS as well as various other medical techniques employ near-IR light, research on the thermal effects of this type of radiation on human tissue remains limited. This study investigates the induced skin heating due to 764 nm near-infrared laser light through a... (More)
Gas in Scattering Media Absorption Spectroscopy (GASMAS) is a near-infrared (IR) optical spectroscopy technique showing great potential in the continuous, non-invasive monitoring of the lungs. While the feasibility of GASMAS has been proven in neonatal lung studies, applying the technique to older children and adults is challenging. The increased tissue thickness strongly attenuates the signal, necessitating higher laser intensities potentially causing heating damage. Though GASMAS as well as various other medical techniques employ near-IR light, research on the thermal effects of this type of radiation on human tissue remains limited. This study investigates the induced skin heating due to 764 nm near-infrared laser light through a clinical study involving 25 subjects with varying skin types. Measurements were conducted using both a free beam setup and an optical probe with a diffuser. The skin temperature increase was measured under different light intensities and correlations with physiological factors such as skin type and melanin content were investigated. The free beam measurements clearly showed increased skin heating the darker the skin gets, consistent with higher melanin absorption. The probe measurements, however, displayed no consistent trend, indicating further influencing factors. These findings provide a quantitative basis for defining safe usage parameters for the exposure to near-IR laser light and highlight the need for further studies across a broader range of skin tones. (Less)
Popular Abstract
Modern healthcare increasingly turns to non-invasive technologies improving patient comfort and enabling safer diagnostics, monitoring and treatment methods. Imagine, for example, to check how your lungs are doing - without any X-rays or discomfort. That is the idea behind one such technique called GASMAS, short for Gas Absorption in Scattering Media Spectroscopy. It uses a near-infrared laser light to continuously monitor the oxygen concentration in the lungs, without harmful radiation or invasive procedures.
Research has shown that GASMAS works to monitor the lungs of newborn babies. But there is a catch when wanting to use it for older children and adults. Bigger bodies mean the light has to travel through more tissue, requiring higher... (More)
Modern healthcare increasingly turns to non-invasive technologies improving patient comfort and enabling safer diagnostics, monitoring and treatment methods. Imagine, for example, to check how your lungs are doing - without any X-rays or discomfort. That is the idea behind one such technique called GASMAS, short for Gas Absorption in Scattering Media Spectroscopy. It uses a near-infrared laser light to continuously monitor the oxygen concentration in the lungs, without harmful radiation or invasive procedures.
Research has shown that GASMAS works to monitor the lungs of newborn babies. But there is a catch when wanting to use it for older children and adults. Bigger bodies mean the light has to travel through more tissue, requiring higher laser powers. This raises concerns about unwanted skin heating - a problem that is not yet understood. In fact, although near-IR light is being used more and more in medical technologies, very little research has been done to investigate its effects on human skin, no less of different skin tones.
To make sure this type of light is safe, a clinical study was conducted on 25 volunteers of varying skin types. The study measured the increase in skin temperature when being exposed to 764 nm near-IR laser light, a typical wavelength in GASMAS for lung monitoring. The skin was illuminated using two different methods: one where the laser beam was shone directly onto the skin and another where the light was spread out through a diffuser attached to the skin. The study also looked at whether and how the skin type and the melanin content - the pigment that gives the skin its colour - relate to how much the skin heats up.
The results showed that the darker the skin, meaning the higher the melanin content in the skin, the more the skin heated up when exposed to the direct laser beam. However, when the light was applied through the diffuser, the results were less clear, suggesting that other factors may influence the skin’s response. These findings provide a foundation for assessing safety limits when using near-IR light, though further research is needed.
If technologies like GASMAS are to be used safely on all patients, a clear understanding of how different skin types respond to near-IR light is essential. This study is a first step towards that goal - helping to ensure promising medical technologies are not only effective, but safe for everyone. (Less)
Please use this url to cite or link to this publication:
author
von der Sahle, Sophie Helene LU
supervisor
organization
course
PHYM03 20251
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Diode laser, optical spectroscopy, tissue temperature increase, in-vivo, dermal probe, free beam, laser safety, skin type
language
English
id
9211527
date added to LUP
2025-09-24 08:10:49
date last changed
2025-09-24 08:10:49
@misc{9211527,
  abstract     = {{Gas in Scattering Media Absorption Spectroscopy (GASMAS) is a near-infrared (IR) optical spectroscopy technique showing great potential in the continuous, non-invasive monitoring of the lungs. While the feasibility of GASMAS has been proven in neonatal lung studies, applying the technique to older children and adults is challenging. The increased tissue thickness strongly attenuates the signal, necessitating higher laser intensities potentially causing heating damage. Though GASMAS as well as various other medical techniques employ near-IR light, research on the thermal effects of this type of radiation on human tissue remains limited. This study investigates the induced skin heating due to 764 nm near-infrared laser light through a clinical study involving 25 subjects with varying skin types. Measurements were conducted using both a free beam setup and an optical probe with a diffuser. The skin temperature increase was measured under different light intensities and correlations with physiological factors such as skin type and melanin content were investigated. The free beam measurements clearly showed increased skin heating the darker the skin gets, consistent with higher melanin absorption. The probe measurements, however, displayed no consistent trend, indicating further influencing factors. These findings provide a quantitative basis for defining safe usage parameters for the exposure to near-IR laser light and highlight the need for further studies across a broader range of skin tones.}},
  author       = {{von der Sahle, Sophie Helene}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Thermal effects of laser illumination in GASMAS for lung monitoring - A clinical study on skin heating}},
  year         = {{2025}},
}