Journal of Biomedical Photonics & Engineering, 2020
Modern studies of the penetration of light into biological tissues is becoming very important in ... more Modern studies of the penetration of light into biological tissues is becoming very important in various medical applications. This is an important factor for determining the optical dose in many diagnostic and therapeutic procedures. The absorption and scattering properties of the tissue under study determine how deeply the light will penetrate into the tissue. However, these optical properties are highly dependent on the wavelength of the light source and tissue condition. This overview paper analyzes the transmission of light through different areas of human and animal head tissues, and the optimal laser wavelength and power density required to reach different parts of the brain are determined using lasers with different wavelengths by comparing the distribution of fluence, penetration depth and the mechanism of interaction between laser light and head tissues. The power variation in different regions of the head is presented, as estimated using Monte Carlo (MC) simulations. Data are analyzed for the absorption and scattering coefficients of the head tissue layers (scalp, skull, brain), calculated using integrating sphere measurements and inverse problem solving algorithms such as inverse MC (IMC) and adding-doubling (IAD). This study not only offered a quantitative comparison between wavelengths in terms of light transmission efficiency, but also anticipated the exciting opportunity for online, accurate and visible optimization of LLLT lighting parameters.
The accurate estimation of skin and skull optical properties over a wide wavelength range of lase... more The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka–Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo ...
I. INTE RNATI O NAL C O NFE R ENCE O F PHYSICS 17 August 2021 Ankara, Turkey, 2021
Transcranial photobiomodulation therapy (PBMT) also known as low-level laser therapy (LLLT) relie... more Transcranial photobiomodulation therapy (PBMT) also known as low-level laser therapy (LLLT) relies on the use of red/NIR light to stimulate, preserve and regenerate cells and tissues. In this review, we will present the most important laser types and sources used in the treatment of the brain, required energy densities to provide treatment, and laser delivery techniques to the brain through the cranium, eye, internal ear, and nostril. Various forms of light therapy have been practiced all over the world for many years. Among them, laser therapy has flourished in recent years. More and more laser equipment is being used in this area. The use of PBMT for neuronal stimulation has been studied in various animal and human models and has been shown to improve cerebral metabolic activity and blood flow and provide neuroprotection through anti-inflammatory and antioxidant pathways. In recent years, the concept of thermotherapy for the treatment of brain tumors has become more widespread. Traditionally, heat therapy is divided into hyperthermia, with a moderate increase in the temperature of the treated tissue above the physiological baseline level, and heat ablation, in which even higher temperatures are reached. Recently, intranasal light therapy, light delivery to the brain through the ear and other channels have become attractive and potential treatments for brain diseases. Here we summarize the various methods of delivering light through the nostrils and ear canals using lasers or light-emitting diodes (LEDs), which can be used alone or in combination with transcranial devices or (applied directly to the scalp) to treat a wide range of brain conditions such as the lungs cognitive impairment, Alzheimer's disease, Parkinson's disease, cerebrovascular disease, depression and anxiety, and insomnia. Evidence shows that low-intensity laser therapy improves blood rheology and cerebral blood flow, so there is no need to pierce blood vessels.
The accurate estimation of skin and skull optical properties over a wide wavelength range of lase... more The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka−Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo simulation was implemented for estimating the optical fluence distribution through a model containing the three tissue layers. The scattering coefficient decreased at longer wavelengths, leading to an increase in optical fluence inside the tissue samples, indicating a higher penetration depth, especially at 980 nm. In general, the obtained results show good agreement with relevant literature.
Optical Technologies for Biology and Medicine, 2022
The knowledge of the optical properties of biological tissues in a wide spectral range is highly ... more The knowledge of the optical properties of biological tissues in a wide spectral range is highly important for the
development of noninvasive diagnostic or treatment procedures. The dispersion coefficient is one of those
properties, from which various information about tissue components can be retrieved. This study is focused on the
measurements of the refractive index of ex vivo cow brain gray matter samples in the visible/near-infrared (NIR)
spectral range at room temperature for characteristic laser wavelengths: 480, 486, 546, 589, 644, 656, 680, 800, 930,
1100, 1300, and 1550 nm. Measurements were performed using the multiwavelength Abbe refractometer. Cow brain
gray matter samples of 0.5 mm thick obtained from ex vivo cow brain were investigated. The specific increment of
the refractive index depending on the temperature of the samples and the Sellmeier coefficients was calculated. The
experimental results allowed us to calculate the cow brain gray matter dispersion with the Cauchy, Conrady, and
Cornu equations. It was observed that all those equations provided good data fitting in the spectral range of the
measurements, but differences were observed outside these limits. We validated the proposed method using distilled
water and the cow brain gray matter ex vivo, and the experimental results were consistent with the reference data.
Modern studies of the penetration of light into biological tissues is becoming very important in ... more Modern studies of the penetration of light into biological tissues is becoming very important in various medical applications. This is an important factor for determining the optical dose in many diagnostic and therapeutic procedures. The absorption and scattering properties of the tissue under study determine how deeply the light will penetrate into the tissue. However, these optical properties are highly dependent on the wavelength of the light source and tissue condition. This overview paper analyzes the transmission of light through different areas of human and animal head tissues, and the optimal laser wavelength and power density required to reach different parts of the brain are determined using lasers with different wavelengths by comparing the distribution of fluence, penetration depth and the mechanism of interaction between laser light and head tissues. The power variation in different regions of the head is presented, as estimated using Monte Carlo (MC) simulations. Data are analyzed for the absorption and scattering coefficients of the head tissue layers (scalp, skull, brain), calculated using integrating sphere measurements and inverse problem solving algorithms such as inverse MC (IMC) and adding-doubling (IAD). This study not only offered a quantitative comparison between wavelengths in terms of light transmission efficiency, but also anticipated the exciting opportunity for online, accurate and visible optimization of LLLT lighting parameters.
The light source-based medical techniques for brain imaging, diagnosis, and treatment are very co... more The light source-based medical techniques for brain imaging, diagnosis, and treatment are very common clinical tools. However, applying these techniques is limited due to the high attenuation of light in the scalp and skull. Such optical attenuation reduces the achievable spatial resolution and precludes the visualization of small features such as brain microvessels. The present study aims to clarify the current methods for providing a desired optical access to the brain with good visualization of the microvessels. The strategy involves the use of transparent cranial implants and optical clearing agents to improve the optical access for laser speckle imaging of cerebral microvasculature. In vivo laser speckle imaging experiments of the mouse, cerebral blood vessels showed that the proposed optical access with combined transmittance of the optically cleared scalp overlying the transparent cranial implant increased signal to noise ratio and image resolution, allowing for visualization...
Journal of Biomedical Photonics & Engineering, 2020
Modern studies of the penetration of light into biological tissues is becoming very important in ... more Modern studies of the penetration of light into biological tissues is becoming very important in various medical applications. This is an important factor for determining the optical dose in many diagnostic and therapeutic procedures. The absorption and scattering properties of the tissue under study determine how deeply the light will penetrate into the tissue. However, these optical properties are highly dependent on the wavelength of the light source and tissue condition. This overview paper analyzes the transmission of light through different areas of human and animal head tissues, and the optimal laser wavelength and power density required to reach different parts of the brain are determined using lasers with different wavelengths by comparing the distribution of fluence, penetration depth and the mechanism of interaction between laser light and head tissues. The power variation in different regions of the head is presented, as estimated using Monte Carlo (MC) simulations. Data are analyzed for the absorption and scattering coefficients of the head tissue layers (scalp, skull, brain), calculated using integrating sphere measurements and inverse problem solving algorithms such as inverse MC (IMC) and adding-doubling (IAD). This study not only offered a quantitative comparison between wavelengths in terms of light transmission efficiency, but also anticipated the exciting opportunity for online, accurate and visible optimization of LLLT lighting parameters.
The accurate estimation of skin and skull optical properties over a wide wavelength range of lase... more The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka–Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo ...
I. INTE RNATI O NAL C O NFE R ENCE O F PHYSICS 17 August 2021 Ankara, Turkey, 2021
Transcranial photobiomodulation therapy (PBMT) also known as low-level laser therapy (LLLT) relie... more Transcranial photobiomodulation therapy (PBMT) also known as low-level laser therapy (LLLT) relies on the use of red/NIR light to stimulate, preserve and regenerate cells and tissues. In this review, we will present the most important laser types and sources used in the treatment of the brain, required energy densities to provide treatment, and laser delivery techniques to the brain through the cranium, eye, internal ear, and nostril. Various forms of light therapy have been practiced all over the world for many years. Among them, laser therapy has flourished in recent years. More and more laser equipment is being used in this area. The use of PBMT for neuronal stimulation has been studied in various animal and human models and has been shown to improve cerebral metabolic activity and blood flow and provide neuroprotection through anti-inflammatory and antioxidant pathways. In recent years, the concept of thermotherapy for the treatment of brain tumors has become more widespread. Traditionally, heat therapy is divided into hyperthermia, with a moderate increase in the temperature of the treated tissue above the physiological baseline level, and heat ablation, in which even higher temperatures are reached. Recently, intranasal light therapy, light delivery to the brain through the ear and other channels have become attractive and potential treatments for brain diseases. Here we summarize the various methods of delivering light through the nostrils and ear canals using lasers or light-emitting diodes (LEDs), which can be used alone or in combination with transcranial devices or (applied directly to the scalp) to treat a wide range of brain conditions such as the lungs cognitive impairment, Alzheimer's disease, Parkinson's disease, cerebrovascular disease, depression and anxiety, and insomnia. Evidence shows that low-intensity laser therapy improves blood rheology and cerebral blood flow, so there is no need to pierce blood vessels.
The accurate estimation of skin and skull optical properties over a wide wavelength range of lase... more The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka−Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo simulation was implemented for estimating the optical fluence distribution through a model containing the three tissue layers. The scattering coefficient decreased at longer wavelengths, leading to an increase in optical fluence inside the tissue samples, indicating a higher penetration depth, especially at 980 nm. In general, the obtained results show good agreement with relevant literature.
Optical Technologies for Biology and Medicine, 2022
The knowledge of the optical properties of biological tissues in a wide spectral range is highly ... more The knowledge of the optical properties of biological tissues in a wide spectral range is highly important for the
development of noninvasive diagnostic or treatment procedures. The dispersion coefficient is one of those
properties, from which various information about tissue components can be retrieved. This study is focused on the
measurements of the refractive index of ex vivo cow brain gray matter samples in the visible/near-infrared (NIR)
spectral range at room temperature for characteristic laser wavelengths: 480, 486, 546, 589, 644, 656, 680, 800, 930,
1100, 1300, and 1550 nm. Measurements were performed using the multiwavelength Abbe refractometer. Cow brain
gray matter samples of 0.5 mm thick obtained from ex vivo cow brain were investigated. The specific increment of
the refractive index depending on the temperature of the samples and the Sellmeier coefficients was calculated. The
experimental results allowed us to calculate the cow brain gray matter dispersion with the Cauchy, Conrady, and
Cornu equations. It was observed that all those equations provided good data fitting in the spectral range of the
measurements, but differences were observed outside these limits. We validated the proposed method using distilled
water and the cow brain gray matter ex vivo, and the experimental results were consistent with the reference data.
Modern studies of the penetration of light into biological tissues is becoming very important in ... more Modern studies of the penetration of light into biological tissues is becoming very important in various medical applications. This is an important factor for determining the optical dose in many diagnostic and therapeutic procedures. The absorption and scattering properties of the tissue under study determine how deeply the light will penetrate into the tissue. However, these optical properties are highly dependent on the wavelength of the light source and tissue condition. This overview paper analyzes the transmission of light through different areas of human and animal head tissues, and the optimal laser wavelength and power density required to reach different parts of the brain are determined using lasers with different wavelengths by comparing the distribution of fluence, penetration depth and the mechanism of interaction between laser light and head tissues. The power variation in different regions of the head is presented, as estimated using Monte Carlo (MC) simulations. Data are analyzed for the absorption and scattering coefficients of the head tissue layers (scalp, skull, brain), calculated using integrating sphere measurements and inverse problem solving algorithms such as inverse MC (IMC) and adding-doubling (IAD). This study not only offered a quantitative comparison between wavelengths in terms of light transmission efficiency, but also anticipated the exciting opportunity for online, accurate and visible optimization of LLLT lighting parameters.
The light source-based medical techniques for brain imaging, diagnosis, and treatment are very co... more The light source-based medical techniques for brain imaging, diagnosis, and treatment are very common clinical tools. However, applying these techniques is limited due to the high attenuation of light in the scalp and skull. Such optical attenuation reduces the achievable spatial resolution and precludes the visualization of small features such as brain microvessels. The present study aims to clarify the current methods for providing a desired optical access to the brain with good visualization of the microvessels. The strategy involves the use of transparent cranial implants and optical clearing agents to improve the optical access for laser speckle imaging of cerebral microvasculature. In vivo laser speckle imaging experiments of the mouse, cerebral blood vessels showed that the proposed optical access with combined transmittance of the optically cleared scalp overlying the transparent cranial implant increased signal to noise ratio and image resolution, allowing for visualization...
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Papers by alaa shanshool
development of noninvasive diagnostic or treatment procedures. The dispersion coefficient is one of those
properties, from which various information about tissue components can be retrieved. This study is focused on the
measurements of the refractive index of ex vivo cow brain gray matter samples in the visible/near-infrared (NIR)
spectral range at room temperature for characteristic laser wavelengths: 480, 486, 546, 589, 644, 656, 680, 800, 930,
1100, 1300, and 1550 nm. Measurements were performed using the multiwavelength Abbe refractometer. Cow brain
gray matter samples of 0.5 mm thick obtained from ex vivo cow brain were investigated. The specific increment of
the refractive index depending on the temperature of the samples and the Sellmeier coefficients was calculated. The
experimental results allowed us to calculate the cow brain gray matter dispersion with the Cauchy, Conrady, and
Cornu equations. It was observed that all those equations provided good data fitting in the spectral range of the
measurements, but differences were observed outside these limits. We validated the proposed method using distilled
water and the cow brain gray matter ex vivo, and the experimental results were consistent with the reference data.
development of noninvasive diagnostic or treatment procedures. The dispersion coefficient is one of those
properties, from which various information about tissue components can be retrieved. This study is focused on the
measurements of the refractive index of ex vivo cow brain gray matter samples in the visible/near-infrared (NIR)
spectral range at room temperature for characteristic laser wavelengths: 480, 486, 546, 589, 644, 656, 680, 800, 930,
1100, 1300, and 1550 nm. Measurements were performed using the multiwavelength Abbe refractometer. Cow brain
gray matter samples of 0.5 mm thick obtained from ex vivo cow brain were investigated. The specific increment of
the refractive index depending on the temperature of the samples and the Sellmeier coefficients was calculated. The
experimental results allowed us to calculate the cow brain gray matter dispersion with the Cauchy, Conrady, and
Cornu equations. It was observed that all those equations provided good data fitting in the spectral range of the
measurements, but differences were observed outside these limits. We validated the proposed method using distilled
water and the cow brain gray matter ex vivo, and the experimental results were consistent with the reference data.