A new perspective on delivery of red-near-infrared light therapy for disorders of the brain

Nathan S. Hart, Melinda Fitzgerald

    Research output: Contribution to journalArticle

    5 Citations (Scopus)

    Abstract

    © 2016, Discovery Medicine. All Rights Reserved.
    Red-near-infrared light has been used for a range of therapeutic purposes. However, clinical trials of near-infrared laser light for treatment of stroke were abandoned after failing interim futility analyses. Lack of efficacy has been attributed to sub-optimal treatment parameters and low penetrance of light to affected brain regions. Here, we assess penetrance of wavelengths from 450-880 nm in human post-mortem samples, and demonstrate that human skin, skull bone and brain transmits therapeutically relevant quantities of light from external sources at wavelengths above 600 nm. Transmission through post-mortem skull bone was dependent upon thickness, and ranged from 5-12% at peak wavelengths of 700-850 nm. Transmission through brain tissue ranged from 1-7%, following an approximately linear relationship between absorbance and tissue thickness. Importantly, natural sunlight encompasses the wavelengths used in red-near-infrared light therapy. Calculations of the average irradiance of light delivered by sunlight demonstrate that sunlight can provide doses of light equivalent to - and in some cases greater than - those used in therapeutic trials. Natural sunlight could, therefore, be used as a source of therapeutic red-near-infrared light, but equally its contribution must be considered when assessing and controlling therapeutic dose in patients. For targets deep within the brain, it is unlikely that sufficient doses of light can be delivered trans-cranially; therapeutic light must be supplied via optical fibers or implanted light sources.
    Original languageEnglish
    Number of pages1
    JournalDiscovery Medicine
    Volume22
    Issue number120
    Publication statusPublished - 19 Sep 2016

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    Phototherapy
    Brain Diseases
    Light
    Sunlight
    Penetrance
    Brain
    Skull
    Therapeutics
    Medical Futility
    Optical Fibers
    Bone and Bones
    Lasers
    Stroke
    Medicine
    Clinical Trials
    Skin

    Cite this

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    title = "A new perspective on delivery of red-near-infrared light therapy for disorders of the brain",
    abstract = "{\circledC} 2016, Discovery Medicine. All Rights Reserved.Red-near-infrared light has been used for a range of therapeutic purposes. However, clinical trials of near-infrared laser light for treatment of stroke were abandoned after failing interim futility analyses. Lack of efficacy has been attributed to sub-optimal treatment parameters and low penetrance of light to affected brain regions. Here, we assess penetrance of wavelengths from 450-880 nm in human post-mortem samples, and demonstrate that human skin, skull bone and brain transmits therapeutically relevant quantities of light from external sources at wavelengths above 600 nm. Transmission through post-mortem skull bone was dependent upon thickness, and ranged from 5-12{\%} at peak wavelengths of 700-850 nm. Transmission through brain tissue ranged from 1-7{\%}, following an approximately linear relationship between absorbance and tissue thickness. Importantly, natural sunlight encompasses the wavelengths used in red-near-infrared light therapy. Calculations of the average irradiance of light delivered by sunlight demonstrate that sunlight can provide doses of light equivalent to - and in some cases greater than - those used in therapeutic trials. Natural sunlight could, therefore, be used as a source of therapeutic red-near-infrared light, but equally its contribution must be considered when assessing and controlling therapeutic dose in patients. For targets deep within the brain, it is unlikely that sufficient doses of light can be delivered trans-cranially; therapeutic light must be supplied via optical fibers or implanted light sources.",
    author = "Hart, {Nathan S.} and Melinda Fitzgerald",
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    A new perspective on delivery of red-near-infrared light therapy for disorders of the brain. / Hart, Nathan S.; Fitzgerald, Melinda.

    In: Discovery Medicine, Vol. 22, No. 120, 19.09.2016.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - A new perspective on delivery of red-near-infrared light therapy for disorders of the brain

    AU - Hart, Nathan S.

    AU - Fitzgerald, Melinda

    PY - 2016/9/19

    Y1 - 2016/9/19

    N2 - © 2016, Discovery Medicine. All Rights Reserved.Red-near-infrared light has been used for a range of therapeutic purposes. However, clinical trials of near-infrared laser light for treatment of stroke were abandoned after failing interim futility analyses. Lack of efficacy has been attributed to sub-optimal treatment parameters and low penetrance of light to affected brain regions. Here, we assess penetrance of wavelengths from 450-880 nm in human post-mortem samples, and demonstrate that human skin, skull bone and brain transmits therapeutically relevant quantities of light from external sources at wavelengths above 600 nm. Transmission through post-mortem skull bone was dependent upon thickness, and ranged from 5-12% at peak wavelengths of 700-850 nm. Transmission through brain tissue ranged from 1-7%, following an approximately linear relationship between absorbance and tissue thickness. Importantly, natural sunlight encompasses the wavelengths used in red-near-infrared light therapy. Calculations of the average irradiance of light delivered by sunlight demonstrate that sunlight can provide doses of light equivalent to - and in some cases greater than - those used in therapeutic trials. Natural sunlight could, therefore, be used as a source of therapeutic red-near-infrared light, but equally its contribution must be considered when assessing and controlling therapeutic dose in patients. For targets deep within the brain, it is unlikely that sufficient doses of light can be delivered trans-cranially; therapeutic light must be supplied via optical fibers or implanted light sources.

    AB - © 2016, Discovery Medicine. All Rights Reserved.Red-near-infrared light has been used for a range of therapeutic purposes. However, clinical trials of near-infrared laser light for treatment of stroke were abandoned after failing interim futility analyses. Lack of efficacy has been attributed to sub-optimal treatment parameters and low penetrance of light to affected brain regions. Here, we assess penetrance of wavelengths from 450-880 nm in human post-mortem samples, and demonstrate that human skin, skull bone and brain transmits therapeutically relevant quantities of light from external sources at wavelengths above 600 nm. Transmission through post-mortem skull bone was dependent upon thickness, and ranged from 5-12% at peak wavelengths of 700-850 nm. Transmission through brain tissue ranged from 1-7%, following an approximately linear relationship between absorbance and tissue thickness. Importantly, natural sunlight encompasses the wavelengths used in red-near-infrared light therapy. Calculations of the average irradiance of light delivered by sunlight demonstrate that sunlight can provide doses of light equivalent to - and in some cases greater than - those used in therapeutic trials. Natural sunlight could, therefore, be used as a source of therapeutic red-near-infrared light, but equally its contribution must be considered when assessing and controlling therapeutic dose in patients. For targets deep within the brain, it is unlikely that sufficient doses of light can be delivered trans-cranially; therapeutic light must be supplied via optical fibers or implanted light sources.

    M3 - Article

    VL - 22

    JO - Discovery Medicine

    JF - Discovery Medicine

    SN - 1539-6509

    IS - 120

    ER -