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Cited by 72Optical Imaging and Spectroscopy TechniquesNon-Invasive Vital Sign MonitoringSpectroscopy Techniques in Biomedical and Chemical Research

Effect of skin color on optical properties and the implications for medical optical technologies: a review

Open access
Setchfield, Kerry, Gorman, Alistair, Simpson, A. Hamish R. W., Somekh, Michael G., Wright, Amanda J.·2024·Journal of Biomedical Optics
DOI 10.1117/1.jbo.29.1.010901PMC PMC10807857
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Abstract

SignificanceSkin color affects light penetration leading to differences in its absorption and scattering properties. COVID-19 highlighted the importance of understanding of the interaction of light with different skin types, e.g., pulse oximetry (PO) unreliably determined oxygen saturation levels in people from Black and ethnic minority backgrounds. Furthermore, with increased use of other medical wearables using light to provide disease information and photodynamic therapies to treat skin cancers, a thorough understanding of the effect skin color has on light is important for reducing healthcare disparities.AimThe aim of this work is to perform a thorough review on the effect of skin color on optical properties and the implication of variation on optical medical technologies.ApproachPublished in vivo optical coefficients associated with different skin colors were collated and their effects on optical penetration depth and transport mean free path (TMFP) assessed.ResultsVariation among reported values is significant. We show that absorption coefficients for dark skin are ∼6% to 74% greater than for light skin in the 400 to 1000 nm spectrum. Beyond 600 nm, the TMFP for light skin is greater than for dark skin. Maximum transmission for all skin types was beyond 940 nm in this spectrum. There are significant losses of light with increasing skin depth; in this spectrum, depending upon Fitzpatrick skin type (FST), on average 14% to 18% of light is lost by a depth of 0.1 mm compared with 90% to 97% of the remaining light being lost by a depth of 1.93 mm.ConclusionsCurrent published data suggest that at wavelengths beyond 940 nm light transmission is greatest for all FSTs. Data beyond 1000 nm are minimal and further study is required. It is possible that the amount of light transmitted through skin for all skin colors will converge with increasing wavelength enabling optical medical technologies to become independent of skin color.

AI snapshot

Written from the paper’s full text.

TL;DR

This review collates published in vivo optical coefficients by Fitzpatrick skin type (FST) and assesses how skin color affects light penetration, transport mean free path (TMFP), and transmission. It finds dark skin generally has higher absorption and lower transmission in the visible/NIR, while transmission is greatest beyond 940 nm for all FSTs, with implications for OCT, PDT, and pulse oximetry/wearables.

Key findings

  • Absorption coefficients for FST V–VI are ∼7% to 74% greater than FST I–II in the 400 to 1000 nm spectrum, with the smallest difference at 440 nm (6.5%) and largest at 640 nm (74.4%).
  • Beyond 600 nm, TMFP is greater for light skin than dark skin; maximum TMFP was 1.37 mm for FST I–II at 980 to 1000 nm, 1.27 mm for FST III–IV at 1470 nm, and 0.83 mm for FST V–VI at 940 nm. Between 960 and 1000 nm, TMFP was ∼90% greater for FST I–II than darker FSTs.
  • Maximum transmission beyond 0.1 mm was 92.6% at 1000 nm for FST I–II, 88.7% at 1290 nm for FST III–IV, and 88.2% at 940 nm for FST V–VI. By 1.93 mm, on average 91%, 97%, and 96% of remaining light was lost for FST I–II, III–IV, and V–VI, respectively.
  • Published data are limited: of 20 publications reporting in vivo absorption and reduced scattering coefficients, only 12 state FST; 7 measure FST I–II, 7 measure FST III–IV, and 3 measure FST V–VI, with sample numbers from 1 to 1734 and a modal sample number of 6. Beyond 1000 nm, measurements were available only for FST III–IV.

Methods

  • Literature review collating published in vivo absorption and reduced scattering coefficients associated with different skin colors/FST; data from 12 papers stating FST were pooled into FST I–II, III–IV, and V–VI groupings.
  • The review assessed optical penetration depth and TMFP, and calculated percentage transmission using averaged published coefficients with the expression Iout=Iin e−(μa+μs′)l.
  • Three case studies examined implications for optical coherence tomography (OCT), photodynamic therapy (PDT), and medical wearables with a focus on pulse oximetry (PO).

Limitations

  • The paper states that published data show high inter- and intrapublication variability, limited data for FST V–VI, minimal data beyond 1000 nm, and that FST determination is subjective and unreliable for darker skin. It also notes that the transmission expression is “somewhat ad hoc” and tends to overestimate light reaching a given position, and that TMFP does not consider absorption.
  • The text makes evident that averaging heterogeneous data across different measurement methods, locations, wavelength ranges, and small samples may obscure differences; some visible-spectrum conclusions are based on a single publication and one subject, and the applicability of pooled data to more melanized skin is questioned.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1117/1.jbo.29.1.010901

Cites

137 of 137 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 142 cited sources checked · 0 supported · 0 flagged

  • Findingcitation

    At 600 nm, absorption data published by Bosschaart et al. are progressively greater with increasing skin pigmentation than Tseng et al.'s data, being 25%, 45%, and 77% greater for FST I-II, III-IV, and V-VI, respectively.

    “At 600 nm, absorption data published by Bosschaart et al.42 are progressively greater with increasing skin pigmentation than Tseng et al.’s41 data, being 25%, 45%, and 77% greater for FST I–II, III–IV, and V–VI, respectively.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [42] source

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    • cites [41] source

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  • Findingown data

    Average differences between the maximum and minimum reported absorption coefficients were 81%, 51%, and 38% for FST I-II, III-V, and V-VI, respectively.

    “Average differences between the maximum and minimum reported absorption coefficients were 81%, 51%, and 38% for FST I–II, III–V, and V–VI, respectively.”
    Quote in the paperSubstantial claim
  • Findingown data

    The review identified 20 publications that report the in vivo absorption and reduced scattering coefficients of the skin.

    “We identified 20 publications that report the in vivo absorption and reduced scattering coefficients of the skin.”
    Quote in the paperSubstantial claim
  • Findingown data

    Variability between published data within each FST group at a given wavelength is huge, with the average difference between the maximum and minimum reduced scattering coefficients across measured wavelengths being 98%, 25%, and 31% for FST I-II, III-V, and V-VI, respectively.

    “Variability between the published data within each FST group at given wavelength is huge with the average difference between the maximum and minimum reduced scattering coefficients across the measured wavelengths being 98%, 25%, and 31% for FST I–II, III–V, and V–VI, respectively.”
    Quote in the paperSubstantial claim
  • Findingnone given

    The average TMFP across each FST of photons travelling through the skin ranges from 0.68 to 0.81 mm across the measurement spectrum depending upon FST.

    “The average TMFP across each FST of photons travelling through the skin ranges from 0.68 to 0.81 mm across the measurement spectrum depending upon FST.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.
  • May combine two claims. 74
  • Classified as probably not a substantial claim. 20
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data

    Of the 20 papers reporting original measured data, only 12 state the FST; of these, 7 measure optical properties for FST I-II, 7 for FST III-IV, and 3 for FST V-VI.

    “Of the 20 papers reporting the original measured data, only 12 state the FST and of these 7 measure optical properties for FST I–II, 7 measure FST III–IV, and 3 measure FST V–VI.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Sample numbers for each study vary widely from 1 to 1734, with the modal sample number being 6.

    “Sample numbers for each study vary widely from 1 to 1734, with the modal sample number being 6.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Beyond 600 nm, there was a tendency toward convergence of the reduced scattering coefficients for FSTs III-IV and V-VI, and between 600 to 1000 nm the reduced scattering coefficients associated with FST I-II were 22% to 48% less than for the darker FSTs.

    “Beyond 600 nm, there was a tendency toward convergence of the reduced scattering coefficients for FSTs III–IV and V–VI and between 600 to 1000 nm the reduced scattering coefficients associated with FST I–II were 22% to 48% less than for the darker FSTs.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Findingown data

    Using the published data, the average TMFP is least in FST V-VI samples and greatest in FST III-IV in the 400 to 1000 nm spectrum.

    “Using the published data, the average TMFP is least in FST V–VI samples and greatest in FST III–IV in the 400 to 1000 nm spectrum.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Findingreasoning

    The data suggest that there are fewer scattering events in more melanized skin types at visible wavelengths (400 to 600 nm), where the reduced scattering coefficients for FST V-VI were up to twofold less than for FST I-II.

    “The data suggest that there are fewer scattering events in more melanized skin types at visible wavelengths (400 to 600 nm), where the reduced scattering coefficients for FST V–VI were up to twofold less than for FST I–II.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Findingreasoning

    Because scattering is least for all FSTs at wavelengths beyond 940 nm, transmission is greatest in this spectrum.

    “Despite the increasing absorption observed beyond 940 nm (described in Sec. 3.2), because scattering is least for all FSTs at these wavelengths, transmission is greatest in this spectrum.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The maximum amount of light transmitted beyond 0.1 mm is 92.6% at 1000 nm, 88.7% at 1290 nm, and 88.2% at 940 nm for FST I-II, III-IV, and V-VI, respectively.

    “The maximum amount of light transmitted beyond 0.1 mm is 92.6% at 1000 nm, 88.7% at 1290 nm, and 88.2% at 940 nm for FST I–II, III–IV, and V–VI, respectively.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The expression Iout=Iin e−(μa+μs′)l is an ad hoc expression that will tend to overestimate the amount of light reaching a particular position.
    • The authors state this as an assumption: The light available at a certain depth to form a focus has suffered far less scattering than a typical photon.

  • May combine two claims.

    Findingreasoning

    Across the 400 to 1000 nm spectrum, on average ∼14% of light is lost at a depth of 0.1 mm in FST I-II and by a depth of 1.93 mm 91% of the remaining light has been lost.

    “across the 400 to 1000 nm spectrum on average ∼14% of light is lost at a depth of 0.1 mm in FST I–II and by a depth of 1.93 mm 91% of the remaining light has been lost.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the NIR, absorption coefficients start to converge but tend to increase in value with increasing wavelength.

    “In the NIR absorption, coefficients start to converge but tend to increase in value with increasing wavelength.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Findingown data

    Beyond 600 nm, the depth at which an image could potentially be formed increases with increasing wavelength and is greatest for FST I-II at 980 to 1000 nm being 1.37 mm, for FST III-IV at 1470 nm being 1.27 mm, and for FST V-VI at 940 nm being 0.83 mm.

    “The results gathered from the published data and analyzed here suggest that beyond 600 nm the depth at which an image could potentially be formed increases with increasing wavelength and is greatest for FST I–II at 980 to 1000 nm being 1.37 mm, for FST III–IV at 1470 nm being 1.27 mm, and for FST V–VI at 940 nm being 0.83 mm.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Findingown data

    FST V-VI absorption coefficients are ∼7% to 74% greater than those for FST I-II in the 400 to 1000 nm spectrum, with the difference being least at 440 nm (6.5%) and greatest at 640 nm (74.4%).

    “FST V–VI absorption coefficients are ∼7% to 74% greater than those for FST I–II in the 400 to 1000 nm spectrum, the difference being least at 440 nm (6.5%) and greatest at 640 nm (74.4%).”
    • Also stated in: § Results · plain
      “We show that absorption coefficients for dark skin are ∼6% to 74% greater than for light skin in the 400 to 1000 nm spectrum.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Findingcitation

    At 500 nm, Bosschaart et al.'s data are 73% and 77% greater than Tseng et al.'s for FST I-II and III-IV, respectively.

    “At 500 nm, the differences are more marked, with Bosschaart et al.’s42 data being 73% and 77% greater than Tseng et al.’s41 for FST I–II and III–IV, respectively.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [42] source

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    • cites [41] source

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  • May combine two claims.

    Findingown data

    The published data plotted in Fig. 4 suggest that absorption is generally greater for FST III-IV than I-II in the 400 to 450 nm spectrum, and in this region absorption by FST V-VI is less than for either of the lighter skin type groups.

    “The published data plotted in Fig. 4 suggest that absorption is generally greater for FST III–IV than I–II in the 400 to 450 nm spectrum, and in this region absorption by FST V–VI is less than for either of the lighter skin type groups (i.e. FST I-II and III-IV).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    At 940 nm and a skin depth of 1.93 mm, light transmission has reduced to between 18% and 23% in FST I-II, between 8% and 9% in FST III-IV, and between 6% and 9% in FST V-VI.

    “At this wavelength and a skin depth of 1.93 mm, light transmission has reduced to between 18% and 23% in FST I–II compared with between 8% and 9%, and between 6% and 9% in FST III–IV and V–VI, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In FST III-IV and V-VI skin, average losses are 18% and 16%, respectively, at 0.1 mm and 97% and 96%, respectively, by a depth of 1.93 mm.

    “In FST III–IV and V–VI skin, these losses are on average 18% and 16%, respectively, at 0.1 mm and 97% and 96%, respectively, by a depth of 1.93 mm.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    For FST III-IV beyond 1000 nm, less light is lost than in the 400 to 1000 nm spectrum, with 12% average losses at a depth of 0.1 mm and 92% by a depth of 1.93 mm.

    “For FST III–IV beyond 1000 nm less light is lost than in the 400 to 1000 nm spectrum, with 12% average losses at a depth of 0.1 mm and 92% by a depth of 1.93 mm.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    At 940 nm, light is still travelling predominantly in the forward direction at a depth of 0.1 mm and is at ∼88% on average of its original intensity for all FSTs.

    “At 940 nm, light is still travelling predominantly in the forward direction (as shown by TMFP calculations) at a depth of 0.1 mm and is at ∼88% on average of its original intensity for all FSTs.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    The minimal transmission reported for each FST in the visible wavelength range was 78.9% for FST V-VI (at 450 nm), 71.2% for FST I-II (at 420 nm), and 69.2% for FST III-IV (at 420 nm).

    “the minimal transmission reported for each FST in the visible wavelength range being 78.9% for FST V–VI (at 450 nm) compared with 71.2% for FST I–II (at 420 nm) and 69.2% for FST III–IV (at 420 nm).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    The majority of studies on OCT imaging of AK do not mention skin color, likely due to the perception that AK only affects people with light skin.

    “the majority of studies do not mention skin color and this is likely due to the perception that AK only affects people with light skin.99–104”
    Quote in the paperSubstantial claim0 of 6 sources checked
    • cites [99] source

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    • cites [104] source

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  • May combine two claims.

    Findingreasoning

    Losses are wavelength dependent as well as FST dependent.

    “However, losses are wavelength dependent as well as FST dependent”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The effect of skin color on OCT has rarely been discussed, making it difficult to draw conclusions.

    “The effect of skin color on OCT has rarely been discussed making it difficult to draw conclusions.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Both Doornbos et al. and Meglinski and Matcher present optical coefficients for FST I-II skin.

    “Both of these publications present optical coefficients for FST I–II skin.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [38] source

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    • cites [43] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingnone given

    Data used in this review were collated from 12 publications, which have been cited between 5 and 673 times.

    “Data used in this review were collated from 12 publications, which have been cited between 5 and 673 times.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    The three publications representing FST V-VI used in this review also presented data relating to the lighter skin types and the total sample numbers for darker skin were less than for light skin among these publications.

    “It should be noted that the three publications representing FST V–VI used in this review also presented data relating to the lighter skin types and the total sample numbers for darker skin were less than for light skin among these publications.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Publications describing the optical properties of only FST V-VI skin have been cited least in total, with an average of 121 citations per publication compared with an average of 296 citations per publication for FST I-II.

    “Publications describing the optical properties of only FST V–VI skin have been cited least in total, with an average of 121 citations per publication compared with an average of 296 citations per publication for FST I–II.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Publications by Doornbos et al. and Meglinski and Matcher were the most cited with 673 and 544 citations, respectively.

    “Publications by Doornbos et al.38 and Meglinski and Matcher43 were the most cited with 673 and 544 citations, respectively.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [38] source

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    • cites [43] source

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  • May combine two claims.

    Findingcitation

    The publications used for this review that reported optical properties of light skin tones tended to be less recent, which might represent social changes and affect downstream uses of these properties.

    “The publications used for this review that reported optical properties of light skin tones tended to be less recent, which might represent social changes and affect downstream uses of these properties.148”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [148] O’Brien, 2022

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  • May combine two claims.

    Findingown data

    Published data beyond 1000 nm are minimal and not equivalently representative of all FSTs.

    “there is limited data beyond 1000 nm”
    • Also stated in: § Conclusions · plain
      “Because the published data beyond 1000 nm are minimal and not equivalently representative of all FSTs conclusions are difficult to draw.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Melanosomes in more pigmented skin types tend to be larger (~1 μm) and dispersed singly, whereas melanosomes in less pigmented skin tend to be aggregated and smaller (~0.5 μm).

    “Melanosomes in more pigmented skin types tend to be larger (∼1 μm) and dispersed singly, whereas the melanosomes in less pigmented skin tend to be aggregated and smaller (∼0.5 μm).34”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [34] source

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  • May combine two claims.

    Premisecitation

    Pulse oximetry consistently overestimated oxygen saturation, and this overestimation was particularly significant for darker skin.

    “It showed that PO, which is used to measure oxygen saturation in the blood, consistently overestimated oxygen levels, and this was particularly significant for darker skin.”
    • Also stated in: § Significance · plain
      “pulse oximetry (PO) unreliably determined oxygen saturation levels in people from Black and ethnic minority backgrounds.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [11] source

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  • May combine two claims.

    Premisecitation

    More highly pigmented skin has more melanosomes and a greater ability to transfer melanin.

    “All skin types tend to have the same numbers of melanocytes but the numbers of melanosomes within each and their ability to pass these on to keratinocytes is varied, with more highly pigmented skin having more melanosomes and a greater ability to transfer melanin.33”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [33] source

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  • May combine two claims.

    Premisecitation

    The penetration depth of light for imaging purposes and the results from medical wearable devices are affected by skin color.

    “the penetration depth of light for imaging purposes and the results from medical wearable devices are affected by skin color.7–10”
    Quote in the paperSubstantial claim0 of 4 sources checked
    • cites [7] source

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  • May combine two claims.

    Premisecitation

    The Fitzpatrick skin type scale is unreliable for darker skin, does not take into account skin color ranges, and does not accurately provide skin cancer risk, leading to healthcare disparities.

    “The FST scale has been found to be unreliable for darker skin, not taking into account skin color ranges nor accurately providing skin cancer risk, ultimately leading to healthcare disparities.13,14”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [13] source

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    • cites [14] source

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  • May combine two claims.

    Premisecitation

    In vivo published data show high inter- and intrapublication variability, with differences among published absorption data being up to 9.6-fold and 2-fold for reported scattering data.

    “We have previously shown that in vivo published data show high inter- and intrapublication variability with differences among the published absorption data being up to 9.6- and 2-fold for reported scattering data.36”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [36] source

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  • May combine two claims.

    Premisecitation

    In neonates, skin location did not have a significant effect on optical coefficients, but absorption increased significantly in skin type V-VI compared with skin type I-II and III-IV patients with time after birth.

    “In neonates, skin location did not have a significant effect on optical coefficients, but absorption was shown to increase significantly in skin type V–VI compared with skin type I–II and III–IV patients with time after birth.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [42] source

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  • May combine two claims.

    Premisecitation

    Differences between skin types I-II and V-VI were significant for both absorption and scattering in the 600 to 850 nm and 600 to 750 nm ranges, respectively.

    “The differences between skin types I–II and V–VI were shown to be significant for both absorption and scattering in 600 to 850 nm and 600 to 750 nm ranges, respectively.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] source

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  • May combine two claims.

    Premisecitation

    For FST V-VI, absorption and scattering converged with the other skin types at 850 and 750 nm, respectively, indicating that the NIR is likely to be the region where FST may have less impact on optical properties.

    “For FST V–VI absorption and scattering converged with the other skin types at 850 and 750 nm, respectively, indicating that the NIR is likely to be the region where FST may have less impact on optical properties.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Absorption coefficients are at least an order of magnitude less than reduced scattering coefficients at these wavelengths, so absorption may have little effect on the distance light can travel through the skin or the amount of light that can reach the depths.

    “Absorption coefficients are, however, at least an order of magnitude less than reduced scattering coefficients at these wavelengths so absorption may have little effect on the distance light can travel through the skin or the amount of light that can reach the depths.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Because the TMFP is related to scattering, and the NIR is the region where scattering is least, this is the region where light is likely to travel the furthest distance into the skin.

    “Because the TMFP is related to scattering, and the NIR is the region where scattering is least (Sec. 3.2), this is the region where light is likely to travel the furthest distance into the skin.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    TMFP does not consider absorption, and a beam travelling through FST V-VI skin would likely be more affected by attenuation due to absorption than FST I-II.

    “It should be noted that TMFP does not consider absorption and a beam travelling through FST V–VI skin would likely be more affected by attenuation due to absorption than FST I–II.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    It seems unlikely that absorption by FST V-VI would be less than by lighter FSTs due to the expected absorption by melanin; therefore differences may be attributed to author methods, sample numbers and locations, and potentially to determination of FST being subjective.

    “It seems unlikely that absorption by FST V–VI would be less than by lighter FSTs due to the expected absorption by melanin and therefore differences may be attributed to author methods, sample numbers and locations, and potentially to determination of FST being subjective.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    In general, subjects with skin types I and II had the least absorption in the visible spectrum, while subjects with skin types IV, V, and VI had the greatest absorption in the visible spectrum, although there was some overlap with skin type III.

    “In general, subjects with skin types I and II had the least absorption in the visible spectrum. Subjects with skin types IV, V, and VI had the greatest absorption in the visible spectrum although there was some overlap with the data for skin type III.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [49] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The data contributing to the transmission calculations are extremely varied, and averaging of these is likely to have contributed to the similarity of the reduced scattering coefficients and therefore the percentage transmission.

    “The data contributing to the transmission calculations are extremely varied as shown in Fig 4; averaging of these is likely to have contributed to the similarity of the reduced scattering coefficients and therefore the percentage transmission”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

  • May combine two claims.

    Premisecitation

    FSTs II and III had the least absorption, with both spectra being similar, and FST IV absorption was between that of the palest and darkest skin.

    “FSTs II and III had the least absorption, with both spectra being similar and FST IV absorption was between that of the palest and darkest skin.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [39] source

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  • May combine two claims.

    Premisecitation

    Scattering for FST II was greatest and least for skin type VI up to 800 nm; beyond this all skin types had similar spectra.

    “Scattering for FST II was greatest and least for skin type VI up to 800 nm; beyond this all skin types had similar spectra.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [39] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The observed scattering differences in the visible spectrum are most likely due to absorption differences among skin types affecting scattered photon number and detection, i.e., FST V-VI absorbs more light in the visible region, so proportionally fewer photons are available to be scattered and detected than in FST I-II.

    “The observed scattering differences in the visible spectrum are most likely to be due to absorption differences among skin types in this spectrum affecting scattered photon number and detection, i.e., FST V–VI absorbs more light in the visible region, therefore, proportionally fewer photons are available to be scattered and detected than in FST I–II.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Interpretationreasoning

    For FST I-II and III-IV, more than 1% of light is most likely to be transmitted beyond 1.93 mm beyond 600 nm.

    “For FST I–II and III–IV, this is most likely to happen beyond 600 nm.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    OCT resolution and imaging depth are affected by absorption.

    “Because OCT resolution and imaging depth are affected by absorption, the melanin content of the skin and its effect on absorption need to be considered.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Longer wavelength light has the potential to follow a linear trajectory for a greater distance than shorter wavelength light, due to a reduction in scattering and absorption coefficients.

    “Sordillo et al.58 described the potential of longer wavelength light to follow a linear trajectory for a greater distance than shorter wavelength light, due to a reduction in scattering and absorption coefficients.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [58] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    OCT can be used to image to depths of up to 2 mm with resolution smaller than 10 μm.

    “OCT can be used to image to depths of up to 2 mm with resolution smaller than 10 μm.83,86”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [83] source

      Not checked in the free run.

    • cites [86] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    OCT, reflectance confocal microscopy, and multiphoton microscopy all use wavelengths beyond 700 nm and therefore avoid maximal melanin absorption, reducing the effect of skin color.

    “These all use wavelengths beyond 700 nm and therefore avoid maximal melanin absorption reducing the effect of skin color.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [82] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Light in the 1000 to 2000 nm spectrum can increase penetration depth into biological tissues, improve image resolution, reduce tissue autofluorescence, and aid image-based diagnostics.

    “For published data assembled by Shaw et al.,59 it was shown that light in the 1000 to 2000 nm spectrum can increase penetration depth into biological tissues, improve image resolution, reduce tissue autofluorescence, and aid image-based diagnostics.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [59] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Skin cancers are more prevalent in pale-skinned populations, with people with the darkest skin being diagnosed with approximately one twentieth of the cases of skin cancer of those with the palest skin.

    “This is probably because skin cancers are more prevalent in pale-skinned populations with the people with the darkest skin being diagnosed, with approximately one twentieth of the cases of skin cancer of those with the palest skin.126”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [126] Bradford, 2009, Skin cancer in skin of color

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    PPG monitors blood flow in real time.

    “photoplethysmography (PPG), which monitors blood flow in real time.130”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [130] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Water has multiple absorption peaks at infrared wavelengths.

    “whereas water has multiple absorption peaks at infrared wavelengths.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    ALA and MAL are absorbed into the skin becoming converted to protoporphyrin IX with a major absorption peak in the blue light spectrum (410 to 420 nm).

    “Both are absorbed into the skin becoming converted to protoporphyrin IX with a major absorption peak in the blue light spectrum (410 to 420 nm).61,110”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [61] source

      Not checked in the free run.

    • cites [110] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Morbidity in darker-skinned people is greater due to later diagnosis, with 70% 5-year survival rate in dark-skinned people compared with 92% in lighter-skinned people.

    “morbidity in darker-skinned people is greater due to later diagnosis, with 70% 5-year survival rate in dark-skinned people compared with 92% in lighter-skinned people.127”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [127] source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Hemoglobin in the blood and melanin in the skin are strong absorbers of visible light.

    “For example, hemoglobin in the blood and melanin in the skin are strong absorbers of visible light”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Absorption coefficients vary greatly depending upon the absorbing chromophores present.

    “however, absorption coefficients vary greatly depending upon the absorbing chromophores present.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    Selectivity of PDT is affected by uptake of the photosensitive drug by target cells, its metabolism to an active form, and penetration of the light source.

    “selectivity is affected by uptake of the photosensitive drug by target cells and its metabolism to an active form as well as by penetration of the light source.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    For PDT to be effective, a clear understanding of the propagation of light through human tissue is required, which is affected by local absorption and scattering coefficients.

    “For PDT to be effective, a clear understanding of the propagation of light through human tissue is required, which is affected by local absorption and scattering coefficients.3”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisenone given

    OCT tends to use wavelengths beyond 1300 nm for skin imaging.

    “although OCT tends to use wavelengths beyond 1300 nm for skin imaging”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    PDT requires that a photosensitive drug is activated in the presence of light and oxygen to produce reactive oxygen intermediates that irreversibly damage cells.

    “PDT requires that a photosensitive drug is activated in the presence of light and oxygen to produce reactive oxygen intermediates that irreversibly damage cells.61”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [61] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Chlorin has absorption at 662 nm and has been shown to be less painful to patients than MAL and ALA treatments.

    “A further photosensitizing drug, chlorin, comprising of chlorin e6, chlorin p6, and purpurin 5, has been approved for use in Russia and Republic of Korea with absorption at 662 nm and has been shown to be less painful to patients than MAL and ALA treatments.66,67,114”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [66] source

      Not checked in the free run.

    • cites [67] source

      Not checked in the free run.

    • cites [114] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The scattering coefficients of tissues decrease monotonically with increasing wavelength.

    “In general, the scattering coefficients of tissues decrease monotonically with increasing wavelength”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Inflammatory hyperpigmentation is a side effect more commonly associated with the treatment of patients with FST IV-V and is caused by excess synthesis and deposition of melanin enhanced by inflammatory responses.

    “Inflammatory hyperpigmentation is a side effect more commonly associated with the treatment of patients with FST IV–V and caused by excess synthesis and deposition of melanin enhanced by inflammatory responses.20”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [20] Sharma, 2022

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    MAL is more lipophilic than ALA, so it is absorbed more deeply into the skin and is commonly used in conjunction with red light, which penetrates more deeply into the skin than blue light.

    “Because MAL is more lipophilic than ALA it is absorbed more deeply into the skin and is therefore commonly used in conjunction with red light, which penetrates more deeply into the skin than blue light.112”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [112] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Blue light (450 to 495 nm) is used to maximize absorbance and longer wavelengths of light (beyond 620 nm) have best tissue penetration.

    “Blue light (450 to 495 nm) is used to maximize absorbance and longer wavelengths of light (beyond 620 nm) have best tissue penetration.107,108”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [107] source

      Not checked in the free run.

    • cites [108] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Potential reasons for the common association of inflammatory hyperpigmentation with dark skin are increased oxidative stress and reduced vasodilation, which are improved with vitamin D, as well as increased circulating inflammatory markers.

    “Potential reasons for the common association of inflammatory hyperpigmentation with dark skin are increased oxidative stress and reduced vasodilation, which are improved with vitamin D (the intrinsic production of which is reduced in darker skin), as well as increased circulating inflammatory markers, which could lead to impaired melanin production and altered skin cell activity.106”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [106] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Treatment with MAL-PDT has most commonly been associated with treatment of nonmelanoma skin cancers and, more recently, acne.

    “Treatment with MAL-PDT has most commonly been associated with treatment of nonmelanoma skin cancers and, more recently, acne.112,113”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [112] source

      Not checked in the free run.

    • cites [113] source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    An accurate measurement of skin color is essential for OCT imaging of skin cancers; for treatment of skin cancers and other skin conditions using PDT; and for medical monitoring using wearable devices.

    “An accurate measurement of skin color is essential for OCT imaging of, for example, skin cancers; for treatment of skin cancers and other skin conditions using PDT; and for medical monitoring using wearable devices.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    In theory, estimated oxygen saturation should be independent of FST and other variables.

    “In theory, because the measurements should only be dependent upon arterial saturation, the estimated oxygen saturation should be independent of FST and other variables.141”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [141] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    The skin is the first barrier to light for optical imaging.

    “The skin is the first barrier to light for optical imaging”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    Polarization is affected by scattering, which alters the degree of polarization.

    “Polarization is affected by scattering, which alters the degree of polarization”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisenone given

    A clear understanding of the optical properties of the tissues being measured is required to be able to interpret the results appropriately.

    “A clear understanding of the optical properties of the tissues being measured is required to be able to interpret the results appropriately.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Light of 680 or 810 nm is used due to its penetration depth and ability to differentiate between oxygenated and deoxygenated blood.

    “Light of 680 or 810 nm is used due to its penetration depth and ability to differentiate between oxygenated and deoxygenated blood.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Black and ethnic minority groups had poorest outcomes from COVID-19 infection and this was compounded by the overestimation of oxygen saturation.

    “Black and ethnic minority groups had poorest outcomes from COVID-19 infection and this was compounded by the overestimation of oxygen saturation.11,134”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [11] source

      Not checked in the free run.

    • cites [134] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The variation in optical properties with skin color is medically important, affecting optical medical technologies.

    “The variation in optical properties with skin color is medically important, affecting optical medical technologies.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Feiner et al. suggested that PO overestimates oxygen saturation in darker skin tones and up to 10% differences in saturation estimates were observed among different instruments.

    “However, issues were identified in 2007 by Feiner et al.,141 who suggested that PO overestimates oxygen saturation in darker skin tones and up to 10% differences in saturation estimates were observed among different instruments.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [141] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    For reflectance measurements used for heart rate monitoring, green light is usually used as this provides high quality PPG signals and is less affected by temperature changes and accuracy.

    “For reflectance measurements used, for example, for heart rate monitoring, green light is usually used as this provides high quality PPG signals and is less affected by temperature changes and accuracy.132”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [132] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    PO works in transmission and uses two light sources to measure oxygen saturation of the blood.

    “Currently, the most common form of PPG is PO, which works in transmission and uses two light sources to measure oxygen saturation of the blood.10”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [10] source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    There is huge potential for skin optical property inaccuracies due to melanin content.

    “Others agree that there is huge potential for skin optical property inaccuracies due to melanin content”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Other wearable healthcare products used to measure heart rate and arrhythmia have been shown to be limited by racial bias.

    “Other wearable healthcare products used to measure heart rate and arrhythmia, for example, have also been shown to be limited by racial bias.144”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [144] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Black patients were at much higher risk of having occult hypoxemia due to overestimation of blood saturation by PO, thereby limiting access to supplemental oxygen.

    “A recent study comparing arterial blood gas (invasive) with PO showed that Black patients were at much higher risk of having occult hypoxemia (an arterial oxygen blood saturation of <88%) due to overestimation of blood saturation by PO thereby limiting access to supplemental oxygen for Black patients.137”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [137] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Light intensity transmitted through the skin depends upon the volume of blood at the measurement site.

    “The light intensity transmitted through the skin will depend upon the volume of blood at the measurement site.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Imaging depth is dependent upon both the scattering and absorption properties of the skin, which depend on skin color and the wavelength of light.

    “imaging depth is dependent upon both its scattering and absorption properties, which depend on skin color and the wavelength of light.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Bent et al. investigated the reliability of wearable optical heart rate monitors on 53 subjects with a variety of FSTs and showed that these were unaffected by skin color.

    “On the contrary, Bent et al.145 investigated the reliability of wearable optical heart rate monitors on 53 subjects with a variety of FSTs and showed that that these were unaffected by skin color.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [145] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Conclusions about optical properties beyond 1000 nm are difficult to draw because published data are minimal and not equivalently representative of all FSTs.

    “Because the published data beyond 1000 nm are minimal and not equivalently representative of all FSTs conclusions are difficult to draw.”
    Quote in the paperSubstantial claim
88 of 88

  • The paper relies on this without support.

    The Fitzpatrick skin type scale does not quantify concentrations of melanin in the epidermis.

    “It is important to note that, although linked to the amount of melanin in the skin, the FST does not quantify concentrations of melanin in the epidermis.”

  • The paper relies on this without support.

    Averaging the collated published data across studies yields meaningful average absorption and reduced scattering coefficients for each FST group.

    “Here, we pool the data from the 12 papers measuring optical properties with respect to FST and average coefficients determined for three FST groupings: FST I–II, III–IV, and V–VI.”

  • The authors state this as an assumption.

    The expression Iout=Iin e−(μa+μs′)l is an ad hoc expression that will tend to overestimate the amount of light reaching a particular position.

    “We acknowledge that this is a somewhat ad hoc expression and will tend to overestimate the amount of light reaching a particular position, it will, however, give a useful ballpark and a method for considering the challenges of certain technologies with skin color.”

  • The authors state this as an assumption.

    The light available at a certain depth to form a focus has suffered far less scattering than a typical photon.

    “In this case, it is reasonable to say that the light available at a certain depth to form a focus has suffered far less scattering than a “typical” photon.”

  • The paper relies on this without support.

    FST is a valid proxy for skin color and melanin content.

    “Determination of FST is subjective; for the accuracy of future applications spectrometric determinations of skin type is required incorporating a direct measure of melanin content.”

  • The paper relies on this without support.

    The published data used to calculate average optical coefficients are representative of the respective FST groups.

    “Due to the variability and limited nature of the data that make up the averaged coefficients used for this work, it is difficult to reliably and precisely extract information.”

  • The paper relies on this without support.

    There are incorrect perceptions that skin cancers are unique to the lighter-skinned population.

    “Nevertheless, there are incorrect perceptions that skin cancers are unique to the lighter-skinned population”

  • The paper relies on this without support.

    Optical medical technologies currently have racial bias.

    “enabling removal of the racial bias currently associated with optical medical technologies”
    “consistent therapeutics without racial bias”
8 of 8

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Algorithm developmental biases stem from selecting features, adjusting training data composition, and model calibrations.

    “The accuracy of heart rate measurements affects people with darker skin tones because of algorithm developmental biases that stem from selecting features and adjusting training data composition and model calibrations [23-26].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [26]

    The “Medical Wearables and PO” section (page not provided) reports concerns about reduced accuracy of optical heart-rate devices for darker skin and notes that testing populations often lack diversity. It does not attribute the bias to feature selection, training-data composition, or model calibration; its discussion of testing populations is not evidence about training data. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • Long-term impacts of repeated underestimation in darker-skinned populations remain largely unexplored.

    “Long-term impacts of repeated underestimation in darker-skinned populations - such as chronic underdiagnosis of cardiovascular risk - remain largely unexplored, underscoring the need for standardized validation protocols and inclusion of diverse demographic groups in future studies [26].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [26]

    The Medical Wearables and PO section reports concerns that reduced device accuracy in darker skin may worsen healthcare disparities, and the Conclusions call for validation research that includes varied skin tones. But the paper does not establish that the long-term effects of repeated underestimation remain unexplored or discuss chronic underdiagnosis of cardiovascular risk. Its Introduction describes pulse oximeters as overestimating oxygen levels, rather than underestimating them. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conclusion reverses the reported absorption trend

    Major

    The conclusion says absorption is greater for FST I-II than FST V-VI across 400-1000 nm, whereas the results say the opposite over that range. Table 2 also shows greater absorption for FST V-VI at 620 nm (0.160 versus 0.041 mm−1).

  • Conclusion reverses the reported scattering trend

    Major

    The conclusion says reduced scattering is greater for FST I-II than FST V-VI from 600-1000 nm. The results instead say FST I-II coefficients are 22% to 48% less than those of the darker FSTs in that interval.

  • Reported absorption range does not hold at 410 nm

    Major

    The stated 400-1000 nm range includes 410 nm, but Table 2 gives a lower absorption coefficient for FST V-VI (0.675 mm−1) than for FST I-II (0.975 mm−1) at that wavelength.

3 of 3

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Related

Authors
Setchfield, K., Gorman, A., Simpson, A. H. R. W., Somekh, M. G., & Wright, A. J.
Affiliations
  • University of Nottingham (GB)
  • University of Edinburgh (GB)
  • The Univ. of Edinburgh
Corresponding author
Wright, Amanda J.
ORCID
Venue
Journal of Biomedical Optics
Publisher
SPIE-Intl Soc Optical Eng
Published
2024-01-24
Volume
29
Issue
01
Pages
1-25
ISSN
  • 1083-3668 (ISSN-L)
  • 1560-2281
DOI
10.1117/1.jbo.29.1.010901
PMC
PMC10807857
OpenAlex
W4391163776
Semantic Scholar
d603d050172aaa4542342f4c693a13de5f58a700
Cited by
72
References
137
Citations by year
2026: 27 · 2025: 32 · 2024: 13
FWCI
4.68
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Biomedical Optics (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Repository@Nottingham (University of Nottingham) (submittedVersion, cc-by)
  • Repository@Nottingham (University of Nottingham) (submittedVersion)
Funders
Engineering and Physical Sciences Research Council (EP/T020997, EP/T020997/2, EP/T020997/1)
Topics
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Optical Imaging and Spectroscopy Techniques
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biophysics › Spectroscopy Techniques in Biomedical and Chemical Research
Keywords
skin color, Fitzpatrick skin type, skin optical properties, optical absorption, light scattering, optical penetration depth, transport mean free path, pulse oximetry, skin pigmentation, photodynamic therapy, wearable medical devices, health care disparities
MeSH terms
COVID-19, Ethnicity, Humans, Minority Groups, Photochemotherapy, Skin Pigmentation

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

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