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Vasudevan S, Vogt WC, Weininger S, Pfefer TJ. Melanometry for objective evaluation of skin pigmentation in pulse oximetry studies. COMMUNICATIONS MEDICINE 2024; 4:138. [PMID: 38992188 PMCID: PMC11239860 DOI: 10.1038/s43856-024-00550-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 06/11/2024] [Indexed: 07/13/2024] Open
Abstract
Pulse oximetry enables real-time, noninvasive monitoring of arterial blood oxygen levels. However, results can vary with skin color, thus detecting disparities during clinical validation studies requires an accurate measure of skin pigmentation. Recent clinical studies have used subjective methods such as self-reported color, race/ethnicity to categorize skin. Melanometers based on optical reflectance may offer a more effective, objective approach to assess pigmentation. Here, we review melanometry approaches and assess evidence supporting their use as clinical research tools. We compare performance data, including repeatability, robustness to confounders, and compare devices to each other, to subjective methods, and high-quality references. Finally, we propose best practices for evaluating melanometers and discuss alternate optical approaches that may improve accuracy. Whilst evidence indicates that melanometers can provide superior performance to subjective approaches, we encourage additional research and standardization efforts, as these are needed to ensure consistent and reliable results in clinical studies.
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Affiliation(s)
- Sandhya Vasudevan
- Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA.
| | - William C Vogt
- Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
| | - Sandy Weininger
- Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
| | - T Joshua Pfefer
- Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
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Shugar AL, Konger RL, Rohan CA, Travers JB, Kim YL. Mapping cutaneous field carcinogenesis of nonmelanoma skin cancer using mesoscopic imaging of pro-inflammation cues. Exp Dermatol 2024; 33:e15076. [PMID: 38610095 PMCID: PMC11034840 DOI: 10.1111/exd.15076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 03/24/2024] [Accepted: 03/30/2024] [Indexed: 04/14/2024]
Abstract
Nonmelanoma skin cancers remain the most widely diagnosed types of cancers globally. Thus, for optimal patient management, it has become imperative that we focus our efforts on the detection and monitoring of cutaneous field carcinogenesis. The concept of field cancerization (or field carcinogenesis), introduced by Slaughter in 1953 in the context of oral cancer, suggests that invasive cancer may emerge from a molecularly and genetically altered field affecting a substantial area of underlying tissue including the skin. A carcinogenic field alteration, present in precancerous tissue over a relatively large area, is not easily detected by routine visualization. Conventional dermoscopy and microscopy imaging are often limited in assessing the entire carcinogenic landscape. Recent efforts have suggested the use of noninvasive mesoscopic (between microscopic and macroscopic) optical imaging methods that can detect chronic inflammatory features to identify pre-cancerous and cancerous angiogenic changes in tissue microenvironments. This concise review covers major types of mesoscopic optical imaging modalities capable of assessing pro-inflammatory cues by quantifying blood haemoglobin parameters and hemodynamics. Importantly, these imaging modalities demonstrate the ability to detect angiogenesis and inflammation associated with actinically damaged skin. Representative experimental preclinical and human clinical studies using these imaging methods provide biological and clinical relevance to cutaneous field carcinogenesis in altered tissue microenvironments in the apparently normal epidermis and dermis. Overall, mesoscopic optical imaging modalities assessing chronic inflammatory hyperemia can enhance the understanding of cutaneous field carcinogenesis, offer a window of intervention and monitoring for actinic keratoses and nonmelanoma skin cancers and maximise currently available treatment options.
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Affiliation(s)
- Andrea L. Shugar
- Department of Pharmacology & Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA
| | - Raymond L. Konger
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Pathology, Richard L. Roudebush Veterans Administration Hospital, Indianapolis, Indiana, USA
| | - Craig A. Rohan
- Department of Pharmacology & Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA
- Department of Dermatology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA
- Department of Medicine, Dayton Veterans Affairs Medical Center, Dayton, Ohio, USA
| | - Jeffrey B. Travers
- Department of Pharmacology & Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA
- Department of Dermatology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA
- Department of Medicine, Dayton Veterans Affairs Medical Center, Dayton, Ohio, USA
| | - Young L. Kim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- Purdue Institute for Cancer Research, Purdue University, West Lafayette, Indiana, USA
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Else TR, Hacker L, Gröhl J, Bunce EV, Tao R, Bohndiek SE. Effects of skin tone on photoacoustic imaging and oximetry. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:S11506. [PMID: 38125716 PMCID: PMC10732256 DOI: 10.1117/1.jbo.29.s1.s11506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 11/02/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023]
Abstract
Significance Photoacoustic imaging (PAI) provides contrast based on the concentration of optical absorbers in tissue, enabling the assessment of functional physiological parameters such as blood oxygen saturation (sO 2 ). Recent evidence suggests that variation in melanin levels in the epidermis leads to measurement biases in optical technologies, which could potentially limit the application of these biomarkers in diverse populations. Aim To examine the effects of skin melanin pigmentation on PAI and oximetry. Approach We evaluated the effects of skin tone in PAI using a computational skin model, two-layer melanin-containing tissue-mimicking phantoms, and mice of a consistent genetic background with varying pigmentations. The computational skin model was validated by simulating the diffuse reflectance spectrum using the adding-doubling method, allowing us to assign our simulation parameters to approximate Fitzpatrick skin types. Monte Carlo simulations and acoustic simulations were run to obtain idealized photoacoustic images of our skin model. Photoacoustic images of the phantoms and mice were acquired using a commercial instrument. Reconstructed images were processed with linear spectral unmixing to estimate blood oxygenation. Linear unmixing results were compared with a learned unmixing approach based on gradient-boosted regression. Results Our computational skin model was consistent with representative literature for in vivo skin reflectance measurements. We observed consistent spectral coloring effects across all model systems, with an overestimation of sO 2 and more image artifacts observed with increasing melanin concentration. The learned unmixing approach reduced the measurement bias, but predictions made at lower blood sO 2 still suffered from a skin tone-dependent effect. Conclusion PAI demonstrates measurement bias, including an overestimation of blood sO 2 , in higher Fitzpatrick skin types. Future research should aim to characterize this effect in humans to ensure equitable application of the technology.
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Affiliation(s)
- Thomas R. Else
- University of Cambridge, CRUK Cambridge Institute, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
| | - Lina Hacker
- University of Cambridge, CRUK Cambridge Institute, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
| | - Janek Gröhl
- University of Cambridge, CRUK Cambridge Institute, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
| | - Ellie V. Bunce
- University of Cambridge, CRUK Cambridge Institute, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
| | - Ran Tao
- University of Cambridge, CRUK Cambridge Institute, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
| | - Sarah E. Bohndiek
- University of Cambridge, CRUK Cambridge Institute, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
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Setchfield K, Gorman A, Simpson AHRW, Somekh MG, Wright AJ. Effect of skin color on optical properties and the implications for medical optical technologies: a review. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:010901. [PMID: 38269083 PMCID: PMC10807857 DOI: 10.1117/1.jbo.29.1.010901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 12/15/2023] [Accepted: 12/26/2023] [Indexed: 01/26/2024]
Abstract
Significance Skin 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. Aim The 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. Approach Published 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. Results Variation 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. Conclusions Current 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.
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Affiliation(s)
- Kerry Setchfield
- University of Nottingham, Faculty of Engineering, Optics and Photonics Research Group, Nottingham, United Kingdom
| | - Alistair Gorman
- University of Edinburgh, School of Engineering, Edinburgh, United Kingdom
| | - A. Hamish R. W. Simpson
- University of Edinburgh, Department of Orthopaedics, Division of Clinical and Surgical Sciences, Edinburgh, United Kingdom
| | - Michael G. Somekh
- University of Nottingham, Faculty of Engineering, Optics and Photonics Research Group, Nottingham, United Kingdom
- Zhejiang Lab, Hangzhou, China
| | - Amanda J. Wright
- University of Nottingham, Faculty of Engineering, Optics and Photonics Research Group, Nottingham, United Kingdom
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Jonasson H, Fredriksson I, Bergstrand S, Östgren CJ, Larsson M, Strömberg T. Absorption and reduced scattering coefficients in epidermis and dermis from a Swedish cohort study. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:115001. [PMID: 38078153 PMCID: PMC10704088 DOI: 10.1117/1.jbo.28.11.115001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 09/25/2023] [Accepted: 10/30/2023] [Indexed: 12/18/2023]
Abstract
Significance Knowledge of optical properties is important to accurately model light propagation in tissue, but in vivo reference data are sparse. Aim The aim of our study was to present in vivo skin optical properties from a large Swedish cohort including 3809 subjects using a three-layered skin model and spatially resolved diffuse reflectance spectroscopy (Periflux PF6000 EPOS). Approach Diffuse reflectance spectra (475 to 850 nm) at 0.4 and 1.2 mm source-detector separations were analyzed using an inverse Monte Carlo method. The model had one epidermis layer with variable thicknesses and melanin-related absorptions and two dermis layers with varying hemoglobin concentrations and equal oxygen saturations. The reduced scattering coefficient was equal across all layers. Results Median absorption coefficients (mm - 1 ) in the upper dermis ranged from 0.094 at 475 nm to 0.0048 at 850 nm and similarly in the lower dermis from 0.059 to 0.0035. The reduced scattering coefficient (mm - 1 ) ranged from 3.22 to 1.20, and the sampling depth (mm) ranged from 0.23 to 0.38 (0.4 mm separation) and from 0.49 to 0.68 (1.2 mm separation). There were differences in optical properties across sex, age groups, and BMI categories. Conclusions Reference material for skin optical properties is presented.
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Affiliation(s)
- Hanna Jonasson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Ingemar Fredriksson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
- Perimed AB, Järfälla, Stockholm, Sweden
| | - Sara Bergstrand
- Linköping University, Department of Health, Medicine, and Caring Sciences, Linköping, Sweden
| | - Carl Johan Östgren
- Linköping University, Department of Health, Medicine, and Caring Sciences, Linköping, Sweden
- Linköping University, Centre of Medical Image Science and Visualization Linköping, Sweden
| | - Marcus Larsson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Tomas Strömberg
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
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Wickramasinghe VA, Decker SM, Streeter SS, Sloop AM, Petusseau AF, Alexander DA, Bruza P, Gladstone DJ, Zhang R, Pogue BW. Color-resolved Cherenkov imaging allows for differential signal detection in blood and melanin content. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:036005. [PMID: 36923987 PMCID: PMC10008915 DOI: 10.1117/1.jbo.28.3.036005] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
Significance High-energy x-ray delivery from a linear accelerator results in the production of spectrally continuous broadband Cherenkov light inside tissue. In the absence of attenuation, there is a linear relationship between Cherenkov emission and deposited dose; however, scattering and absorption result in the distortion of this linear relationship. As Cherenkov emission exits the absorption by tissue dominates the observed Cherenkov emission spectrum. Spectroscopic interpretation of this effects may help to better relate Cherenkov emission to ionizing radiation dose delivered during radiotherapy. Aim In this study, we examined how color Cherenkov imaging intensity variations are caused by absorption from both melanin and hemoglobin level variations, so that future Cherenkov emission imaging might be corrected for linearity to delivered dose. Approach A custom, time-gated, three-channel intensified camera was used to image the red, green, and blue wavelengths of Cherenkov emission from tissue phantoms with synthetic melanin layers and varying blood concentrations. Our hypothesis was that spectroscopic separation of Cherenkov emission would allow for the identification of attenuated signals that varied in response to changes in blood content versus melanin content, because of their different characteristic absorption spectra. Results Cherenkov emission scaled with dose linearly in all channels. Absorption in the blue and green channels increased with increasing oxy-hemoglobin in the blood to a greater extent than in the red channel. Melanin was found to absorb with only slight differences between all channels. These spectral differences can be used to derive dose from measured Cherenkov emission. Conclusions Color Cherenkov emission imaging may be used to improve the optical measurement and determination of dose delivered in tissues. Calibration for these factors to minimize the influence of the tissue types and skin tones may be possible using color camera system information based upon the linearity of the observed signals.
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Affiliation(s)
| | - Savannah M. Decker
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Samuel S. Streeter
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Austin M. Sloop
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Arthur F. Petusseau
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Daniel A. Alexander
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Petr Bruza
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - David J. Gladstone
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
- Dartmouth College, Geisel School of Medicine, Department of Medicine, Hanover, New Hampshire, United States
| | - Rongxiao Zhang
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
- Dartmouth College, Geisel School of Medicine, Department of Medicine, Hanover, New Hampshire, United States
| | - Brian W. Pogue
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
- University of Wisconsin–Madison, Department of Medical Physics, Madison, Wisconsin, United States
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