Dr. Gordon T. Kennedy Profile

Dr. Gordon T. Kennedy

Project Scientist at Beckman Laser Institute and Medical Clinic

SPIE Involvement:

Author

Publications (41)

SPIE Journal Paper | 1 August 2024 Open Access

Open Access

Multimodal optical imaging of the oculofacial region using a solid tissue-simulating facial phantom

Lilangi S. Ediriwickrema, Shijun Sung, Kaylyn Mattick, Miranda An, Claire Malley, Stephanie Kirk, Divya Devineni, Jaylen Lee, Gordon Kennedy, Bernard Choi, Anthony Durkin

JBO, Vol. 29, Issue 08, 086002, (August 2024) https://doi.org/10.1117/12.10.1117/1.JBO.29.8.086002

KEYWORDS: Optical properties, Tissues, Optical imaging, Scattering, Light sources and illumination, Anatomy, Absorption, Optical testing, Biological imaging, Skin

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SignificanceSpatial frequency domain imaging (SFDI) applies patterned near-infrared illumination to quantify the optical properties of subsurface tissue. The periocular region is unique due to its complex ocular adnexal anatomy. Although SFDI has been successfully applied to relatively flat in vivo tissues, regions that have significant height variations and curvature may result in optical property inaccuracies.AimWe characterize the geometric impact of the periocular region on SFDI imaging reliability.ApproachSFDI was employed to measure the reduced scattering coefficient (μs′) and absorption coefficient (μa) of the periocular region in a cast facial tissue-simulating phantom by capturing images along regions of interest (ROIs): inferior temporal quadrant (ITQ), inferior nasal quadrant (INQ), superior temporal quadrant (STQ), central eyelid margin (CEM), rostral lateral nasal bridge (RLNB), and forehead (FH). The phantom was placed on a chin rest and imaged nine times from an “en face” or “side profile” position, and the flat back of the phantom was measured 15 times.ResultsThe measured μa and μs′ of a cast facial phantom are accurate when comparing the ITQ, INQ, STQ, and FH to its flat posterior surface. Paired t tests of ITQ, INQ, STQ, and FH μa and μs′ concluded that there is not enough evidence to suggest that imaging orientation impacted the measurement accuracy. Regions of extreme topographical variation, i.e., CEM and RLNB, did exhibit differences in measured optical properties.ConclusionsWe are the first to evaluate the geometric implications of wide-field imaging along the periocular region using a solid tissue-simulating facial phantom. Results suggest that the ITQ, INQ, STQ, and FH of a generalized face have minimal impact on the SFDI measurement accuracy. Areas with heightened topographic variation exhibit measurement variability. Device and facial positioning do not appear to bias measurements. These findings confirm the need to carefully select ROIs when measuring optical properties along the periocular region.

Proceedings Article | 13 March 2024 Poster

Poster

Early detection of cutaneous neurofibromas using spatial frequency domain imaging and optical coherence tomography

Junsoo Lee, Wangcun Jia, Gordon Kennedy, Nitesh Katta, Rafael Sierra, James Johnson, Kristen Kelly, Anthony Durkin, J. Stuart Nelson, Thomas Milner

Proceedings Volume PC12816, PC128160R (2024) https://doi.org/10.1117/12.3001848

KEYWORDS: Optical coherence tomography, Coherence imaging, Optical imaging, Skin, Scattering, Optical properties, Imaging systems, Eye, Tissue optics, Light sources and illumination

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Proceedings Article | 13 March 2024 Presentation

Presentation

Optical properties of in-vivo normal and burned skin in humans and swine measured using spatial frequency domain imaging (SFDI)

Gordon Kennedy, Rebecca Rowland, Thinh Phan, Chris Campbell, Alexis Fox, Earl Steward, Bernard Choi, Theresa Chin, Victor Joe, Anthony Durkin, Robert Christy, David Burmeister

Proceedings Volume PC12833, PC128330E (2024) https://doi.org/10.1117/12.3003470

KEYWORDS: Skin, Optical properties, In vivo imaging, Systems modeling, Tissues, Wound healing, Toxicology, Tissue optics, Pathophysiology, Oxygen

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Proceedings Article | 13 March 2024 Presentation + Paper

Presentation + Paper

Accurate burn wound categorization using an optimized spatial frequency domain imaging device and machine learning

Chris Campbell, Gordon Kennedy, Rebecca Rowland, Alexis Fox, Earl Steward, Theresa Chin, Victor Joe, Anthony Durkin

Proceedings Volume 12816, 1281604 (2024) https://doi.org/10.1117/12.3002918

KEYWORDS: Skin, Machine learning, Tissues, Spatial frequencies, Imaging devices

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Proceedings Article | 13 March 2024 Presentation + Paper

Presentation + Paper

Simultaneous imaging of shallow and deep tissues based on multi-line scanning

Naoshi Yoneyama, Sota Nakazawa, Kanta Iyanagi, Yusuke Tanihata, Ryotaro Mori, Manabu Machida, Gordon Kennedy, Anthony Durkin, Keiichiro Kagawa

Proceedings Volume 12816, 1281608 (2024) https://doi.org/10.1117/12.3000865

KEYWORDS: Tissues, Near infrared spectroscopy, Tissue optics, Absorption, Monte Carlo methods, Silicon, Reflectivity, Diffuse reflectance spectroscopy, Scattering, Optical testing

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SPIE Journal Paper | 15 February 2024 Open Access

Open Access

Review of machine learning for optical imaging of burn wound severity assessment

Robert H. Wilson, Rebecca Rowland, Gordon T. Kennedy, Chris Campbell, Victor C. Joe, Theresa L. Chin, David M. Burmeister, Robert J. Christy, Anthony J. Durkin

JBO, Vol. 29, Issue 02, 020901, (February 2024) https://doi.org/10.1117/12.10.1117/1.JBO.29.2.020901

KEYWORDS: Education and training, Tissues, Image classification, Optical imaging, Deep learning, Machine learning, Skin, Optical coherence tomography, Image segmentation, Multispectral imaging

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SPIE Journal Paper | 18 January 2024 Open Access

Open Access

Motion-resistant three-wavelength spatial frequency domain imaging system with ambient light suppression using an 8-tap CMOS image sensor

Yu Feng, Chen Cao, Yuto Shimada, Keita Yasutomi, Shoji Kawahito, Gordon Kennedy, Anthony Durkin, Keiichiro Kagawa

JBO, Vol. 29, Issue 01, 016006, (January 2024) https://doi.org/10.1117/12.10.1117/1.JBO.29.1.016006

KEYWORDS: Image sensors, Imaging systems, Reflectivity, Tissues, Video, Biomedical optics, Image processing, Skin, In vivo imaging, Optical properties

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SignificanceWe present a motion-resistant three-wavelength spatial frequency domain imaging (SFDI) system with ambient light suppression using an 8-tap complementary metal-oxide semiconductor (CMOS) image sensor (CIS) developed at Shizuoka University. The system addresses limitations in conventional SFDI systems, enabling reliable measurements in challenging imaging scenarios that are closer to real-world conditions.AimOur study demonstrates a three-wavelength SFDI system based on an 8-tap CIS. We demonstrate and evaluate the system’s capability of mitigating motion artifacts and ambient light bias through tissue phantom reflectance experiments and in vivo volar forearm experiments.ApproachWe incorporated the Hilbert transform to reduce the required number of projected patterns per wavelength from three to two per spatial frequency. The 8-tap image sensor has eight charge storage diodes per pixel; therefore, simultaneous image acquisition of eight images based on multi-exposure is possible. Taking advantage of this feature, the sensor simultaneously acquires images for planar illumination, sinusoidal pattern projection at three wavelengths, and ambient light. The ambient light bias is eliminated by subtracting the ambient light image from the others. Motion artifacts are suppressed by reducing the exposure and projection time for each pattern while maintaining sufficient signal levels by repeating the exposure. The system is compared to a conventional SFDI system in tissue phantom experiments and then in vivo measurements of human volar forearms.ResultsThe 8-tap image sensor-based SFDI system achieved an acquisition rate of 9.4 frame sets per second, with three repeated exposures during each accumulation period. The diffuse reflectance maps of three different tissue phantoms using the conventional SFDI system and the 8-tap image sensor-based SFDI system showed good agreement except for high scattering phantoms. For the in vivo volar forearm measurements, our system successfully measured total hemoglobin concentration, tissue oxygen saturation, and reduced scattering coefficient maps of the subject during motion (16.5 cm/s) and under ambient light (28.9 lx), exhibiting fewer motion artifacts compared with the conventional SFDI.ConclusionsWe demonstrated the potential for motion-resistant three-wavelength SFDI system with ambient light suppression using an 8-tap CIS.

SPIE Journal Paper | 3 October 2023 Open Access

Open Access

Quantitative hemodynamic imaging: a method to correct the effects of optical properties on laser speckle imaging

Thinh Phan, Christian Crouzet, Gordon T. Kennedy, Anthony J. Durkin, Bernard Choi

NPh, Vol. 10, Issue 04, 045001, (October 2023) https://doi.org/10.1117/12.10.1117/1.NPh.10.4.045001

KEYWORDS: Optical properties, Hemodynamics, Digital micromirror devices, Speckle, Imaging systems, Neurophotonics, Cameras, Animals, Silicon, Light sources and illumination

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SignificanceStudying cerebral hemodynamics may provide diagnostic information on neurological conditions. Wide-field imaging techniques, such as laser speckle imaging (LSI) and optical intrinsic signal imaging, are commonly used to study cerebral hemodynamics. However, they often do not account appropriately for the optical properties of the brain that can vary among subjects and even during a single measurement. Here, we describe the combination of LSI and spatial-frequency domain imaging (SFDI) into a wide-field quantitative hemodynamic imaging (QHI) system that can correct the effects of optical properties on LSI measurements to achieve a quantitative measurement of cerebral blood flow (CBF).AimWe describe the design, fabrication, and testing of QHI.ApproachThe QHI hardware combines LSI and SFDI with spatial and temporal synchronization. We characterized system sensitivity, accuracy, and precision with tissue-mimicking phantoms. With SFDI optical property measurements, we describe a method derived from dynamic light scattering to obtain absolute CBF values from LSI and SFDI measurements. We illustrate the potential benefits of absolute CBF measurements in resting-state and dynamic experiments.ResultsQHI achieved a 50-Hz raw acquisition frame rate with a 10 × 10 mm field of view and flow sensitivity up to ∼4 mm / s. The extracted SFDI optical properties agreed well with a commercial system (R2 ≥ 0.98). The system showed high stability with low coefficients of variations over multiple sessions within the same day (<1 % ) and over multiple days (<4 % ). When optical properties were considered, the in-vivo hypercapnia gas challenge showed a slight difference in CBF (−1.5 % to 0.5% difference). The in-vivo resting-state experiment showed a change in CBF ranking for nine out of 13 animals when the correction method was applied to LSI CBF measurements.ConclusionsWe developed a wide-field QHI system to account for the confounding effects of optical properties on CBF LSI measurements using the information obtained from SFDI.

Proceedings Article | 17 March 2023 Presentation

Presentation

Absolute measurement of blood flow using a wide-field cerebral metabolic imaging (CMI) system

Thinh Phan, Christian Crouzet, Gordon Kennedy, Anthony Durkin, Bernard Choi

Proceedings Volume PC12365, PC1236502 (2023) https://doi.org/10.1117/12.2648084

KEYWORDS: Imaging systems, Blood circulation, Speckle, Dubnium, Optical testing, Optical properties, Diffusion, Scattering, Pixel resolution, Oxygen

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Proceedings Article | 17 March 2023 Presentation

Presentation

Comparative evaluation of conventional color imaging and hyperspectral imaging data as inputs to machine learning algorithms for classifying burn severity

Samagra Pandey, Gordon Kennedy, Rebecca Rowland, Victor Joe, Theresa Chin, Robert Christy, David Burmeister, Robert Wilson, Anthony Durkin

Proceedings Volume PC12352, PC1235207 (2023) https://doi.org/10.1117/12.2664961

KEYWORDS: Machine learning, Color imaging, Hyperspectral imaging, Data modeling, Multispectral imaging, Digital color imaging, Diffuse optical imaging, Biopsy

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Proceedings Article | 7 March 2023 Presentation + Paper

Presentation + Paper

Demonstration of motion-resistant three-wavelength spatial frequency domain imaging system with ambient light suppression using an 8-tap CMOS image sensor

Yu Feng, Yuto Shimada, Chen Cao, Keita Yasutomi, Shoji Kawahito, Gordon Kennedy, Anthony Durkin, Keiichiro Kagawa

Proceedings Volume 12376, 123760D (2023) https://doi.org/10.1117/12.2649418

KEYWORDS: Image sensors, CMOS sensors, Tissues, Reflectivity, Imaging systems, Light scattering, Scattering, Cameras, Biological imaging, Sensors

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Proceedings Article | 6 March 2023 Presentation

Presentation

Characterizing and overcoming the confounding effects of skin pigmentation for improved quantification of tissue oxygenation and hemodynamic changes across all skin types

Robert Wilson, Gordon Kennedy, Thinh Phan, Wei Jin, Anthony Durkin

Proceedings Volume PC12375, PC1237506 (2023) https://doi.org/10.1117/12.2650525

KEYWORDS: Skin, Tissues, Hemodynamics, Tissue optics, Oxygen, Spatial frequencies, Oximeters, Natural surfaces, Monte Carlo methods, Mathematical modeling

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SPIE Journal Paper | 23 March 2022 Open Access

Open Access

Quantifying the confounding effect of pigmentation on measured skin tissue optical properties: a comparison of colorimetry with spatial frequency domain imaging

Thinh Phan, Rebecca Rowland, Adrien Ponticorvo, Binh Le, Seyed Sharif, Gordon Kennedy, Robert Wilson, Anthony Durkin

JBO, Vol. 27, Issue 03, 036002, (March 2022) https://doi.org/10.1117/12.10.1117/1.JBO.27.3.036002

KEYWORDS: Skin, Tissue optics, Optical properties, Scattering, Absorption, Optical testing, Colorimetry, Tissues, Data modeling, Monte Carlo methods

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Significance: Spatial frequency domain imaging (SFDI) is a wide-field diffuse optical imaging technique for separately quantifying tissue reduced scattering (μs ′ ) and absorption (μa) coefficients at multiple wavelengths, providing wide potential utility for clinical applications such as burn wound characterization and cancer detection. However, measured μs ′ and μa can be confounded by absorption from melanin in patients with highly pigmented skin. This issue arises because epidermal melanin is highly absorbing for visible wavelengths and standard homogeneous light–tissue interaction models do not properly account for this complexity. Tristimulus colorimetry (which quantifies pigmentation using the L * “lightness” parameter) can provide a point of comparison between μa, μs ′ , and skin pigmentation. Aim: We systematically compare SFDI and colorimetry parameters to quantify confounding effects of pigmentation on measured skin μs ′ and μa. We assess the correlation between SFDI and colorimetry parameters as a function of wavelength. Approach: μs ′ and μa from the palm and ventral forearm were measured for 15 healthy subjects with a wide range of skin pigmentation levels (Fitzpatrick types I to VI) using a Reflect RS® (Modulim, Inc., Irvine, California) SFDI instrument (eight wavelengths, 471 to 851 nm). L * was measured using a Chroma Meter CR-400 (Konica Minolta Sensing, Inc., Tokyo). Linear correlation coefficients were calculated between L * and μs ′ and between L * and μa at all wavelengths. Results: For the ventral forearm, strong linear correlations between measured L * and μs ′ values were observed at shorter wavelengths (R > 0.92 at ≤659 nm), where absorption from melanin confounded the measured μs ′ . These correlations were weaker for the palm (R < 0.59 at ≤659 nm), which has less melanin than the forearm. Similar relationships were observed between L * and μa. Conclusions: We quantified the effects of epidermal melanin on skin μs ′ and μa measured with SFDI. This information may help characterize and correct pigmentation-related inaccuracies in SFDI skin measurements.

Proceedings Article | 7 March 2022 Presentation

Presentation

Widefield imaging of deep and superficial hemodynamics during an arterial vascular occlusion of the volar forearm

Gordon Kennedy, Rebecca Rowland, Amaan Mazhar, David Cuccia, Anthony Durkin

Proceedings Volume PC11934, PC1193401 (2022) https://doi.org/10.1117/12.2610540

KEYWORDS: Oxygen, Ischemia, Image analysis, Data acquisition, Hemodynamics, Tissues, Near infrared spectroscopy

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Proceedings Article | 2 March 2022 Presentation + Paper

Presentation + Paper

Demonstration of 3-band spatial frequency domain imaging using an 8-tap CMOS image sensor resistant to subject motion and ambient light

Kazuki Takada, Yuto Shimada, Keita Yasutomi, Shoji Kawahito, Gordon Kennedy, Anthony Durkin, Keiichiro Kagawa

Proceedings Volume 11951, 1195106 (2022) https://doi.org/10.1117/12.2608412

KEYWORDS: CMOS sensors, Scattering, Sensors, Absorption, Tissues, Reflectivity, Oxygen, Image sensors, Imaging systems, Spatial frequencies

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Proceedings Article | 2 March 2022 Presentation + Paper

Presentation + Paper

A 2x2-aperture 4-tap multi-modal tissue imager for multi-band SFDI and MELSCI

Yuto Shimada, Kazuki Takada, Hoang Son Nam, Kakeru Miyazaki, Keita Yasutomi, Shoji Kawahito, Christian Crouzet, Bernard Choi, Gordon Kennedy, Anthony Durkin, Keiichiro Kagawa

Proceedings Volume 11951, 1195107 (2022) https://doi.org/10.1117/12.2608397

KEYWORDS: Tissues, Imaging systems, CMOS sensors, Image sensors, Scattering, Tissue optics

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SPIE Journal Paper | 12 August 2021 Open Access

Open Access

Spatial frequency domain imager based on a compact multiaperture camera: testing and feasibility for noninvasive burn severity assessment

Gordon Kennedy, Keiichiro Kagawa, Rebecca Rowland, Adrien Ponticorvo, Jun Tanida, Anthony J Durkin

JBO, Vol. 26, Issue 08, 086001, (August 2021) https://doi.org/10.1117/12.10.1117/1.JBO.26.8.086001

KEYWORDS: Imaging systems, Cameras, Optical properties, Tissue optics, Scattering, Skin, Tissues, Optical testing, Remote sensing, Injuries

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Significance: Spatial frequency domain imaging (SFDI) is a wide-field imaging technique that provides quantitative maps of tissue optical properties. We describe a compact SFDI imager that employs a multispectral compound-eye camera. This design enables simultaneous image acquisition at multiple wavelengths. Such a device has potential for application for quantitative evaluation of superficial tissues by nonspecialists in low-resource settings. Aim: The aim of this work was to develop a compact SFDI imager for widefield imaging of in-vivo tissue optical properties and verify its ability to measure optical properties of tissue-simulating phantoms and in a preclinical model of burn wounds. Approach: This compound-eye imager was constructed using a CMOS sensor subdivided into multiple regions, each having a bandpass filter and objective lens. The ability of the instrument to image optical properties was compared with (1) a commercial SFDI imager and (2) a laboratory-based system. Initial validation of ability to accurately characterize optical properties was performed using a tissue-simulating optical phantom. It was then applied to an established murine model of thermal contact burn severity. In-vivo measurements of the optical properties of rat skin were performed before and after the application of burns. Histology was used to verify burn severity. Results: Measurements of the tissue-simulating phantom optical properties made using the compound-eye imager agree with measurements made using the two comparison SFDI devices. For the murine burn model, the burns showed a decrease in the reduced scattering coefficient at all measurement wavelengths compared with preburn measurements at the same locations. This is consistent with previously reported changes in scattering that occur in full-thickness burns. Conclusion: We demonstrate the potential for SFDI to be translated into compact form factor using a compound-eye camera that is capable of obtaining multiple wavelengths channels simultaneously.

Proceedings Article | 30 March 2021 Presentation

Presentation

A multi-aperture multi-tap image sensor for simultaneous multi-band SFDI and multi-exposure laser speckle contrast blood flow imaging

Keiichiro Kagawa, Gordon Kennedy, Adrien Ponticorvo, Iori Shibata, Keita Yasutomi, Shoji Kawahito, Jun Tanida, Christian Crouzet, Bernard Choi, Anthony Durkin

Proceedings Volume 11651, 116510H (2021) https://doi.org/10.1117/12.2578055

KEYWORDS: Image sensors, Blood circulation, Speckle, Modulators, Laser speckle contrast imaging, Imaging devices, Cameras, Video, Tissue optics, Spatial frequencies

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Proceedings Article | 5 March 2021 Poster + Presentation + Paper

Poster + Presentation + Paper

Monitoring superficial water content for systemic burn resuscitation with spatial frequency domain imaging

Rebecca Rowland, Gordon Kennedy, Adrien Ponticorvo, Jamila Duarte, David Burmeister, Robert Christy, Anthony Durkin

Proceedings Volume 11618, 116181A (2021) https://doi.org/10.1117/12.2576798

KEYWORDS: Imaging systems, Water, Tissues, Scattering, Absorption, Spatial frequencies, Skin, Scatter measurement, Reflectivity

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Proceedings Article | 5 March 2021 Presentation

Presentation

A clinical feasibility study of burn assessment using spatial frequency domain imaging and laser speckle imaging

Adrien Ponticorvo, Rebecca Rowland, Gordon Kennedy, David Burmeister, Robert Christy, Nicole Bernal, Anthony Durkin

Proceedings Volume 11618, 116180G (2021) https://doi.org/10.1117/12.2578999

KEYWORDS: Laser speckle imaging, Injuries, Speckle imaging, Visualization, Animal model studies, Standards development, Scattering, Scatter measurement, Ranging, New and emerging technologies

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Proceedings Article | 5 March 2021 Presentation + Paper

Presentation + Paper

A compact spatial frequency domain burn imager employing a compound–eye camera

Gordon Kennedy, Keiichiro Kagawa, Adrien Ponticorvo, Rebecca Rowland, Jun Tanida, Anthony Durkin

Proceedings Volume 11618, 116180H (2021) https://doi.org/10.1117/12.2579125

KEYWORDS: Imaging systems, Cameras, Scattering, Tunable filters, Tissues, Tissue optics, Spatial frequencies, Sensors, Optical properties

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Proceedings Article | 5 March 2021 Presentation + Paper

Presentation + Paper

An iterative method to quantify epidermal melanin concentration using spatial frequency domain Imaging and a layered Monte Carlo model

Wei Jin, Rebecca Rowland, Robert Wilson, Thinh Phan, Binh Cong Le, Gordon Kennedy, Anthony Durkin

Proceedings Volume 11618, 1161811 (2021) https://doi.org/10.1117/12.2579019

KEYWORDS: Skin, Monte Carlo methods, Iterative methods, Tissue optics, Reflectivity, Optical properties, Diffuse reflectance spectroscopy, Diffuse optical imaging, Absorption, Yield improvement

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Proceedings Article | 5 March 2021 Presentation

Presentation

Quantifying the confounding effect of pigmentation on measured skin tissue optical properties: A comparison of colorimetry with Spatial Frequency Domain Imaging

Thinh Phan, Rebecca Rowland, Adrien Ponticorvo, Binh Le, Robert Wilson, Seyed Sharif, Gordon Kennedy, Anthony Durkin

Proceedings Volume 11618, 1161810 (2021) https://doi.org/10.1117/12.2576800

KEYWORDS: Skin, Optical properties, In vivo imaging, Tissue optics, Scattering, Remote sensing, Range imaging, Monte Carlo methods, Mie scattering, Light wave propagation

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SPIE Journal Paper | 10 February 2021 Open Access

Open Access

Characterizing reduced scattering coefficient of normal human skin across different anatomic locations and Fitzpatrick skin types using spatial frequency domain imaging

Thinh Phan, Rebecca Rowland, Adrien Ponticorvo, Binh Le, Robert Wilson, Seyed Sharif, Gordon Kennedy, Nicole Bernal, Anthony Durkin

JBO, Vol. 26, Issue 02, 026001, (February 2021) https://doi.org/10.1117/12.10.1117/1.JBO.26.2.026001

KEYWORDS: Skin, Scattering, Optical properties, Absorption, In vivo imaging, Tissue optics, Wound healing, Tissues, Human subjects, Visible radiation

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Significance: Spatial frequency domain imaging (SFDI), a noncontact wide-field imaging technique using patterned illumination with multiple wavelengths, has been used to quantitatively measure structural and functional parameters of in vivo tissue. Using SFDI in a porcine model, we previously found that scattering changes in skin could potentially be used to noninvasively assess burn severity and monitor wound healing. Translating these findings to human subjects necessitates a better understanding of the variation in “baseline” human skin scattering properties across skin types and anatomical locations. Aim: Using SFDI, we aim to characterize the variation in the reduced scattering coefficient (μs′) for skin across a range of pigmentation and anatomic sites (including common burn locations) for normal human subjects. These measurements are expected to characterize baseline human skin properties to inform our use of SFDI for clinical burn severity and wound healing assessments. Approach: SFDI was used to measure μs′ in the visible- and near-infrared regime (471 to 851 nm) in 15 subjects at 10 anatomical locations. Subjects varied in age, gender, and Fitzpatrick skin type. Results: For all anatomical locations, the coefficient of variation in measured μs′ decreased with increasing wavelength. High intersubject variation in μs′ at visible wavelengths coincided with large values of the melanin extinction coefficient at those wavelengths. At 851 nm, where intersubject variation in μs′ was smallest for all anatomical locations and absorption from melanin is minimal, significant intrasubject differences in μs′ were observed at the different anatomical locations. Conclusions: Our study is the first report of wide-field mapping of human skin scattering properties across multiple skin types and anatomical locations using SFDI. Measured μs′ values varied notably between skin types at wavelengths where absorption from melanin was prominent. Additionally, μs′ varied considerably across different anatomical locations at 851 nm, where the confounding effects from melanin absorption are minimized.

SPIE Journal Paper | 16 July 2019 Open Access

Open Access

Spatial frequency domain imaging: a quantitative, noninvasive tool for in vivo monitoring of burn wound and skin graft healing

Gordon Kennedy, Randolph Stone, Andrew Kowalczewski, Rebecca Rowland, Jeffrey Chen, Melissa Baldado, Adrien Ponticorvo, Nicole Bernal, Robert Christy, Anthony Durkin

JBO, Vol. 24, Issue 07, 071615, (July 2019) https://doi.org/10.1117/12.10.1117/1.JBO.24.7.071615

KEYWORDS: Scattering, Skin, Wound healing, Tissues, Biopsy, Tissue optics, Optical properties, Collagen, In vivo imaging, Absorption

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SPIE Journal Paper | 3 July 2019 Open Access

Open Access

Hyperspectral imaging in the spatial frequency domain with a supercontinuum source

Mohammad Torabzadeh, Patrick Stockton, Gordon Kennedy, Rolf Saager, Anthony J. Durkin, Randy Bartels, Bruce Tromberg

JBO, Vol. 24, Issue 07, 071614, (July 2019) https://doi.org/10.1117/12.10.1117/1.JBO.24.7.071614

KEYWORDS: Absorption, Scattering, Tissue optics, Tissues, Hyperspectral imaging, Optical properties, Supercontinuum sources, Cameras, Digital micromirror devices, Chromophores

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SPIE Journal Paper | 27 May 2019 Open Access

Open Access

Burn wound classification model using spatial frequency-domain imaging and machine learning

Rebecca Rowland, Adrien Ponticorvo, Melissa Baldado, Gordon Kennedy, David Burmeister, Robert J. Christy, Nicole Bernal, Anthony Durkin

JBO, Vol. 24, Issue 05, 056007, (May 2019) https://doi.org/10.1117/12.10.1117/1.JBO.24.5.056007

KEYWORDS: Data modeling, Spatial frequencies, Machine learning, Reflectivity, Calibration, Skin, Multispectral imaging, Tissue optics, Tissues, Scattering

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Accurate assessment of burn severity is critical for wound care and the course of treatment. Delays in classification translate to delays in burn management, increasing the risk of scarring and infection. To this end, numerous imaging techniques have been used to examine tissue properties to infer burn severity. Spatial frequency-domain imaging (SFDI) has also been used to characterize burns based on the relationships between histologic observations and changes in tissue properties. Recently, machine learning has been used to classify burns by combining optical features from multispectral or hyperspectral imaging. Rather than employ models of light propagation to deduce tissue optical properties, we investigated the feasibility of using SFDI reflectance data at multiple spatial frequencies, with a support vector machine (SVM) classifier, to predict severity in a porcine model of graded burns. Calibrated reflectance images were collected using SFDI at eight wavelengths (471 to 851 nm) and five spatial frequencies (0 to 0.2 mm − 1). Three models were built from subsets of this initial dataset. The first subset included data taken at all wavelengths with the planar (0 mm − 1) spatial frequency, the second comprised data at all wavelengths and spatial frequencies, and the third used all collected data at values relative to unburned tissue. These data subsets were used to train and test cubic SVM models, and compared against burn status 28 days after injury. Model accuracy was established through leave-one-out cross-validation testing. The model based on images obtained at all wavelengths and spatial frequencies predicted burn severity at 24 h with 92.5% accuracy. The model composed of all values relative to unburned skin was 94.4% accurate. By comparison, the model that employed only planar illumination was 88.8% accurate. This investigation suggests that the combination of SFDI with machine learning has potential for accurately predicting burn severity.

Proceedings Article | 26 February 2019 Presentation + Paper

Presentation + Paper

A simple burn wound severity assessment classifier based on spatial frequency domain imaging (SFDI) and machine learning

Rebecca Rowland, Adrien Ponticorvo, Melissa Baldado, Gordon Kennedy, David Burmeister, Robert Christy, Nicole Bernal, Anthony Durkin

Proceedings Volume 10851, 1085109 (2019) https://doi.org/10.1117/12.2510670

KEYWORDS: Reflectivity, Machine learning, Calibration, Biopsy, Data modeling, Spatial frequencies, Skin, Tissues, Tissue optics, Scattering

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Proceedings Article | 26 February 2019 Presentation + Paper

Presentation + Paper

Characterization of debrided burn wounds using spatial frequency domain imaging

Gordon Kennedy, Randolph Stone, Andrew Kowalczewski, Jeffrey Chen, Rebecca Rowland, Adrien Ponticorvo, Robert Christy, Anthony Durkin

Proceedings Volume 10851, 108510O (2019) https://doi.org/10.1117/12.2510873

KEYWORDS: Scattering, Skin, Tissues, Scatter measurement, Wound healing, Medical research, Optical properties, Surgery, Injuries

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SPIE Journal Paper | 5 February 2019 Open Access

Open Access

Impact of hemoglobin breakdown products in the spectral analysis of burn wounds using spatial frequency domain spectroscopy

Rolf Saager, Rebecca Rowland, Melissa Baldado, Gordon Kennedy, Nicole Bernal, Adrien Ponticorvo, Robert Christy, Anthony Durkin

JBO, Vol. 24, Issue 02, 020501, (February 2019) https://doi.org/10.1117/12.10.1117/1.JBO.24.2.020501

KEYWORDS: Absorption, Tissues, Tissue optics, Wound healing, Spectroscopy, Data modeling, Spectral resolution, Injuries, Imaging spectroscopy, Imaging systems

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Proceedings Article | 14 March 2018 Presentation

Presentation

Spatial frequency domain imaging tracks healing following split-thickness skin grafts of burn wounds (Conference Presentation)

Gordon Kennedy, Randolph Stone, Andrew Kowalczewski, Jeffrey Chen, Rebecca Rowland, Melissa Baldado, Adrien Ponticorvo, Anthony Durkin

Proceedings Volume 10467, 104670E (2018) https://doi.org/10.1117/12.2290961

KEYWORDS: Wound healing, Scattering, Tissues, Skin, Diffuse optical imaging, In vivo imaging, Tissue optics, Optical properties, Absorption, Oxygen

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Proceedings Article | 22 February 2018 Presentation + Paper

Presentation + Paper

Spatial frequency domain imaging using a snap-shot filter mosaic camera with multi-wavelength sensitive pixels

Tomas Strömberg, Rolf Saager, Gordon Kennedy, Ingemar Fredriksson, Göran Salerud, Anthony Durkin, Marcus Larsson

Proceedings Volume 10467, 104670D (2018) https://doi.org/10.1117/12.2289357

KEYWORDS: Cameras, Multispectral imaging, RGB color model, Optical filters, Digital Light Processing, Absorption, Skin, Tissues, LED lighting, Light emitting diodes

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Spatial frequency domain imaging (SFDI) utilizes a digital light processing (DLP) projector for illuminating turbid media with sinusoidal patterns. The tissue absorption (μ_a) and reduced scattering coefficient (μ^,_s) are calculated by analyzing the modulation transfer function for at least two spatial frequencies. We evaluated different illumination strategies with a red, green and blue light emitting diodes (LED) in the DLP, while imaging with a filter mosaic camera, XiSpec, with 16 different multi-wavelength sensitive pixels in the 470-630 nm wavelength range. Data were compared to SFDI by a multispectral camera setup (MSI) consisting of four cameras with bandpass filters centered at 475, 560, 580 and 650 nm. A pointwise system for comprehensive microcirculation analysis was used (EPOS) for comparison. A 5-min arterial occlusion and release protocol on the forearm of a Caucasian male with fair skin was analyzed by fitting the absorption spectra of the chromophores HbO₂, Hb and melanin to the estimatedμ_a. The tissue fractions of red blood cells (fRBC), melanin (/mel) and the Hb oxygenation (^S0₂ ) were calculated at baseline, end of occlusion, early after release and late after release. EPOS results showed a decrease in ^S0₂ during the occlusion and hyperemia during release (^S0₂ = 40%, 5%, 80% and 51%). The fRBC showed an increase during occlusion and release phases. The best MSI resemblance to the EPOS was for green LED illumination (^S0₂ = 53%, 9%, 82%, 65%). Several illumination and analysis strategies using the XiSpec gave un-physiological results (e.g. negative ^S0₂ ). XiSpec with green LED illumination gave the expected change in /RBC , while the dynamics in ^S0₂ were less than those for EPOS. These results may be explained by the calculation of modulation using an illumination and detector setup with a broad spectral transmission bandwidth, with considerable variation in μ_a of included chromophores. Approaches for either reducing the effective bandwidth of the XiSpec filters or by including their characteristic in a light transport model for SFDI modulation, are proposed.

Proceedings Article | 19 February 2018 Open Access

Open Access

Paper

hyperspectral characterization of tissue simulating phantoms using a supercontinuum laser in a spatial frequency domain imaging instrument

Mohammad Torabzadeh, Patrick Stockton, Gordon Kennedy, Rolf Saager, Anthony Durkin, Randy Bartels, Bruce Tromberg

Proceedings Volume 10486, 104860G (2018) https://doi.org/10.1117/12.2291369

KEYWORDS: Absorption, Cameras, Scattering, Tissue optics, Optical properties, Supercontinuum sources, Diffuse optical spectroscopy

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SPIE Journal Paper | 20 July 2017 Open Access

Open Access

Solid tissue simulating phantoms having absorption at 970 nm for diffuse optics

Gordon Kennedy, Griffin Lentsch, Brandon Trieu, Adrien Ponticorvo, Rolf Saager, Anthony Durkin

JBO, Vol. 22, Issue 07, 076013, (July 2017) https://doi.org/10.1117/12.10.1117/1.JBO.22.7.076013

KEYWORDS: Tissue optics, Solids, Tissues, Absorption, Diffuse optical imaging, Scattering, Optical simulations, Optical components, Luminescence, Chromophores

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Proceedings Article | 14 March 2017 Paper

Paper

Design and fabrication of solid phantoms for NIR water fraction studies

Gordon Kennedy, Griffin Lentsch, Brandon Trieu, Adrien Ponticorvo, Rolf Saager, Anthony Durkin

Proceedings Volume 10056, 100560A (2017) https://doi.org/10.1117/12.2250672

KEYWORDS: Absorption, Tissues, Near infrared, Tissue optics, Scattering, Biomedical optics, Diffuse optical imaging, Water, Silicon, Optical properties

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Proceedings Article | 27 April 2016 Presentation

Presentation

Quantitative long term measurements of burns in a rat model using spatial frequency domain imaging and laser speckle imaging (Conference Presentation)

Adrien Ponticorvo, Rebecca Rowland, Melissa Baldado, Gordon Kennedy, Rolf Saager, Bernard Choi, Anthony Durkin

Proceedings Volume 9711, 971102 (2016) https://doi.org/10.1117/12.2214080

KEYWORDS: Injuries, Laser speckle imaging, Wound healing, Speckle imaging, Optical inspection, Biopsy, Visualization, Inflammation, Scattering, Scatter measurement

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Proceedings Article | 26 April 2016 Open Access

Open Access

Presentation

From theory to practice: the broadening role of polydimethylsiloxane phantoms as an intermediary between model validation and instrument performance testing (Conference Presentation)

Rolf Saager, Alan Quach, Gordon Kennedy, Bruce Tromberg, Anthony Durkin

Proceedings Volume 9700, 97000G (2016) https://doi.org/10.1117/12.2218388

KEYWORDS: Instrument modeling, Performance modeling, Tissue optics, Optical phantoms, Optical fabrication, Optical simulations, Calibration, Optical fabrication equipment, Light scattering, Laser scattering

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Proceedings Article | 22 February 2011 Paper

Paper

Fluorescence lifetime imaging endoscopy

G. Kennedy, S. Coda, A. Thompson, D. Elson, M. A. Neil, G. Stamp, A. Thillainayagam, B. Viellerobe, F. Lacombe, C. Dunsby, Paul M. French

Proceedings Volume 7893, 789308 (2011) https://doi.org/10.1117/12.874968

KEYWORDS: Fluorescence lifetime imaging, Endoscopes, Luminescence, Confocal microscopy, Endoscopy, Tissues, Biopsy, In vivo imaging, Tissue optics, Fluorescence resonance energy transfer

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Proceedings Article | 17 February 2011 Paper

Paper

Hyperspectral fluorescence lifetime fibre probe spectroscopy for use in the study and diagnosis of osteoarthritis and skin cancer

Alex Thompson, Hugh Manning, Mikkel Brydegaard, Sergio Coda, Gordon Kennedy, Rakesh Patalay, Ulrika Waitong-Braemming, Pieter De Beule, Mark Neil, Stefan Andersson-Engels, Yoshifumi Itoh, Niels Bendsøe, Christopher Dunsby, Katarina Svanberg, Paul M. French

Proceedings Volume 7895, 78950G (2011) https://doi.org/10.1117/12.875120

KEYWORDS: Luminescence, Spectroscopy, Cartilage, Skin cancer, Tissues, In vivo imaging, Collagen, Tissue optics, Reflectivity, Diffuse reflectance spectroscopy

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Proceedings Article | 14 February 2007 Paper

Paper

Microscopy using micropixellated light emitting diodes

V. Poher, G. Kennedy, D. Elson, P. French, M. Neil, H. Z. Zhang, E. Gu, Z. Gong, C. Griffin, J. Girkin, M. Dawson

Proceedings Volume 6443, 644313 (2007) https://doi.org/10.1117/12.700811

KEYWORDS: Light emitting diodes, Microscopy, Confocal microscopy, Microscopes, Light sources, Line scan image sensors, Luminescence, Solid state electronics, CCD cameras, Cameras

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Proceedings Article | 14 February 2007 Paper

Paper

Fluorescence lifetime imaging using light-emitting diodes

Gordon Kennedy, Daniel Elson, Ian Munro, Vincent Poher, Paul French, Mark Neil

Proceedings Volume 6443, 644315 (2007) https://doi.org/10.1117/12.701088

KEYWORDS: Light emitting diodes, Fluorescence lifetime imaging, Luminescence, Modulation, Picosecond phenomena, Microscopy, LED lighting, Digital filtering, Light sources and illumination, Confocal microscopy

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Showing 5 of 41 publications

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