Volume 29 Issue 1 | Journal of Biomedical Optics

Journal of Biomedical Optics

VOL. 29 · NO. 1 | January 2024

CONTENTS

IN THIS ISSUE

Editorial (1)

Review Papers (1)

General (4)

Imaging (10)

Microscopy (1)

Sensing (2)

Therapeutic (1)

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Editorial

JBO 2023 List of Reviewers

Journal of Biomedical Optics, Vol. 29, Issue 01, 010102, (January 2024) https://doi.org/10.1117/1.JBO.29.1.010102

TOPICS: Lithium, Chaos, Sun, Silicon, Lutetium, Germanium, Content addressable memory, Bismuth

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Review Papers

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

Kerry Setchfield, Alistair Gorman, A. Hamish R. Simpson, Michael Somekh, Amanda Wright

Journal of Biomedical Optics, Vol. 29, Issue 01, 010901, (January 2024) https://doi.org/10.1117/1.JBO.29.1.010901

TOPICS: Skin, Optical properties, Absorption, Light scattering, Tissue optics, Color, Light absorption, Optical coherence tomography, Biomedical optics, Scattering

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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.

General

Designing a use-error robust machine learning model for quantitative analysis of diffuse reflectance spectra

Allison Scarbrough, Keke Chen, Bing Yu

Journal of Biomedical Optics, Vol. 29, Issue 01, 015001, (January 2024) https://doi.org/10.1117/1.JBO.29.1.015001

TOPICS: Data modeling, RGB color model, Education and training, Machine learning, Optical properties, Monte Carlo methods, Performance modeling, Computer simulations, Feature extraction, Diffuse reflectance spectroscopy

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HyperTRCSS: A hyperspectral time-resolved compressive sensing spectrometer for depth-sensitive monitoring of cytochrome-c-oxidase and blood oxygenation

Natalie Li, Seva Ioussoufovitch, Mamadou Diop

Journal of Biomedical Optics, Vol. 29, Issue 01, 015002, (January 2024) https://doi.org/10.1117/1.JBO.29.1.015002

TOPICS: Spectroscopy, Simulations, Oxygenation, Blood, Chromophores, Error analysis, Windows, Signal to noise ratio, Oxygen, Photons

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Quantitative photothermal analysis and multispectral imaging of dental structures: insights into optical and thermal properties of carious and healthy teeth

Elnaz Baradaran Shokouhi, Damber Thapa, Robert Welch, Koneswaran Sivagurunathan, Andreas Mandelis

Journal of Biomedical Optics, Vol. 29, Issue 01, 015003, (January 2024) https://doi.org/10.1117/1.JBO.29.1.015003

TOPICS: Enamels, Teeth, Thermography, Optical parametric oscillators, Semiconductor lasers, Multispectral imaging, Scattering, Tissues, Laser scattering, Dental caries

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Significance

In the analysis of two-layered turbid dental tissues, the outer finite-thickness layer is modeled by an optical transport coefficient distinct from its underlying semi-infinite substrate layer. The optical and thermophysical parameters of healthy and carious teeth across the various wavelengths were measured leading to the determination of the degree of reliability of each of the fitted parameters, with most reliable being thermal diffusivity and conductivity, enamel thickness, and optical transport coefficient of the enamel layer. Quantitative pixel-by-pixel images of the key reliable optical and thermophysical parameters were constructed.

Aim

We introduced a theoretical model of pulsed photothermal radiometry based on conduction-radiation theory and applied to quantitative photothermal detection and imaging of biomaterials. The theoretical model integrates a combination of inverse Fourier transformation techniques, avoiding the conventional cumbersome analytical Laplace transform method.

Approach

Two dental samples were selected for analysis: the first sample featured controlled, artificially induced early caries on a healthy tooth surface, while the second sample exhibited natural defects along with an internal filling. Using an Nd:YAG laser and specific optical parametric oscillator (OPO) wavelengths (675, 700, 750, and 808 nm), photothermal transient signals were captured from different points on these teeth and analyzed as a function of OPO wavelength. Measurements were also performed with an 808-nm laser diode for comparison with the same OPO wavelength excitation, particularly for the second sample with natural defects.

Results

The findings demonstrated that the photothermal transient signals exhibit a fast-decaying pattern at shorter wavelengths due to their higher scattering nature, while increased scattering and absorption in the carious regions masked conductive and radiative contributions from the underlayer. These observations were cross-validated using micro-computed tomography, which also enabled the examination of signal patterns at different tooth locations.

Conclusions

The results of our study showed the impact of optical and thermal characteristics of two-layered turbid dental tissues via an inverse Fourier technique, as well as the interactions between these layers, on the patterns observed in depth profiles.

Quantification of blood flow index in diffuse correlation spectroscopy using a robust deep learning method

Quan Wang, Mingliang Pan, Zhenya Zang, David Li

Journal of Biomedical Optics, Vol. 29, Issue 01, 015004, (January 2024) https://doi.org/10.1117/1.JBO.29.1.015004

TOPICS: Blood circulation, Analytic models, Education and training, Spectroscopy, Data modeling, Brain, Skull, Error analysis, Optical properties, Monte Carlo methods

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Significance

Diffuse correlation spectroscopy (DCS) is a powerful, noninvasive optical technique for measuring blood flow. Traditionally the blood flow index (BFi) is derived through nonlinear least-square fitting the measured intensity autocorrelation function (ACF). However, the fitting process is computationally intensive, susceptible to measurement noise, and easily influenced by optical properties (absorption coefficient μa and reduced scattering coefficient μs′) and scalp and skull thicknesses.

Aim

We aim to develop a data-driven method that enables rapid and robust analysis of multiple-scattered light’s temporal ACFs. Moreover, the proposed method can be applied to a range of source–detector distances instead of being limited to a specific source–detector distance.

Approach

We present a deep learning architecture with one-dimensional convolution neural networks, called DCS neural network (DCS-NET), for BFi and coherent factor (β) estimation. This DCS-NET was performed using simulated DCS data based on a three-layer brain model. We quantified the impact from physiologically relevant optical property variations, layer thicknesses, realistic noise levels, and multiple source–detector distances (5, 10, 15, 20, 25, and 30 mm) on BFi and β estimations among DCS-NET, semi-infinite, and three-layer fitting models.

Results

DCS-NET shows a much faster analysis speed, around 17,000-fold and 32-fold faster than the traditional three-layer and semi-infinite models, respectively. It offers higher intrinsic sensitivity to deep tissues compared with fitting methods. DCS-NET shows excellent anti-noise features and is less sensitive to variations of μa and μs′ at a source–detector separation of 30 mm. Also, we have demonstrated that relative BFi (rBFi) can be extracted by DCS-NET with a much lower error of 8.35%. By contrast, the semi-infinite and three-layer fitting models result in significant errors in rBFi of 43.76% and 19.66%, respectively.

Conclusions

DCS-NET can robustly quantify blood flow measurements at considerable source–detector distances, corresponding to much deeper biological tissues. It has excellent potential for hardware implementation, promising continuous real-time blood flow measurements.

Imaging

Automatic correction of motion artifact in dynamic contrast-enhanced fluorescence imaging during open orthopedic surgery

Yue Tang, Ida Leah Gitajn, Xu Cao, Xinyue Han, Jonathan Elliott, Logan Bateman, Bethany Malskis, Lillian Fisher, Jessica Sin, Eric Henderson, Shudong Jiang

Journal of Biomedical Optics, Vol. 29, Issue 01, 016001, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016001

TOPICS: Bone, Fluorescence imaging, Biological imaging, Fluorescence intensity, Surgery, Imaging systems, Tissues, Fluorescence, Histograms, Perfusion imaging

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Optical coherence elastography measures the biomechanical properties of the ex vivo porcine cornea after LASIK

Achuth Nair, Fernando Zvietcovich, Manmohan Singh, Mitchell P. Weikert, Salavat R. Aglyamov, Kirill V. Larin

Journal of Biomedical Optics, Vol. 29, Issue 01, 016002, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016002

TOPICS: Cornea, LASIK, Biomechanics, Eye, Tissues, Elastography, Surgery, Optical coherence tomography, Laser ablation, Optical coherence

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Improved intraoperative identification of close margins in oral squamous cell carcinoma resections using a dual aperture fluorescence ratio approach: first in-human results

Cody C. Rounds, Jaron G. de Wit, Jasper Vonk, Jennifer Vorjohan, Sophia Nelson, Allyson Trang, Brooke Villinski, Kimberley S. Samkoe, Jovan G. Brankov, Floris J. Voskuil, Max J. H. Witjes, Kenneth M. Tichauer

Journal of Biomedical Optics, Vol. 29, Issue 01, 016003, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016003

TOPICS: Fluorescence, Resection, Tumors, Surgery, Imaging systems, Statistical analysis, Pathology, Cancer detection, Fluorescence imaging, Tissues

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Subsurface fluorescence time-of-flight imaging using a large-format single-photon avalanche diode sensor for tumor depth assessment

Arthur F. Petusseau, Samuel S. Streeter, Arin Ulku, Yichen Feng, Kimberley S. Samkoe, Claudio Bruschini, Edoardo Charbon, Brian W. Pogue, Petr Bruza

Journal of Biomedical Optics, Vol. 29, Issue 01, 016004, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016004

TOPICS: Fluorescence, Tissues, Reflectivity, Optical properties, Single photon avalanche diodes, Fluorescence intensity, Calibration, Tumors, Time of flight imaging, Gelatin

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Significance

Fluorescence guidance is used clinically by surgeons to visualize anatomical and/or physiological phenomena in the surgical field that are difficult or impossible to detect by the naked eye. Such phenomena include tissue perfusion or molecular phenotypic information about the disease being resected. Conventional fluorescence-guided surgery relies on long, microsecond scale laser pulses to excite fluorescent probes. However, this technique only provides two-dimensional information; crucial depth information, such as the location of malignancy below the tissue surface, is not provided.

Aim

We developed a depth sensing imaging technique using light detection and ranging (LiDAR) time-of-flight (TOF) technology to sense the depth of target tissue while overcoming the influence of tissue optical properties and fluorescent probe concentration.

Approach

The technology is based on a large-format (512×512 pixel), binary, gated, single-photon avalanche diode (SPAD) sensor with an 18 ps time-gate step, synchronized with a picosecond pulsed laser. The fast response of the sensor was developed and tested for its ability to quantify fluorescent inclusions at depth and optical properties in tissue-like phantoms through analytical model fitting of the fast temporal remission data.

Results

After calibration and algorithmic extraction of the data, the SPAD LiDAR technique allowed for sub-mm resolution depth sensing of fluorescent inclusions embedded in tissue-like phantoms, up to a maximum of 5 mm in depth. The approach provides robust depth sensing even in the presence of variable tissue optical properties and separates the effects of fluorescence depth from absorption and scattering variations.

Conclusions

LiDAR TOF fluorescence imaging using an SPAD camera provides both fluorescence intensity images and the temporal profile of fluorescence, which can be used to determine the depth at which the signal is emitted over a wide field of view. The proposed tool enables fluorescence imaging at a higher depth in tissue and with higher spatial precision than standard, steady-state fluorescence imaging tools, such as intensity-based near-infrared fluorescence imaging, optical coherence tomography, Raman spectroscopy, or confocal microscopy. Integration of this technique into a standard surgical tool could enable rapid, more accurate estimation of resection boundaries, thereby improving the surgeon’s efficacy and efficiency, and ultimately improving patient outcomes.

Polarized hyperspectral microscopic imaging system for enhancing the visualization of collagen fibers and head and neck squamous cell carcinoma

Ximing Zhou, Ling Ma, Hasan Mubarak, Doreen Palsgrove, Baran Sumer, Amy Chen, Baowei Fei

Journal of Biomedical Optics, Vol. 29, Issue 01, 016005, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016005

TOPICS: Tumors, Collagen, RGB color model, Hyperspectral imaging, Tissues, Imaging systems, Visualization, Microscopes, Neck, Head

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Significance

Polarized hyperspectral microscopes with the capability of full Stokes vector imaging have potential for many biological and medical applications.

Aim

The aim of this study is to investigate polarized hyperspectral imaging (PHSI) for improving the visualization of collagen fibers, which is an important biomarker related to tumor development, and improving the differentiation of normal and tumor cells on pathologic slides.

Approach

We customized a polarized hyperspectral microscopic imaging system comprising an upright microscope with a motorized stage, two linear polarizers, two liquid crystal variable retarders (LCVRs), and a compact SnapScan hyperspectral camera. The polarizers and LCVRs worked in tandem with the hyperspectral camera to acquire polarized hyperspectral images, which were further used to calculate four Stokes vectors: S0, S1, S2, and S3. Synthetic RGB images of the Stokes vectors were generated for the visualization of cellular components in PHSI images. Regions of interest of collagen, normal cells, and tumor cells in the synthetic RGB images were selected, and spectral signatures of the selected components were extracted for comparison. Specifically, we qualitatively and quantitatively investigated the enhanced visualization and spectral characteristics of dense fibers and sparse fibers in normal stroma tissue, fibers accumulated within tumors, and fibers accumulated around tumors.

Results

By employing our customized polarized hyperspectral microscope, we extract the spectral signatures of Stokes vector parameters of collagen as well as of tumor and normal cells. The measurement of Stokes vector parameters increased the image contrast of collagen fibers and cells in the slides.

Conclusions

With the spatial and spectral information from the Stokes vector data cubes (S0, S1, S2, and S3), our PHSI microscope system enhances the visualization of tumor cells and tumor microenvironment components, thus being beneficial for pathology and oncology.

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

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

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

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Significance

We 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.

Aim

Our 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.

Approach

We 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.

Results

The 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.

Conclusions

We demonstrated the potential for motion-resistant three-wavelength SFDI system with ambient light suppression using an 8-tap CIS.

Combined flat-field and frequency filter approach to correcting artifacts of multichannel two-photon microscopy

Thomas Knapp, Natzem Lima, Noelle Daigle, Suzann Duan, Juanita L. Merchant, Travis Sawyer

Journal of Biomedical Optics, Vol. 29, Issue 01, 016007, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016007

TOPICS: Image processing, Tunable filters, Tissues, Image filtering, Image quality, Vignetting, Image fusion, Biological samples, Fourier transforms, Autofluorescence

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Discrimination of lipid composition and cellular localization in human liver tissues by stimulated Raman scattering microscopy

Fiona Xi Xu, George Ioannou, Sum Lee, Christopher Savard, Christian Horn, Dan Fu

Journal of Biomedical Optics, Vol. 29, Issue 01, 016008, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016008

TOPICS: Tissues, Liver, Molecules, Microscopy, Crystals, Polarization, Imaging systems, Body composition, Hyperspectral imaging, Raman spectroscopy

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Wide dynamic range measurement of blood flow in vivo using laser speckle contrast imaging

Hong Li Liu, Yuan Yuan, Li Han, Yong Bi, Wen Yuan Yu, Yang Yu

Journal of Biomedical Optics, Vol. 29, Issue 01, 016009, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016009

TOPICS: Blood circulation, Laser speckle contrast imaging, Arteries, Speckle, In vivo imaging, Veins, Animals, Speckle pattern, Scattering, Biological imaging

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TIE-GANs: single-shot quantitative phase imaging using transport of intensity equation with integration of GANs

Vikas Thapa, Ashwini Galande, Gurram Hanu Phani Ram, Renu John

Journal of Biomedical Optics, Vol. 29, Issue 01, 016010, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016010

TOPICS: Education and training, Gallium nitride, Phase reconstruction, Phase imaging, Image restoration, Microscopes, Data modeling, Biomedical optics, Phase retrieval, Biological samples

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Significance

Artificial intelligence (AI) has become a prominent technology in computational imaging over the past decade. The expeditious and label-free characteristics of quantitative phase imaging (QPI) render it a promising contender for AI investigation. Though interferometric methodologies exhibit potential efficacy, their implementation involves complex experimental platforms and computationally intensive reconstruction procedures. Hence, non-interferometric methods, such as transport of intensity equation (TIE), are preferred over interferometric methods.

Aim

TIE method, despite its effectiveness, is tedious as it requires the acquisition of many images at varying defocus planes. The proposed methodology holds the ability to generate a phase image utilizing a single intensity image using generative adversarial networks (GANs). We present a method called TIE-GANs to overcome the multi-shot scheme of conventional TIE.

Approach

The present investigation employs the TIE as a QPI methodology, which necessitates reduced experimental and computational efforts. TIE is being used for the dataset preparation as well. The proposed method captures images from different defocus planes for training. Our approach uses an image-to-image translation technique to produce phase maps and is based on GANs. The main contribution of this work is the introduction of GANs with TIE (TIE:GANs) that can give better phase reconstruction results with shorter computation times. This is the first time the GANs is proposed for TIE phase retrieval.

Results

The characterization of the system was carried out with microbeads of 4 μm size and structural similarity index (SSIM) for microbeads was found to be 0.98. We demonstrated the application of the proposed method with oral cells, which yielded a maximum SSIM value of 0.95. The key characteristics include mean squared error and peak-signal-to-noise ratio values of 140 and 26.42 dB for oral cells and 100 and 28.10 dB for microbeads.

Conclusions

The proposed methodology holds the ability to generate a phase image utilizing a single intensity image. Our method is feasible for digital cytology because of its reported high value of SSIM. Our approach can handle defocused images in such a way that it can take intensity image from any defocus plane within the provided range and able to generate phase map.

Microscopy

Rapid, high-contrast, and steady volumetric imaging with Bessel-beam-based two-photon fluorescence microscopy

Yongqiang Chen, Chenggui Luo, Shiqi Wang, Yanping Li, Binglin Shen, Rui Hu, Junle Qu, Liwei Liu

Journal of Biomedical Optics, Vol. 29, Issue 01, 016501, (January 2024) https://doi.org/10.1117/1.JBO.29.1.016501

TOPICS: Bessel beams, Imaging systems, Biological imaging, In vivo imaging, Biomedical optics, Fluorescence imaging, Spatial light modulators, Image processing, Brain, 3D image processing

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Sensing

Non-invasive assessment of sublingual microcirculation using flow derived from green light PPG: evaluation and reference values

Rafael Uribe Acevedo, Laura Osorio Sánchez, Sebastián Vergara Londoño, Elisa Mejía-Mejía, Róbinson Torres Villa, Yesid Montoya Goez

Journal of Biomedical Optics, Vol. 29, Issue 01, 017001, (January 2024) https://doi.org/10.1117/1.JBO.29.1.017001

TOPICS: Sensors, Tongue, Tissues, Signal detection, Feature extraction, Capillaries, Blood circulation, Reflection, Tunable filters, Signal processing

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Development of a cost-effective compact diode-laser-based photoacoustic sensing instrument for breast tissue diagnosis

Suhel Khan, Sramana Mukhopadhyay, Srivathsan Vasudevan, Garima Goel, Deepti Joshi, Neelkamal Kapoor, Saikat Das

Journal of Biomedical Optics, Vol. 29, Issue 01, 017002, (January 2024) https://doi.org/10.1117/1.JBO.29.1.017002

TOPICS: Tissues, Semiconductor lasers, Breast, Biological samples, Diseases and disorders, Laser frequency, Laser development, Equipment, Pulsed laser operation, Design

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Therapeutic

Clinical PDT dose dosimetry for pleural Photofrin-mediated photodynamic therapy

Hongjing Sun, Yihong Ong, Weibing Yang, Dennis Sourvanos, Andreea Dimofte, Theresa M. Busch, Sunil Singhal, Keith A. Cengel, Timothy C. Zhu

Journal of Biomedical Optics, Vol. 29, Issue 01, 018001, (January 2024) https://doi.org/10.1117/1.JBO.29.1.018001

TOPICS: Photodynamic therapy, Dosimetry, Picosecond phenomena, Fluorescence, Optical properties, Tissues, Navigation systems, Sensors, Optical testing, Singular value decomposition

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Significance

Photodynamic therapy (PDT) is an established cancer treatment utilizing light-activated photosensitizers (PS). Effective treatment hinges on the PDT dose-dependent on PS concentration and light fluence-delivered over time. We introduce an innovative eight-channel PDT dose dosimetry system capable of concurrently measuring light fluence and PS concentration during treatment.

Aim

We aim to develop and evaluate an eight-channel PDT dose dosimetry system for simultaneous measurement of light fluence and PS concentration. By addressing uncertainties due to tissue variations, the system enhances accurate PDT dosimetry for improved treatment outcomes.

Approach

The study positions eight isotropic detectors strategically within the pleural cavity before PDT. These detectors are linked to bifurcated fibers, distributing signals to both a photodiode and a spectrometer. Calibration techniques are applied to counter tissue-related variations and improve measurement accuracy. The fluorescence signal is normalized using the measured light fluence, compensating for variations in tissue properties. Measurements were taken in 78 sites in the pleural cavities of 20 patients.

Results

Observations reveal minimal Photofrin concentration variation during PDT at each site, juxtaposed with significant intra- and inter-patient heterogeneities. Across 78 treated sites in 20 patients, the average Photofrin concentration for all 78 sites is 4.98 μM, with a median concentration of 4.47 μM. The average PDT dose for all 78 sites is 493.17 μMJ/cm2, with a median dose of 442.79 μMJ/cm2. A significant variation in PDT doses is observed, with a maximum difference of 3.1 times among all sites within one patient and a maximum difference of 9.8 times across all patients.

Conclusions

The introduced eight-channel PDT dose dosimetry system serves as a valuable real-time monitoring tool for light fluence and PS concentration during PDT. Its ability to mitigate uncertainties arising from tissue properties enhances dosimetry accuracy, thus optimizing treatment outcomes and bolstering the effectiveness of PDT in cancer therapy.