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Crowley J, Gordon GSD. Ultra-miniature dual-wavelength spatial frequency domain imaging for micro-endoscopy. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:026002. [PMID: 38312854 PMCID: PMC10832795 DOI: 10.1117/1.jbo.29.2.026002] [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: 06/07/2023] [Revised: 11/08/2023] [Accepted: 11/14/2023] [Indexed: 02/06/2024]
Abstract
Significance There is a need for a cost-effective, quantitative imaging tool that can be deployed endoscopically to better detect early stage gastrointestinal cancers. Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that produces near-real time, quantitative maps of absorption and reduced scattering coefficients, but most implementations are bulky and suitable only for use outside the body. Aim We aim to develop an ultra-miniature SFDI system comprising an optical fiber array (diameter 0.125 mm) and a micro camera (1 × 1 mm package) to displace conventionally bulky components, in particular, the projector. Approach First, we fabricated a prototype with an outer diameter of 3 mm, although the individual component dimensions could permit future packaging to a < 1.5 mm diameter. We developed a phase-tracking algorithm to rapidly extract images with fringe projections at three equispaced phase shifts to perform SFDI demodulation. Results To validate the performance, we first demonstrate comparable recovery of quantitative optical properties between our ultra-miniature system and a conventional bench-top SFDI system with an agreement of 15% and 6% for absorption and reduced scattering, respectively. Next, we demonstrate imaging of absorption and reduced scattering of tissue-mimicking phantoms providing enhanced contrast between simulated tissue types (healthy and tumour), done simultaneously at wavelengths of 515 and 660 nm. Using a support vector machine classifier, we estimate that sensitivity and specificity values of > 90 % are feasible for detecting simulated squamous cell carcinoma. Conclusions This device shows promise as a cost-effective, quantitative imaging tool to detect variations in optical absorption and scattering as indicators of cancer.
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Affiliation(s)
- Jane Crowley
- University of Nottingham, Department of Electrical and Electronic Engineering, Optics and Photonics Group, Nottingham, United Kingdom
| | - George S. D. Gordon
- University of Nottingham, Department of Electrical and Electronic Engineering, Optics and Photonics Group, Nottingham, United Kingdom
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2
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Crowley J, Gordon GSD. Designing and simulating realistic spatial frequency domain imaging systems using open-source 3D rendering software. BIOMEDICAL OPTICS EXPRESS 2023; 14:2523-2538. [PMID: 37342713 PMCID: PMC10278632 DOI: 10.1364/boe.484286] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 04/24/2023] [Accepted: 04/25/2023] [Indexed: 06/23/2023]
Abstract
Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that maps absorption and reduced scattering coefficients, offering improved contrast for important tissue structures such as tumours. Practical SFDI systems must cope with various imaging geometries including imaging planar samples ex vivo, imaging inside tubular lumen in vivo e.g. for endoscopy, and measuring tumours or polyps of varying morphology. There is a need for a design and simulation tool to accelerate design of new SFDI systems and simulate realistic performance under these scenarios. We present such a system implemented using open-source 3D design and ray-tracing software Blender that simulates media with realistic absorption and scattering in a wide range of geometries. By using Blender's Cycles ray-tracing engine, our system simulates effects such as varying lighting, refractive index changes, non-normal incidence, specular reflections and shadows, enabling realistic evaluation of new designs. We first demonstrate quantitative agreement between Monte-Carlo simulated absorption and reduced scattering coefficients with those simulated from our Blender system, achieving 16 % discrepancy in absorption coefficient and 18 % in reduced scattering coefficient. However, we then show that using an empirically derived look-up table the errors reduce to 1 % and 0.7 % respectively. Next, we simulate SFDI mapping of absorption, scattering and shape for simulated tumour spheroids, demonstrating enhanced contrast. Finally we demonstrate SFDI mapping inside a tubular lumen, which highlighted a important design insight: custom look-up tables must be generated for different longitudinal sections of the lumen. With this approach we achieved 2 % absorption error and 2 % scattering error. We anticipate our simulation system will aid in the design of novel SFDI systems for key biomedical applications.
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Affiliation(s)
- Jane Crowley
- Optics & Photonics Group, Department of Electrical and
Electronic Engineering, University of Nottingham, Nottingham, United
Kingdom
| | - George S. D. Gordon
- Optics & Photonics Group, Department of Electrical and
Electronic Engineering, University of Nottingham, Nottingham, United
Kingdom
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3
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Pilvar A, Mehendale AM, Karrobi K, El-Adili F, Bujor A, Roblyer D. Spatial frequency domain imaging for the assessment of scleroderma skin involvement. BIOMEDICAL OPTICS EXPRESS 2023; 14:2955-2968. [PMID: 37342706 PMCID: PMC10278615 DOI: 10.1364/boe.489609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/11/2023] [Accepted: 05/11/2023] [Indexed: 06/23/2023]
Abstract
Systemic sclerosis (SSc) is an autoimmune disease characterized by the widespread deposition of excess collagen in the skin and internal organs, as well as vascular dysfunction. The current standard of care technique used to quantify the extent of skin fibrosis in SSc patients is the modified Rodnan skin score (mRSS), which is an assessment of skin thickness based on clinical palpation. Despite being considered the gold standard, mRSS testing requires a trained physician and suffers from high inter-observer variability. In this study, we evaluated the use of spatial frequency domain imaging (SFDI) as a more quantitative and reliable method for assessing skin fibrosis in SSc patients. SFDI is a wide-field and non-contact imaging technique that utilizes spatially modulated light to generate a map of optical properties in biological tissue. The SFDI data were collected at six measurement sites (left and right forearms, hands, and fingers) of eight control subjects and ten SSc patients. mRSS were assessed by a physician, and skin biopsies were collected from subject's forearms and used to assess for markers of skin fibrosis. Our results indicate that SFDI is sensitive to skin changes even at an early stage, as we found a significant difference in the measured optical scattering (μs') between healthy controls and SSc patients with a local mRSS score of zero (no appreciable skin fibrosis by gold standard). Furthermore, we found a strong correlation between the diffuse reflectance (Rd) at a spatial frequency of 0.2 mm-1 and the total mRSS between all subjects (Spearman correlation coefficient = -0.73, p-value < 0.0028), as well as high correlation with histology results. The healthy volunteer results show excellent inter- and intra-observer reliability (ICC > 0.8). Our results suggest that the measurement of tissue μs' and Rd at specific spatial frequencies and wavelengths can provide an objective and quantitative assessment of skin involvement in SSc patients, which could greatly improve the accuracy and efficiency of monitoring disease progression and evaluating drug efficacy.
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Affiliation(s)
- Anahita Pilvar
- Department of Electrical and Computer Engineering, Boston University, Boston, MA 02215, USA
| | - Aarohi M. Mehendale
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Kavon Karrobi
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Fatima El-Adili
- Division of Rheumatology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
- Arthritis and Autoimmune Diseases Center, Boston University, Boston, MA 02118, USA
| | - Andreea Bujor
- Division of Rheumatology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
- Arthritis and Autoimmune Diseases Center, Boston University, Boston, MA 02118, USA
| | - Darren Roblyer
- Department of Electrical and Computer Engineering, Boston University, Boston, MA 02215, USA
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
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4
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Tran MH, Fei B. Compact and ultracompact spectral imagers: technology and applications in biomedical imaging. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:040901. [PMID: 37035031 PMCID: PMC10075274 DOI: 10.1117/1.jbo.28.4.040901] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 02/27/2023] [Indexed: 05/18/2023]
Abstract
Significance Spectral imaging, which includes hyperspectral and multispectral imaging, can provide images in numerous wavelength bands within and beyond the visible light spectrum. Emerging technologies that enable compact, portable spectral imaging cameras can facilitate new applications in biomedical imaging. Aim With this review paper, researchers will (1) understand the technological trends of upcoming spectral cameras, (2) understand new specific applications that portable spectral imaging unlocked, and (3) evaluate proper spectral imaging systems for their specific applications. Approach We performed a comprehensive literature review in three databases (Scopus, PubMed, and Web of Science). We included only fully realized systems with definable dimensions. To best accommodate many different definitions of "compact," we included a table of dimensions and weights for systems that met our definition. Results There is a wide variety of contributions from industry, academic, and hobbyist spaces. A variety of new engineering approaches, such as Fabry-Perot interferometers, spectrally resolved detector array (mosaic array), microelectro-mechanical systems, 3D printing, light-emitting diodes, and smartphones, were used in the construction of compact spectral imaging cameras. In bioimaging applications, these compact devices were used for in vivo and ex vivo diagnosis and surgical settings. Conclusions Compact and ultracompact spectral imagers are the future of spectral imaging systems. Researchers in the bioimaging fields are building systems that are low-cost, fast in acquisition time, and mobile enough to be handheld.
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Affiliation(s)
- Minh H. Tran
- University of Texas at Dallas, Department of Bioengineering, Richardson, Texas, United States
| | - Baowei Fei
- University of Texas at Dallas, Department of Bioengineering, Richardson, Texas, United States
- University of Texas Southwestern Medical Center, Department of Radiology, Dallas, Texas, United States
- University of Texas at Dallas, Center for Imaging and Surgical Innovation, Richardson, Texas, United States
- Address all correspondence to Baowei Fei,
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5
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Lam JH, Tu KJ, Kim J, Kim S. Smartphone-based single snapshot spatial frequency domain imaging. BIOMEDICAL OPTICS EXPRESS 2022; 13:6497-6507. [PMID: 36589565 PMCID: PMC9774861 DOI: 10.1364/boe.470665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/30/2022] [Accepted: 11/03/2022] [Indexed: 06/17/2023]
Abstract
We report a handheld, smartphone-based spatial frequency domain imaging device. We first examined the linear dynamic range of the smartphone camera sensor. We then calculated optical properties for a series of liquid phantoms with varying concentrations of nigrosin ink and Intralipid, demonstrating separation of absorption and scattering. The device was then tested on a human wrist, where optical properties and hemoglobin-based chromophores were calculated. Finally, we performed an arterial occlusion on a human hand and captured hemodynamics using our device. We hope to lay the foundation for an accessible SFDI device with mass-market appeal designed for dermatological and cosmetic applications.
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Affiliation(s)
- Jesse H. Lam
- Dankook University, Beckman Laser Institute Korea, School of Medicine, Cheonan, Chungnam, Republic of Korea
| | - Kelsey J. Tu
- Dankook University, Department of Biomedical Engineering, Cheonan, Chungnam, Republic of Korea
| | - Jeonghun Kim
- Dankook University, Department of Biomedical Engineering, Cheonan, Chungnam, Republic of Korea
- MEDiThings Co. Ltd., Industry-Academia Cooperation, Dankook University, Cheonan, Chungnam, Republic of Korea
| | - Sehwan Kim
- Dankook University, Department of Biomedical Engineering, Cheonan, Chungnam, Republic of Korea
- University of California, Irvine, Beckman Laser Institute, Department of Biomedical Engineering, Irvine, CA, USA
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Majedy M, Das NK, Johansson J, Saager RB. Influence of optical aberrations on depth-specific spatial frequency domain techniques. JOURNAL OF BIOMEDICAL OPTICS 2022; 27:116003. [PMID: 36358008 PMCID: PMC9646941 DOI: 10.1117/1.jbo.27.11.116003] [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: 08/04/2022] [Accepted: 10/24/2022] [Indexed: 06/16/2023]
Abstract
SIGNIFICANCE Spatial frequency domain imaging (SFDI) and spatial frequency domain spectroscopy (SFDS) are emerging tools to non-invasively assess tissues. However, the presence of aberrations can complicate processing and interpretation. AIM This study develops a method to characterize optical aberrations when performing SFDI/S measurements. Additionally, we propose a post-processing method to compensate for these aberrations and recover arbitrary subsurface optical properties. APPROACH Using a custom SFDS system, we extract absorption and scattering coefficients from a reference phantom at 0 to 15 mm distances from the ideal focus. In post-processing, we characterize aberrations in terms of errors in absorption and scattering relative to the expected in-focus values. We subsequently evaluate a compensation approach in multi-distance measurements of phantoms with different optical properties and in multi-layer phantom constructs to mimic subsurface targets. RESULTS Characterizing depth-specific aberrations revealed a strong power law such as wavelength dependence from ∼40 to ∼10 % error in both scattering and absorption. When applying the compensation method, scattering remained within 1.3% (root-mean-square) of the ideal values, independent of depth or top layer thickness, and absorption remained within 3.8%. CONCLUSIONS We have developed a protocol that allows for instrument-specific characterization and compensation for the effects of defocus and chromatic aberrations on spatial frequency domain measurements.
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Affiliation(s)
- Motasam Majedy
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Nandan K. Das
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Johannes Johansson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Rolf B. Saager
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
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Spatial-Frequency Domain Imaging: An Emerging Depth-Varying and Wide-Field Technique for Optical Property Measurement of Biological Tissues. PHOTONICS 2021. [DOI: 10.3390/photonics8050162] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Measurement of optical properties is critical for understanding light-tissue interaction, properly interpreting measurement data, and gaining better knowledge of tissue physicochemical properties. However, conventional optical measuring techniques are limited in point measurement, which partly hinders the applications on characterizing spatial distribution and inhomogeneity of optical properties of biological tissues. Spatial-frequency domain imaging (SFDI), as an emerging non-contact, depth-varying and wide-field optical imaging technique, is capable of measuring the optical properties in a wide field-of-view on a pixel-by-pixel basis. This review first describes the typical SFDI system and the principle for estimating optical properties using the SFDI technique. Then, the applications of SFDI in the fields of biomedicine, as well as food and agriculture, are reviewed, including burn assessment, skin tissue evaluation, tumor tissue detection, brain tissue monitoring, and quality evaluation of agro-products. Finally, a discussion on the challenges and future perspectives of SFDI for optical property estimation is presented.
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Galeb HA, Wilkinson EL, Stowell AF, Lin H, Murphy ST, Martin‐Hirsch PL, Mort RL, Taylor AM, Hardy JG. Melanins as Sustainable Resources for Advanced Biotechnological Applications. GLOBAL CHALLENGES (HOBOKEN, NJ) 2021; 5:2000102. [PMID: 33552556 PMCID: PMC7857133 DOI: 10.1002/gch2.202000102] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/04/2020] [Indexed: 05/17/2023]
Abstract
Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.
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Affiliation(s)
- Hanaa A. Galeb
- Department of ChemistryLancaster UniversityLancasterLA1 4YBUK
- Department of ChemistryScience and Arts CollegeRabigh CampusKing Abdulaziz UniversityJeddah21577Saudi Arabia
| | - Emma L. Wilkinson
- Department of Biomedical and Life SciencesLancaster UniversityLancasterLA1 4YGUK
| | - Alison F. Stowell
- Department of Organisation, Work and TechnologyLancaster University Management SchoolLancaster UniversityLancasterLA1 4YXUK
| | - Hungyen Lin
- Department of EngineeringLancaster UniversityLancasterLA1 4YWUK
| | - Samuel T. Murphy
- Department of EngineeringLancaster UniversityLancasterLA1 4YWUK
- Materials Science InstituteLancaster UniversityLancasterLA1 4YBUK
| | - Pierre L. Martin‐Hirsch
- Lancashire Teaching Hospitals NHS TrustRoyal Preston HospitalSharoe Green LanePrestonPR2 9HTUK
| | - Richard L. Mort
- Department of Biomedical and Life SciencesLancaster UniversityLancasterLA1 4YGUK
| | - Adam M. Taylor
- Lancaster Medical SchoolLancaster UniversityLancasterLA1 4YWUK
| | - John G. Hardy
- Department of ChemistryLancaster UniversityLancasterLA1 4YBUK
- Materials Science InstituteLancaster UniversityLancasterLA1 4YBUK
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Belcastro L, Jonasson H, Strömberg T, Saager RB. Handheld multispectral imager for quantitative skin assessment in low-resource settings. JOURNAL OF BIOMEDICAL OPTICS 2020; 25:1-12. [PMID: 32755076 PMCID: PMC7399474 DOI: 10.1117/1.jbo.25.8.082702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 07/06/2020] [Indexed: 05/28/2023]
Abstract
SIGNIFICANCE Spatial frequency domain imaging (SFDI) is a quantitative imaging method to measure absorption and scattering of tissue, from which several chromophore concentrations (e.g., oxy-/deoxy-/meth-hemoglobin, melanin, and carotenoids) can be calculated. Employing a method to extract additional spectral bands from RGB components (that we named cross-channels), we designed a handheld SFDI device to account for these pigments, using low-cost, consumer-grade components for its implementation and characterization. AIM With only three broad spectral bands (red, green, blue, or RGB), consumer-grade devices are often too limited. We present a methodology to increase the number of spectral bands in SFDI devices that use RGB components without hardware modification. APPROACH We developed a compact low-cost RGB spectral imager using a color CMOS camera and LED-based mini projector. The components' spectral properties were characterized and additional cross-channel bands were calculated. An alternative characterization procedure was also developed that makes use of low-cost equipment, and its results were compared. The device performance was evaluated by measurements on tissue-simulating optical phantoms and in-vivo tissue. The measurements were compared with another quantitative spectroscopy method: spatial frequency domain spectroscopy (SFDS). RESULTS Out of six possible cross-channel bands, two were evaluated to be suitable for our application and were fully characterized (520 ± 20 nm; 556 ± 18 nm). The other four cross-channels presented a too low signal-to-noise ratio for this implementation. In estimating the optical properties of optical phantoms, the SFDI data have a strong linear correlation with the SFDS data (R2 = 0.987, RMSE = 0.006 for μa, R2 = 0.994, RMSE = 0.078 for μs'). CONCLUSIONS We extracted two additional spectral bands from a commercial RGB system at no cost. There was good agreement between our device and the research-grade SFDS system. The alternative characterization procedure we have presented allowed us to measure the spectral features of the system with an accuracy comparable to standard laboratory equipment.
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Affiliation(s)
- Luigi Belcastro
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Hanna Jonasson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Tomas Strömberg
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Rolf B. Saager
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
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10
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Yao X, Li S, He S. DUAL-MODE HYPERSPECTRAL BIO-IMAGER WITH A CONJUGATED CAMERA FOR QUICK OBJECT-SELECTION AND FOCUSING. ACTA ACUST UNITED AC 2020. [DOI: 10.2528/pier20080308] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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11
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Gioux S, Mazhar A, Cuccia DJ. Spatial frequency domain imaging in 2019: principles, applications, and perspectives. JOURNAL OF BIOMEDICAL OPTICS 2019; 24:1-18. [PMID: 31222987 PMCID: PMC6995958 DOI: 10.1117/1.jbo.24.7.071613] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 05/09/2019] [Indexed: 05/20/2023]
Abstract
Spatial frequency domain imaging (SFDI) has witnessed very rapid growth over the last decade, owing to its unique capabilities for imaging optical properties and chromophores over a large field-of-view and in a rapid manner. We provide a comprehensive review of the principles of this imaging method as of 2019, review the modeling of light propagation in this domain, describe acquisition methods, provide an understanding of the various implementations and their practical limitations, and finally review applications that have been published in the literature. Importantly, we also introduce a group effort by several key actors in the field for the dissemination of SFDI, including publications, advice in hardware and implementations, and processing code, all freely available online.
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Affiliation(s)
- Sylvain Gioux
- University of Strasbourg, ICube Laboratory, Strasbourg, France
- Address all correspondence to Sylvain Gioux, E-mail:
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12
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Erfanzadeh M, Zhu Q. Photoacoustic imaging with low-cost sources; A review. PHOTOACOUSTICS 2019; 14:1-11. [PMID: 30923674 PMCID: PMC6423351 DOI: 10.1016/j.pacs.2019.01.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 12/28/2018] [Accepted: 01/24/2019] [Indexed: 05/04/2023]
Abstract
Benefitting from advantages of optical and ultrasound imaging, photoacoustic imaging (PAI) has demonstrated potentials in a wide range of medical applications. In order to facilitate clinical applications of PAI and encourage its application in low-resource settings, research on low-cost photoacoustic imaging with inexpensive optical sources has gained attention. Here, we review the advances made in photoacoustic imaging with low-cost sources.
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Affiliation(s)
- Mohsen Erfanzadeh
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - Quing Zhu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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13
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Gioux S, Mazhar A, Cuccia DJ. Spatial frequency domain imaging in 2019: principles, applications, and perspectives. JOURNAL OF BIOMEDICAL OPTICS 2019. [PMID: 31222987 DOI: 10.1117/1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Spatial frequency domain imaging (SFDI) has witnessed very rapid growth over the last decade, owing to its unique capabilities for imaging optical properties and chromophores over a large field-of-view and in a rapid manner. We provide a comprehensive review of the principles of this imaging method as of 2019, review the modeling of light propagation in this domain, describe acquisition methods, provide an understanding of the various implementations and their practical limitations, and finally review applications that have been published in the literature. Importantly, we also introduce a group effort by several key actors in the field for the dissemination of SFDI, including publications, advice in hardware and implementations, and processing code, all freely available online.
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Affiliation(s)
- Sylvain Gioux
- University of Strasbourg, ICube Laboratory, Strasbourg, France
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14
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Abstract
Despite our understanding that the microvasculature plays a multifaceted role in the development and progression of various conditions, we know little about the extent of this involvement. A need exists for non-invasive, clinically meaningful imaging modalities capable of elucidating microvascular information to aid in our understanding of disease, and to aid in the diagnosis/monitoring of disease for more patient-specific care. In this review article, a number of imaging techniques are summarized that have been utilized to investigate the microvasculature of skin, along with their advantages, disadvantages and future perspectives in preclinical and clinical settings. These techniques include dermoscopy, capillaroscopy, Doppler sonography, laser Doppler flowmetry (LDF) and perfusion imaging, laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), including its Doppler and dynamic variant and the more recently developed OCT angiography (OCTA), photoacoustic imaging, and spatial frequency domain imaging (SFDI). Attention is largely, but not exclusively, placed on optical imaging modalities that use intrinsic optical signals to contrast the microvasculature. We conclude that whilst each imaging modality has been successful in filling a particular niche, there is no one, all-encompassing modality without inherent flaws. Therefore, the future of cutaneous microvascular imaging may lie in utilizing a multi-modal approach that will counter the disadvantages of individual systems to synergistically augment our imaging capabilities.
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Affiliation(s)
- Anthony J Deegan
- Department of Bioengineering, University of Washington, 3720 15th Ave. NE., Seattle, WA 98195, United States of America
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15
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Saager RB, Rowland RA, Baldado ML, Kennedy GT, Bernal NP, Ponticorvo A, Christy RJ, Durkin AJ. Impact of hemoglobin breakdown products in the spectral analysis of burn wounds using spatial frequency domain spectroscopy. JOURNAL OF BIOMEDICAL OPTICS 2019; 24:1-4. [PMID: 30724041 PMCID: PMC6398280 DOI: 10.1117/1.jbo.24.2.020501] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/15/2019] [Indexed: 05/23/2023]
Abstract
Burn wounds and wound healing invoke several biological processes that may complicate the interpretation of spectral imaging data. Through analysis of spatial frequency domain spectroscopy data (450 to 1000 nm) obtained from longitudinal investigations using a graded porcine burn wound healing model, we have identified features in the absorption spectrum that appear to suggest the presence of hemoglobin breakdown products, e.g., methemoglobin. Our results show that the calculated concentrations of methemoglobin directly correlate with burn severity, 24 h after the injury. In addition, tissue parameters such as oxygenation (StO2) and water fraction may be underestimated by 20% and 78%, respectively, if methemoglobin is not included in the spectral analysis.
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Affiliation(s)
- Rolf B Saager
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Rebecca A Rowland
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Melissa L Baldado
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Gordon T Kennedy
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Nicole P Bernal
- UC Irvine Regional Burn Center, Department of Surgery, Orange, California, United States
| | - Adrien Ponticorvo
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Robert J Christy
- United States Army Institute of Surgical Research, Burn and Soft Tissue Injury, San Antonio, Texas, United States
| | - Anthony J Durkin
- University of California Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
- University of California Irvine, Department of Biomedical Engineering, Irvine, California, United States
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16
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Saager RB, Baldado ML, Rowland RA, Kelly KM, Durkin AJ. Method using in vivo quantitative spectroscopy to guide design and optimization of low-cost, compact clinical imaging devices: emulation and evaluation of multispectral imaging systems. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-12. [PMID: 29633609 PMCID: PMC5890028 DOI: 10.1117/1.jbo.23.4.046002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 03/16/2018] [Indexed: 05/30/2023]
Abstract
With recent proliferation in compact and/or low-cost clinical multispectral imaging approaches and commercially available components, questions remain whether they adequately capture the requisite spectral content of their applications. We present a method to emulate the spectral range and resolution of a variety of multispectral imagers, based on in-vivo data acquired from spatial frequency domain spectroscopy (SFDS). This approach simulates spectral responses over 400 to 1100 nm. Comparing emulated data with full SFDS spectra of in-vivo tissue affords the opportunity to evaluate whether the sparse spectral content of these imagers can (1) account for all sources of optical contrast present (completeness) and (2) robustly separate and quantify sources of optical contrast (crosstalk). We validate the approach over a range of tissue-simulating phantoms, comparing the SFDS-based emulated spectra against measurements from an independently characterized multispectral imager. Emulated results match the imager across all phantoms (<3 % absorption, <1 % reduced scattering). In-vivo test cases (burn wounds and photoaging) illustrate how SFDS can be used to evaluate different multispectral imagers. This approach provides an in-vivo measurement method to evaluate the performance of multispectral imagers specific to their targeted clinical applications and can assist in the design and optimization of new spectral imaging devices.
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Affiliation(s)
- Rolf B. Saager
- University of California, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Melissa L. Baldado
- University of California, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Rebecca A. Rowland
- University of California, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Kristen M. Kelly
- University of California, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
- University of California, Department of Dermatology, Irvine, California, United States
| | - Anthony J. Durkin
- University of California, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
- University of California, Department of Biomedical Engineering, Irvine, California, United States
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17
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Pera V, Karrobi K, Tabassum S, Teng F, Roblyer D. Optical property uncertainty estimates for spatial frequency domain imaging. BIOMEDICAL OPTICS EXPRESS 2018; 9:661-678. [PMID: 29552403 PMCID: PMC5854069 DOI: 10.1364/boe.9.000661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/21/2017] [Accepted: 01/08/2018] [Indexed: 05/02/2023]
Abstract
Spatial frequency domain imaging (SFDI) is a wide-field diffuse optical imaging modality that has attracted considerable interest in recent years. Typically, diffuse reflectance measurements of spatially modulated light are used to quantify the optical absorption and reduced scattering coefficients of tissue, and with these, chromophore concentrations are extracted. However, uncertainties in estimated absorption and reduced scattering coefficients are rarely reported, and we know of no method capable of providing these when look-up table (LUT) algorithms are used to recover the optical properties. We present a method to generate optical property uncertainty estimates from knowledge of diffuse reflectance measurement errors. By employing the Cramér-Rao bound, we can quickly and efficiently explore theoretical SFDI performance as a function of spatial frequencies and sample optical properties, allowing us to optimize spatial frequency selection for a given application. In practice, we can also obtain useful uncertainty estimates for optical properties recovered with a two-frequency LUT algorithm, as we demonstrate with tissue-simulating phantom and in vivo experiments. Finally, we illustrate how absorption coefficient uncertainties can be propagated forward to yield uncertainties for chromophore concentrations, which could significantly impact the interpretation of experimental results.
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Affiliation(s)
- Vivian Pera
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215,
USA
| | - Kavon Karrobi
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215,
USA
| | - Syeda Tabassum
- Department of Electrical and Computer Engineering, Boston University, 8 Saint Mary’s Street, Boston, MA 02215,
USA
| | - Fei Teng
- Department of Electrical and Computer Engineering, Boston University, 8 Saint Mary’s Street, Boston, MA 02215,
USA
| | - Darren Roblyer
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215,
USA
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