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Tweel JED, Ecclestone BR, Boktor M, Dinakaran D, Mackey JR, Reza PH. Automated Whole Slide Imaging for Label-Free Histology Using Photon Absorption Remote Sensing Microscopy. IEEE Trans Biomed Eng 2024; 71:1901-1912. [PMID: 38231822 DOI: 10.1109/tbme.2024.3355296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
OBJECTIVE Pathologists rely on histochemical stains to impart contrast in thin translucent tissue samples, revealing tissue features necessary for identifying pathological conditions. However, the chemical labeling process is destructive and often irreversible or challenging to undo, imposing practical limits on the number of stains that can be applied to the same tissue section. Here we present an automated label-free whole slide scanner using a PARS microscope designed for imaging thin, transmissible samples. METHODS Peak SNR and in-focus acquisitions are achieved across entire tissue sections using the scattering signal from the PARS detection beam to measure the optimal focal plane. Whole slide images (WSI) are seamlessly stitched together using a custom contrast leveling algorithm. Identical tissue sections are subsequently H&E stained and brightfield imaged. The one-to-one WSIs from both modalities are visually and quantitatively compared. RESULTS PARS WSIs are presented at standard 40x magnification in malignant human breast and skin samples. We show correspondence of subcellular diagnostic details in both PARS and H&E WSIs and demonstrate virtual H&E staining of an entire PARS WSI. The one-to-one WSI from both modalities show quantitative similarity in nuclear features and structural information. CONCLUSION PARS WSIs are compatible with existing digital pathology tools, and samples remain suitable for histochemical, immunohistochemical, and other staining techniques. SIGNIFICANCE This work is a critical advance for integrating label-free optical methods into standard histopathology workflows.
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Lu Y, Sun Y, Shen Z, Xu X, Ma T, Peng C, Li F, Ning C, Wang J, Liu S, Liu Z, Xu L, Liu W. Thermal-tagging photoacoustic remote sensing flowmetry. OPTICS LETTERS 2024; 49:1725-1728. [PMID: 38560847 DOI: 10.1364/ol.521564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 03/07/2024] [Indexed: 04/04/2024]
Abstract
Ultrasound coupling is one of the critical challenges for traditional photoacoustic (or optoacoustic) microscopy (PAM) techniques transferred to the clinical examination of chronic wounds and open tissues. A promising alternative potential solution for breaking the limitation of ultrasound coupling in PAM is photoacoustic remote sensing (PARS), which implements all-optical non-interferometric photoacoustic measurements. Functional imaging of PARS microscopy was demonstrated from the aspects of histopathology and oxygen metabolism, while its performance in hemodynamic quantification remains unexplored. In this Letter, we present an all-optical thermal-tagging flowmetry approach for PARS microscopy and demonstrate it with comprehensive mathematical modeling and ex vivo and in vivo experimental validations. Experimental results demonstrated that the detectable range of the blood flow rate was from 0 to 12 mm/s with a high accuracy (measurement error:±1.2%) at 10-kHz laser pulse repetition rate. The proposed all-optical thermal-tagging flowmetry offers an effective alternative approach for PARS microscopy realizing non-contact dye-free hemodynamic imaging.
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Hirasawa T, Tachi K, Ishikawa T, Miyashita M, Ito K, Ishihara M. Photoacoustic microscopy for real-time monitoring of near-infrared optical absorbers inside biological tissue. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:S11527. [PMID: 38464883 PMCID: PMC10924425 DOI: 10.1117/1.jbo.29.s1.s11527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 02/09/2024] [Accepted: 02/13/2024] [Indexed: 03/12/2024]
Abstract
Significance We developed a high-speed optical-resolution photoacoustic microscopy (OR-PAM) system using a high-repetition-rate supercontinuum (SC) light source and a two-axes Galvano scanner. The OR-PAM system enabled real-time imaging of optical absorbers inside biological tissues with excellent excitation wavelength tunability. Aim In the near-infrared (NIR) wavelength range, high-speed OR-PAM faces limitations due to the lack of wavelength-tunable light sources. Our study aimed to enable high-speed OR-PAM imaging of various optical absorbers, including NIR contrast agents, and validate the performance of high-speed OR-PAM in the detection of circulating tumor cells (CTCs). Approach A high-repetition nanosecond pulsed SC light source was used for OR-PAM. The excitation wavelength was adjusted by bandpass filtering of broadband light pulses produced by an SC light source. Phantom and in vivo experiments were performed to detect tumor cells stained with an NIR contrast agent within flowing blood samples. Results The newly developed high-speed OR-PAM successfully detected stained cells both in the phantom and in vivo. The phantom experiment confirmed the correlation between the tumor cell detection rate and tumor cell concentration in the blood sample. Conclusions The high-speed OR-PAM effectively detected stained tumor cells. Combining high-speed OR-PAM with molecular probes that stain tumor cells in vivo enables in vivo CTC detection.
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Affiliation(s)
- Takeshi Hirasawa
- National Defense Medical College, Department of Medical Engineering, Tokorozawa, Japan
| | - Kazuyoshi Tachi
- National Defense Medical College, Department of Medical Engineering, Tokorozawa, Japan
- National Defense Medical College, Department of Urology, Tokorozawa, Japan
| | - Tomohiro Ishikawa
- National Defense Medical College, Department of Medical Engineering, Tokorozawa, Japan
| | - Manami Miyashita
- National Defense Medical College, Department of Medical Engineering, Tokorozawa, Japan
| | - Keiichi Ito
- National Defense Medical College, Department of Urology, Tokorozawa, Japan
| | - Miya Ishihara
- National Defense Medical College, Department of Medical Engineering, Tokorozawa, Japan
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Zhang Y, Xu J, Liang J, Ke Y, Ma X, Li S, Ye J, Huang L, Pan Z, Yao T, Leng J, Zhou P. Broadband tunable Raman fiber laser with monochromatic pump. OPTICS EXPRESS 2023; 31:30542-30549. [PMID: 37710594 DOI: 10.1364/oe.497609] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 08/23/2023] [Indexed: 09/16/2023]
Abstract
Raman fiber laser (RFL) has been widely adopted in astronomy, optical sensing, imaging, and communication due to its unique advantages of flexible wavelength and broadband gain spectrum. Conventional RFLs are generally based on silica fiber. Here, we demonstrate that the phosphosilicate fiber has a broader Raman gain spectrum as compared to the common silica fiber, making it a better choice for broadband Raman conversion. By using the phosphosilicate fiber as gain medium, we propose and build a tunable RFL, and compare its operation bandwidth with a silica fiber-based RFL. The silica fiber-based RFL can operate within the Raman shift range of 4.9 THz (9.8-14.7 THz), whereas in the phosphosilicate fiber-based RFL, efficient lasing is achieved over the Raman shift range of 13.7 THz (3.5-17.2 THz). The operation bandwidths of the two RFLs are also calculated theoretically. The simulation results agree well with experimental data, where the operation bandwidth of the phosphosilicate fiber-based RFL is more than twice of that of the silica fiber-based RFL. This work reveals the phosphosilicate fiber's unique advantage in broadband Raman conversion, which has great potential in increasing the reach and capacity of optical communication systems.
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Zhang Y, Chen J, Zhang J, Zhu J, Liu C, Sun H, Wang L. Super-Low-Dose Functional and Molecular Photoacoustic Microscopy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2302486. [PMID: 37310419 PMCID: PMC10427362 DOI: 10.1002/advs.202302486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/21/2023] [Indexed: 06/14/2023]
Abstract
Photoacoustic microscopy can image many biological molecules and nano-agents in vivo via low-scattering ultrasonic sensing. Insufficient sensitivity is a long-standing obstacle for imaging low-absorbing chromophores with less photobleaching or toxicity, reduced perturbation to delicate organs, and more choices of low-power lasers. Here, the photoacoustic probe design is collaboratively optimized and a spectral-spatial filter is implemented. A multi-spectral super-low-dose photoacoustic microscopy (SLD-PAM) is presented that improves the sensitivity by ≈33 times. SLD-PAM can visualize microvessels and quantify oxygen saturation in vivo with ≈1% of the maximum permissible exposure, dramatically reducing potential phototoxicity or perturbation to normal tissue function, especially in imaging of delicate tissues, such as the eye and the brain. Capitalizing on the high sensitivity, direct imaging of deoxyhemoglobin concentration is achieved without spectral unmixing, avoiding wavelength-dependent errors and computational noises. With reduced laser power, SLD-PAM can reduce photobleaching by ≈85%. It is also demonstrated that SLD-PAM achieves similar molecular imaging quality using 80% fewer contrast agents. Therefore, SLD-PAM enables the use of a broader range of low-absorbing nano-agents, small molecules, and genetically encoded biomarkers, as well as more types of low-power light sources in wide spectra. It is believed that SLD-PAM offers a powerful tool for anatomical, functional, and molecular imaging.
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Affiliation(s)
- Yachao Zhang
- Department of Biomedical EngineeringCity University of Hong KongHong KongSAR999077China
| | - Jiangbo Chen
- Department of Biomedical EngineeringCity University of Hong KongHong KongSAR999077China
| | - Jie Zhang
- Department of Chemistry and COSADAF (Centre of Super‐Diamond and Advanced Films)City University of Hong KongHong KongSAR999077China
| | - Jingyi Zhu
- Department of Biomedical EngineeringCity University of Hong KongHong KongSAR999077China
| | - Chao Liu
- Department of Biomedical EngineeringCity University of Hong KongHong KongSAR999077China
| | - Hongyan Sun
- Department of Chemistry and COSADAF (Centre of Super‐Diamond and Advanced Films)City University of Hong KongHong KongSAR999077China
| | - Lidai Wang
- Department of Biomedical EngineeringCity University of Hong KongHong KongSAR999077China
- City University of Hong Kong Shenzhen Research InstituteShenzhenChina518057
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Qu Z, Liu C, Zhu J, Zhang Y, Zhou Y, Wang L. Two-step proximal gradient descent algorithm for photoacoustic signal unmixing. PHOTOACOUSTICS 2022; 27:100379. [PMID: 35722270 PMCID: PMC9198964 DOI: 10.1016/j.pacs.2022.100379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/22/2022] [Accepted: 06/07/2022] [Indexed: 05/02/2023]
Abstract
Photoacoustic microscopy uses multiple wavelengths to measure concentrations of different absorbers. The speed of sound limits the shortest wavelength switching time to sub-microseconds, which is a bottleneck for high-speed broad-spectrum imaging. Via computational separation of overlapped signals, we can break the sound-speed limit on the wavelength switching time. This paper presents a new signal unmixing algorithm named two-step proximal gradient descent. It is advantageous in separating multiple wavelengths with long overlapping and high noise. In the simulation, we can unmix up to nine overlapped signals and successfully separate three overlapped signals with 12-ns delay and 15.9-dB signal-to-noise ratio. We apply this technique to separate three-wavelength photoacoustic images in microvessels. In vivo results show that the algorithm can successfully unmix overlapped multi-wavelength photoacoustic signals, and the unmixed data can improve accuracy in oxygen saturation imaging.
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Affiliation(s)
- Zheng Qu
- City University of Hong Kong, Department of Biomedical Engineering, Kowloon, Hong Kong, China
| | - Chao Liu
- City University of Hong Kong, Department of Biomedical Engineering, Kowloon, Hong Kong, China
| | - Jingyi Zhu
- City University of Hong Kong, Department of Biomedical Engineering, Kowloon, Hong Kong, China
| | - Yachao Zhang
- City University of Hong Kong, Department of Biomedical Engineering, Kowloon, Hong Kong, China
| | - Yingying Zhou
- City University of Hong Kong, Department of Biomedical Engineering, Kowloon, Hong Kong, China
| | - Lidai Wang
- City University of Hong Kong, Department of Biomedical Engineering, Kowloon, Hong Kong, China
- City University of Hong Kong Shenzhen Research Institute, Yuexing Yi Dao, Shenzhen, Guang Dong 518057, China
- Corresponding author at: City University of Hong Kong, Department of Biomedical Engineering, Kowloon, .Hong Kong, China
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Functional photoacoustic microscopy of hemodynamics: a review. Biomed Eng Lett 2022; 12:97-124. [PMID: 35529339 PMCID: PMC9046529 DOI: 10.1007/s13534-022-00220-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 01/24/2022] [Accepted: 01/30/2022] [Indexed: 12/19/2022] Open
Abstract
Functional blood imaging can reflect tissue metabolism and organ viability, which is important for life science and biomedical studies. However, conventional imaging modalities either cannot provide sufficient contrast or cannot support simultaneous multi-functional imaging for hemodynamics. Photoacoustic imaging, as a hybrid imaging modality, can provide sufficient optical contrast and high spatial resolution, making it a powerful tool for in vivo vascular imaging. By using the optical-acoustic confocal alignment, photoacoustic imaging can even provide subcellular insight, referred as optical-resolution photoacoustic microscopy (OR-PAM). Based on a multi-wavelength laser source and developed the calculation methods, OR-PAM can provide multi-functional hemodynamic microscopic imaging of the total hemoglobin concentration (CHb), oxygen saturation (sO2), blood flow (BF), partial oxygen pressure (pO2), oxygen extraction fraction, and metabolic rate of oxygen (MRO2). This concise review aims to systematically introduce the principles and methods to acquire various functional parameters for hemodynamics by photoacoustic microscopy in recent studies, with characteristics and advantages comparison, typical biomedical applications introduction, and future outlook discussion.
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In-vivo functional and structural retinal imaging using multiwavelength photoacoustic remote sensing microscopy. Sci Rep 2022; 12:4562. [PMID: 35296738 PMCID: PMC8927130 DOI: 10.1038/s41598-022-08508-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 03/08/2022] [Indexed: 11/16/2022] Open
Abstract
Many important eye diseases as well as systemic disorders manifest themselves in the retina. Retinal imaging technologies are rapidly growing and can provide ever-increasing amounts of information about the structure, function, and molecular composition of retinal tissue in-vivo. Photoacoustic remote sensing (PARS) is a novel imaging modality based on all-optical detection of photoacoustic signals, which makes it suitable for a wide range of medical applications. In this study, PARS is applied for in-vivo imaging of the retina and estimating oxygen saturation in the retinal vasculature. To our knowledge, this is the first time that a non-contact photoacoustic imaging technique is applied for in-vivo imaging of the retina. Here, optical coherence tomography is also used as a well-established retinal imaging technique to navigate the PARS imaging beams and demonstrate the capabilities of the optical imaging setup. The system is applied for in-vivo imaging of both microanatomy and the microvasculature of the retina. The developed system has the potential to advance the understanding of the ocular environment and to help in monitoring of ophthalmic diseases.
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